This tutorial will cover how to implement directional shadow maps using OpenGL 4.0 and GLSL.
We will start with the code from the original shadow mapping tutorial number 41 and modify it to handle directional lighting.
Directional shadow maps are generally used to simulate shadows that would be created by sun light.
Uses include where sunlight comes through a window, or shadows for objects on terrain, and other lighting methods that require a directional light instead of positional.
To implement directional shadow maps, we will need to just make two changes to our already existing positional shadow map code.
The first change will be to modify the light shading code to handle directional lighting instead of positional lighting.
And the second change is to use an orthographic projection matrix instead of our regular projection matrix.
The orthographic matrix gives us a square projection which fits with directional lighting instead of a trapezoid style projection that positional lights use.
Framework
The framework remains the same for this tutorial as we have not added any additional classes.
We will start the code section of the tutorial by looking at the updated GLSL shadow shader.
Shadow.vs
The vertex shader has had the positional lighting code removed from it.
Just the code that directional lighting and shadow maps need has remained.
////////////////////////////////////////////////////////////////////////////////
// Filename: shadow.vs
////////////////////////////////////////////////////////////////////////////////
#version 400
/////////////////////
// INPUT VARIABLES //
/////////////////////
in vec3 inputPosition;
in vec2 inputTexCoord;
in vec3 inputNormal;
//////////////////////
// OUTPUT VARIABLES //
//////////////////////
out vec2 texCoord;
out vec3 normal;
out vec4 lightViewPosition;
///////////////////////
// UNIFORM VARIABLES //
///////////////////////
uniform mat4 worldMatrix;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;
uniform mat4 lightViewMatrix;
uniform mat4 lightProjectionMatrix;
////////////////////////////////////////////////////////////////////////////////
// Vertex Shader
////////////////////////////////////////////////////////////////////////////////
void main(void)
{
// Calculate the position of the vertex against the world, view, and projection matrices.
gl_Position = vec4(inputPosition, 1.0f) * worldMatrix;
gl_Position = gl_Position * viewMatrix;
gl_Position = gl_Position * projectionMatrix;
// Store the position of the vertice as viewed by the projection view point in a separate variable.
lightViewPosition = vec4(inputPosition, 1.0f) * worldMatrix;
lightViewPosition = lightViewPosition * lightViewMatrix;
lightViewPosition = lightViewPosition * lightProjectionMatrix;
// Store the texture coordinates for the pixel shader.
texCoord = inputTexCoord;
// Calculate the normal vector against the world matrix only.
normal = inputNormal * mat3(worldMatrix);
// Normalize the normal vector.
normal = normalize(normal);
}
Shadow.ps
////////////////////////////////////////////////////////////////////////////////
// Filename: shadow.ps
////////////////////////////////////////////////////////////////////////////////
#version 400
/////////////////////
// INPUT VARIABLES //
/////////////////////
in vec2 texCoord;
in vec3 normal;
in vec4 lightViewPosition;
//////////////////////
// OUTPUT VARIABLES //
//////////////////////
out vec4 outputColor;
///////////////////////
// UNIFORM VARIABLES //
///////////////////////
uniform sampler2D shaderTexture;
uniform sampler2D depthMapTexture;
uniform vec4 ambientColor;
uniform vec4 diffuseColor;
uniform float bias;
We now use the light direction instead of light position for directional light calculations.
uniform vec3 lightDirection;
////////////////////////////////////////////////////////////////////////////////
// Pixel Shader
////////////////////////////////////////////////////////////////////////////////
void main(void)
{
vec4 color;
vec2 projectTexCoord;
float depthValue;
float lightDepthValue;
float lightIntensity;
vec4 textureColor;
vec3 lightDir;
The pixel shader will need to invert the light direction.
// Invert the light direction.
lightDir = -lightDirection;
// Set the default output color to the ambient light value for all pixels.
color = ambientColor;
// Calculate the projected texture coordinates.
projectTexCoord.x = lightViewPosition.x / lightViewPosition.w / 2.0f + 0.5f;
projectTexCoord.y = lightViewPosition.y / lightViewPosition.w / 2.0f + 0.5f;
// Determine if the projected coordinates are in the 0 to 1 range. If so then this pixel is in the view of the light.
if((clamp(projectTexCoord.x, 0.0, 1.0) == projectTexCoord.x) && (clamp(projectTexCoord.y, 0.0, 1.0) == projectTexCoord.y))
{
// Sample the shadow map depth value from the depth texture using the sampler at the projected texture coordinate location.
depthValue = texture(depthMapTexture, projectTexCoord).r;
// Calculate the depth of the light.
lightDepthValue = lightViewPosition.z / lightViewPosition.w;
// Subtract the bias from the lightDepthValue.
lightDepthValue = lightDepthValue - bias;
// Compare the depth of the shadow map value and the depth of the light to determine whether to shadow or to light this pixel.
// If the light is in front of the object then light the pixel, if not then shadow this pixel since an object (occluder) is casting a shadow on it.
if(lightDepthValue < depthValue)
{
We calculate directional lighting now instead of positional.
// Calculate the amount of light on this pixel.
lightIntensity = clamp(dot(normal, lightDir), 0.0f, 1.0f);
if(lightIntensity > 0.0f)
{
// Determine the final diffuse color based on the diffuse color and the amount of light intensity.
color += (diffuseColor * lightIntensity);
// Saturate the final light color of both lights.
color = clamp(color, 0.0f, 1.0f);
}
}
}
I have added an additional else clause to handle the case where objects are not inside the shadow map area.
If we find that a pixel is outside this region then we do just regular directional lighting.
Note that you can comment out this else clause to see exactly where your shadow map range begins and ends.
else
{
// If this is outside the area of shadow map range then draw things normally with regular lighting.
lightIntensity = clamp(dot(normal, lightDir), 0.0f, 1.0f);
if(lightIntensity > 0.0f)
{
color += (diffuseColor * lightIntensity);
color = clamp(color, 0.0f, 1.0f);
}
}
// Sample the pixel color from the texture using the sampler at this texture coordinate location.
textureColor = texture(shaderTexture, texCoord);
// Combine the light and texture color.
outputColor = color * textureColor;
}
Shadowshaderclass.h
////////////////////////////////////////////////////////////////////////////////
// Filename: shadowshaderclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _SHADOWSHADERCLASS_H_
#define _SHADOWSHADERCLASS_H_
//////////////
// INCLUDES //
//////////////
#include <iostream>
using namespace std;
///////////////////////
// MY CLASS INCLUDES //
///////////////////////
#include "openglclass.h"
////////////////////////////////////////////////////////////////////////////////
// Class name: ShadowShaderClass
////////////////////////////////////////////////////////////////////////////////
class ShadowShaderClass
{
public:
ShadowShaderClass();
ShadowShaderClass(const ShadowShaderClass&);
~ShadowShaderClass();
bool Initialize(OpenGLClass*);
void Shutdown();
bool SetShaderParameters(float*, float*, float*, float*, float*, float*, float*, float*, float);
private:
bool InitializeShader(char*, char*);
void ShutdownShader();
char* LoadShaderSourceFile(char*);
void OutputShaderErrorMessage(unsigned int, char*);
void OutputLinkerErrorMessage(unsigned int);
private:
OpenGLClass* m_OpenGLPtr;
unsigned int m_vertexShader;
unsigned int m_fragmentShader;
unsigned int m_shaderProgram;
};
#endif
Shadowshaderclass.cpp
////////////////////////////////////////////////////////////////////////////////
// Filename: shadowshaderclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "shadowshaderclass.h"
ShadowShaderClass::ShadowShaderClass()
{
m_OpenGLPtr = 0;
}
ShadowShaderClass::ShadowShaderClass(const ShadowShaderClass& other)
{
}
ShadowShaderClass::~ShadowShaderClass()
{
}
bool ShadowShaderClass::Initialize(OpenGLClass* OpenGL)
{
char vsFilename[128];
char psFilename[128];
bool result;
// Store the pointer to the OpenGL object.
m_OpenGLPtr = OpenGL;
// Set the location and names of the shader files.
strcpy(vsFilename, "../Engine/shadow.vs");
strcpy(psFilename, "../Engine/shadow.ps");
// Initialize the vertex and pixel shaders.
result = InitializeShader(vsFilename, psFilename);
if(!result)
{
return false;
}
return true;
}
void ShadowShaderClass::Shutdown()
{
// Shutdown the shader.
ShutdownShader();
// Release the pointer to the OpenGL object.
m_OpenGLPtr = 0;
return;
}
bool ShadowShaderClass::InitializeShader(char* vsFilename, char* fsFilename)
{
const char* vertexShaderBuffer;
const char* fragmentShaderBuffer;
int status;
// Load the vertex shader source file into a text buffer.
vertexShaderBuffer = LoadShaderSourceFile(vsFilename);
if(!vertexShaderBuffer)
{
return false;
}
// Load the fragment shader source file into a text buffer.
fragmentShaderBuffer = LoadShaderSourceFile(fsFilename);
if(!fragmentShaderBuffer)
{
return false;
}
// Create a vertex and fragment shader object.
m_vertexShader = m_OpenGLPtr->glCreateShader(GL_VERTEX_SHADER);
m_fragmentShader = m_OpenGLPtr->glCreateShader(GL_FRAGMENT_SHADER);
// Copy the shader source code strings into the vertex and fragment shader objects.
m_OpenGLPtr->glShaderSource(m_vertexShader, 1, &vertexShaderBuffer, NULL);
m_OpenGLPtr->glShaderSource(m_fragmentShader, 1, &fragmentShaderBuffer, NULL);
// Release the vertex and fragment shader buffers.
delete [] vertexShaderBuffer;
vertexShaderBuffer = 0;
delete [] fragmentShaderBuffer;
fragmentShaderBuffer = 0;
// Compile the shaders.
m_OpenGLPtr->glCompileShader(m_vertexShader);
m_OpenGLPtr->glCompileShader(m_fragmentShader);
// Check to see if the vertex shader compiled successfully.
m_OpenGLPtr->glGetShaderiv(m_vertexShader, GL_COMPILE_STATUS, &status);
if(status != 1)
{
// If it did not compile then write the syntax error message out to a text file for review.
OutputShaderErrorMessage(m_vertexShader, vsFilename);
return false;
}
// Check to see if the fragment shader compiled successfully.
m_OpenGLPtr->glGetShaderiv(m_fragmentShader, GL_COMPILE_STATUS, &status);
if(status != 1)
{
// If it did not compile then write the syntax error message out to a text file for review.
OutputShaderErrorMessage(m_fragmentShader, fsFilename);
return false;
}
// Create a shader program object.
m_shaderProgram = m_OpenGLPtr->glCreateProgram();
// Attach the vertex and fragment shader to the program object.
m_OpenGLPtr->glAttachShader(m_shaderProgram, m_vertexShader);
m_OpenGLPtr->glAttachShader(m_shaderProgram, m_fragmentShader);
// Bind the shader input variables.
m_OpenGLPtr->glBindAttribLocation(m_shaderProgram, 0, "inputPosition");
m_OpenGLPtr->glBindAttribLocation(m_shaderProgram, 1, "inputTexCoord");
m_OpenGLPtr->glBindAttribLocation(m_shaderProgram, 2, "inputNormal");
// Link the shader program.
m_OpenGLPtr->glLinkProgram(m_shaderProgram);
// Check the status of the link.
m_OpenGLPtr->glGetProgramiv(m_shaderProgram, GL_LINK_STATUS, &status);
if(status != 1)
{
// If it did not link then write the syntax error message out to a text file for review.
OutputLinkerErrorMessage(m_shaderProgram);
return false;
}
return true;
}
void ShadowShaderClass::ShutdownShader()
{
// Detach the vertex and fragment shaders from the program.
m_OpenGLPtr->glDetachShader(m_shaderProgram, m_vertexShader);
m_OpenGLPtr->glDetachShader(m_shaderProgram, m_fragmentShader);
// Delete the vertex and fragment shaders.
m_OpenGLPtr->glDeleteShader(m_vertexShader);
m_OpenGLPtr->glDeleteShader(m_fragmentShader);
// Delete the shader program.
m_OpenGLPtr->glDeleteProgram(m_shaderProgram);
return;
}
char* ShadowShaderClass::LoadShaderSourceFile(char* filename)
{
FILE* filePtr;
char* buffer;
long fileSize, count;
int error;
// Open the shader file for reading in text modee.
filePtr = fopen(filename, "r");
if(filePtr == NULL)
{
return 0;
}
// Go to the end of the file and get the size of the file.
fseek(filePtr, 0, SEEK_END);
fileSize = ftell(filePtr);
// Initialize the buffer to read the shader source file into, adding 1 for an extra null terminator.
buffer = new char[fileSize + 1];
// Return the file pointer back to the beginning of the file.
fseek(filePtr, 0, SEEK_SET);
// Read the shader text file into the buffer.
count = fread(buffer, 1, fileSize, filePtr);
if(count != fileSize)
{
return 0;
}
// Close the file.
error = fclose(filePtr);
if(error != 0)
{
return 0;
}
// Null terminate the buffer.
buffer[fileSize] = '\0';
return buffer;
}
void ShadowShaderClass::OutputShaderErrorMessage(unsigned int shaderId, char* shaderFilename)
{
long count;
int logSize, error;
char* infoLog;
FILE* filePtr;
// Get the size of the string containing the information log for the failed shader compilation message.
m_OpenGLPtr->glGetShaderiv(shaderId, GL_INFO_LOG_LENGTH, &logSize);
// Increment the size by one to handle also the null terminator.
logSize++;
// Create a char buffer to hold the info log.
infoLog = new char[logSize];
// Now retrieve the info log.
m_OpenGLPtr->glGetShaderInfoLog(shaderId, logSize, NULL, infoLog);
// Open a text file to write the error message to.
filePtr = fopen("shader-error.txt", "w");
if(filePtr == NULL)
{
cout << "Error opening shader error message output file." << endl;
return;
}
// Write out the error message.
count = fwrite(infoLog, sizeof(char), logSize, filePtr);
if(count != logSize)
{
cout << "Error writing shader error message output file." << endl;
return;
}
// Close the file.
error = fclose(filePtr);
if(error != 0)
{
cout << "Error closing shader error message output file." << endl;
return;
}
// Notify the user to check the text file for compile errors.
cout << "Error compiling shader. Check shader-error.txt for error message. Shader filename: " << shaderFilename << endl;
return;
}
void ShadowShaderClass::OutputLinkerErrorMessage(unsigned int programId)
{
long count;
FILE* filePtr;
int logSize, error;
char* infoLog;
// Get the size of the string containing the information log for the failed shader compilation message.
m_OpenGLPtr->glGetProgramiv(programId, GL_INFO_LOG_LENGTH, &logSize);
// Increment the size by one to handle also the null terminator.
logSize++;
// Create a char buffer to hold the info log.
infoLog = new char[logSize];
// Now retrieve the info log.
m_OpenGLPtr->glGetProgramInfoLog(programId, logSize, NULL, infoLog);
// Open a file to write the error message to.
filePtr = fopen("linker-error.txt", "w");
if(filePtr == NULL)
{
cout << "Error opening linker error message output file." << endl;
return;
}
// Write out the error message.
count = fwrite(infoLog, sizeof(char), logSize, filePtr);
if(count != logSize)
{
cout << "Error writing linker error message output file." << endl;
return;
}
// Close the file.
error = fclose(filePtr);
if(error != 0)
{
cout << "Error closing linker error message output file." << endl;
return;
}
// Pop a message up on the screen to notify the user to check the text file for linker errors.
cout << "Error linking shader program. Check linker-error.txt for message." << endl;
return;
}
We now send in the direction of the light instead of the position of the light into the SetShaderParameters function.
bool ShadowShaderClass::SetShaderParameters(float* worldMatrix, float* viewMatrix, float* projectionMatrix, float* lightViewMatrix, float* lightProjectionMatrix,
float* diffuseColor, float* ambientColor, float* lightDirection, float bias)
{
float tpWorldMatrix[16], tpViewMatrix[16], tpProjectionMatrix[16], tpLightViewMatrix[16], tpLightProjectionMatrix[16];
int location;
// Transpose the matrices to prepare them for the shader.
m_OpenGLPtr->MatrixTranspose(tpWorldMatrix, worldMatrix);
m_OpenGLPtr->MatrixTranspose(tpViewMatrix, viewMatrix);
m_OpenGLPtr->MatrixTranspose(tpProjectionMatrix, projectionMatrix);
// Transpose the second view and projection matrices.
m_OpenGLPtr->MatrixTranspose(tpLightViewMatrix, lightViewMatrix);
m_OpenGLPtr->MatrixTranspose(tpLightProjectionMatrix, lightProjectionMatrix);
// Install the shader program as part of the current rendering state.
m_OpenGLPtr->glUseProgram(m_shaderProgram);
// Set the world matrix in the vertex shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "worldMatrix");
if(location == -1)
{
cout << "World matrix not set." << endl;
}
m_OpenGLPtr->glUniformMatrix4fv(location, 1, false, tpWorldMatrix);
// Set the view matrix in the vertex shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "viewMatrix");
if(location == -1)
{
cout << "View matrix not set." << endl;
}
m_OpenGLPtr->glUniformMatrix4fv(location, 1, false, tpViewMatrix);
// Set the projection matrix in the vertex shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "projectionMatrix");
if(location == -1)
{
cout << "Projection matrix not set." << endl;
}
m_OpenGLPtr->glUniformMatrix4fv(location, 1, false, tpProjectionMatrix);
// Set the light view matrix in the vertex shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "lightViewMatrix");
if(location == -1)
{
cout << "Light view matrix not set." << endl;
}
m_OpenGLPtr->glUniformMatrix4fv(location, 1, false, tpLightViewMatrix);
// Set the light projection matrix in the vertex shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "lightProjectionMatrix");
if(location == -1)
{
cout << "Light projection matrix not set." << endl;
}
m_OpenGLPtr->glUniformMatrix4fv(location, 1, false, tpLightProjectionMatrix);
The light direction is set instead of the light position.
// Set the light direction in the pixel shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "lightDirection");
if(location == -1)
{
cout << "Light direction not set." << endl;
}
m_OpenGLPtr->glUniform3fv(location, 1, lightDirection);
// Set the texture in the pixel shader to use the data from the first texture unit.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "shaderTexture");
if(location == -1)
{
cout << "Shader texture not set." << endl;
}
m_OpenGLPtr->glUniform1i(location, 0);
// Set the projection texture in the pixel shader to use the data from the second texture unit.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "depthMapTexture");
if(location == -1)
{
cout << "Depth map texture not set." << endl;
}
m_OpenGLPtr->glUniform1i(location, 1);
// Set the diffuse light color in the pixel shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "diffuseColor");
if(location == -1)
{
cout << "Diffuse color not set." << endl;
}
m_OpenGLPtr->glUniform4fv(location, 1, diffuseColor);
// Set the ambient light in the pixel shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "ambientColor");
if(location == -1)
{
cout << "Ambient color not set." << endl;
}
m_OpenGLPtr->glUniform4fv(location, 1, ambientColor);
// Set the shadow map bias in the pixel shader.
location = m_OpenGLPtr->glGetUniformLocation(m_shaderProgram, "bias");
if(location == -1)
{
cout << "Bias not set." << endl;
}
m_OpenGLPtr->glUniform1f(location, bias);
return true;
}
Lightclass.h
The light class has been modified to use a square orthographic projection instead of a regular trapezoid projection.
////////////////////////////////////////////////////////////////////////////////
// Filename: lightclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _LIGHTCLASS_H_
#define _LIGHTCLASS_H_
//////////////
// INCLUDES //
//////////////
#include <math.h>
////////////////////////////////////////////////////////////////////////////////
// Class name: LightClass
////////////////////////////////////////////////////////////////////////////////
class LightClass
{
private:
struct VectorType
{
float x, y, z;
};
public:
LightClass();
LightClass(const LightClass&);
~LightClass();
void SetDiffuseColor(float, float, float, float);
void SetDirection(float, float, float);
void SetAmbientLight(float, float, float, float);
void SetSpecularColor(float, float, float, float);
void SetSpecularPower(float);
void SetPosition(float, float, float);
void SetLookAt(float, float, float);
void GetDiffuseColor(float*);
void GetDirection(float*);
void GetAmbientLight(float*);
void GetSpecularColor(float*);
void GetSpecularPower(float&);
void GetPosition(float*);
void GenerateViewMatrix();
void GenerateProjectionMatrix(float, float);
void GenerateOrthoMatrix(float, float, float);
void GetViewMatrix(float*);
void GetProjectionMatrix(float*);
void GetOrthoMatrix(float*);
private:
void BuildMatrixLookAtLH(VectorType, VectorType, VectorType);
void BuildMatrixPerspectiveFovLH(float, float, float, float);
private:
float m_diffuseColor[4];
float m_direction[3];
float m_ambientLight[4];
float m_specularColor[4];
float m_specularPower;
float m_position[3];
float m_lookAt[3];
float m_viewMatrix[16], m_projectionMatrix[16], m_orthoMatrix[16];
};
#endif
Lightclass.cpp
////////////////////////////////////////////////////////////////////////////////
// Filename: lightclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "lightclass.h"
LightClass::LightClass()
{
}
LightClass::LightClass(const LightClass& other)
{
}
LightClass::~LightClass()
{
}
void LightClass::SetDiffuseColor(float red, float green, float blue, float alpha)
{
m_diffuseColor[0] = red;
m_diffuseColor[1] = green;
m_diffuseColor[2] = blue;
m_diffuseColor[3] = alpha;
return;
}
void LightClass::SetDirection(float x, float y, float z)
{
m_direction[0] = x;
m_direction[1] = y;
m_direction[2] = z;
return;
}
void LightClass::SetAmbientLight(float red, float green, float blue, float alpha)
{
m_ambientLight[0] = red;
m_ambientLight[1] = green;
m_ambientLight[2] = blue;
m_ambientLight[3] = alpha;
return;
}
void LightClass::SetSpecularColor(float red, float green, float blue, float alpha)
{
m_specularColor[0] = red;
m_specularColor[1] = green;
m_specularColor[2] = blue;
m_specularColor[3] = alpha;
return;
}
void LightClass::SetSpecularPower(float power)
{
m_specularPower = power;
return;
}
void LightClass::SetPosition(float x, float y, float z)
{
m_position[0] = x;
m_position[1] = y;
m_position[2] = z;
return;
}
void LightClass::SetLookAt(float x, float y, float z)
{
m_lookAt[0] = x;
m_lookAt[1] = y;
m_lookAt[2] = z;
return;
}
void LightClass::GetDiffuseColor(float* color)
{
color[0] = m_diffuseColor[0];
color[1] = m_diffuseColor[1];
color[2] = m_diffuseColor[2];
color[3] = m_diffuseColor[3];
return;
}
void LightClass::GetDirection(float* direction)
{
direction[0] = m_direction[0];
direction[1] = m_direction[1];
direction[2] = m_direction[2];
return;
}
void LightClass::GetAmbientLight(float* ambient)
{
ambient[0] = m_ambientLight[0];
ambient[1] = m_ambientLight[1];
ambient[2] = m_ambientLight[2];
ambient[3] = m_ambientLight[3];
return;
}
void LightClass::GetSpecularColor(float* specular)
{
specular[0] = m_specularColor[0];
specular[1] = m_specularColor[1];
specular[2] = m_specularColor[2];
specular[3] = m_specularColor[3];
return;
}
void LightClass::GetSpecularPower(float& power)
{
power = m_specularPower;
return;
}
void LightClass::GetPosition(float* position)
{
position[0] = m_position[0];
position[1] = m_position[1];
position[2] = m_position[2];
return;
}
void LightClass::GenerateViewMatrix()
{
VectorType up, position, lookAt;
// Setup the vectors.
up.x = 0.0f;
up.y = 1.0f;
up.z = 0.0f;
position.x = m_position[0];
position.y = m_position[1];
position.z = m_position[2];
lookAt.x = m_lookAt[0];
lookAt.y = m_lookAt[1];
lookAt.z = m_lookAt[2];
// Create the view matrix from the three vectors.
BuildMatrixLookAtLH(position, lookAt, up);
return;
}
void LightClass::BuildMatrixLookAtLH(VectorType position, VectorType lookAt, VectorType up)
{
VectorType zAxis, xAxis, yAxis;
float length, result1, result2, result3;
// zAxis = normal(lookAt - position)
zAxis.x = lookAt.x - position.x;
zAxis.y = lookAt.y - position.y;
zAxis.z = lookAt.z - position.z;
length = sqrt((zAxis.x * zAxis.x) + (zAxis.y * zAxis.y) + (zAxis.z * zAxis.z));
zAxis.x = zAxis.x / length;
zAxis.y = zAxis.y / length;
zAxis.z = zAxis.z / length;
// xAxis = normal(cross(up, zAxis))
xAxis.x = (up.y * zAxis.z) - (up.z * zAxis.y);
xAxis.y = (up.z * zAxis.x) - (up.x * zAxis.z);
xAxis.z = (up.x * zAxis.y) - (up.y * zAxis.x);
length = sqrt((xAxis.x * xAxis.x) + (xAxis.y * xAxis.y) + (xAxis.z * xAxis.z));
xAxis.x = xAxis.x / length;
xAxis.y = xAxis.y / length;
xAxis.z = xAxis.z / length;
// yAxis = cross(zAxis, xAxis)
yAxis.x = (zAxis.y * xAxis.z) - (zAxis.z * xAxis.y);
yAxis.y = (zAxis.z * xAxis.x) - (zAxis.x * xAxis.z);
yAxis.z = (zAxis.x * xAxis.y) - (zAxis.y * xAxis.x);
// -dot(xAxis, position)
result1 = ((xAxis.x * position.x) + (xAxis.y * position.y) + (xAxis.z * position.z)) * -1.0f;
// -dot(yaxis, position)
result2 = ((yAxis.x * position.x) + (yAxis.y * position.y) + (yAxis.z * position.z)) * -1.0f;
// -dot(zaxis, position)
result3 = ((zAxis.x * position.x) + (zAxis.y * position.y) + (zAxis.z * position.z)) * -1.0f;
// Set the computed values in the view matrix.
m_viewMatrix[0] = xAxis.x;
m_viewMatrix[1] = yAxis.x;
m_viewMatrix[2] = zAxis.x;
m_viewMatrix[3] = 0.0f;
m_viewMatrix[4] = xAxis.y;
m_viewMatrix[5] = yAxis.y;
m_viewMatrix[6] = zAxis.y;
m_viewMatrix[7] = 0.0f;
m_viewMatrix[8] = xAxis.z;
m_viewMatrix[9] = yAxis.z;
m_viewMatrix[10] = zAxis.z;
m_viewMatrix[11] = 0.0f;
m_viewMatrix[12] = result1;
m_viewMatrix[13] = result2;
m_viewMatrix[14] = result3;
m_viewMatrix[15] = 1.0f;
return;
}
void LightClass::GenerateProjectionMatrix(float screenDepth, float screenNear)
{
float fieldOfView, screenAspect;
// Setup field of view and screen aspect for a square light source.
fieldOfView = 3.14159265358979323846f / 2.0f;
screenAspect = 1.0f;
// Create the projection matrix for the view point.
BuildMatrixPerspectiveFovLH(fieldOfView, screenAspect, screenNear, screenDepth);
return;
}
void LightClass::BuildMatrixPerspectiveFovLH(float fieldOfView, float screenAspect, float screenNear, float screenDepth)
{
m_projectionMatrix[0] = 1.0f / (screenAspect * tan(fieldOfView * 0.5f));
m_projectionMatrix[1] = 0.0f;
m_projectionMatrix[2] = 0.0f;
m_projectionMatrix[3] = 0.0f;
m_projectionMatrix[4] = 0.0f;
m_projectionMatrix[5] = 1.0f / tan(fieldOfView * 0.5f);
m_projectionMatrix[6] = 0.0f;
m_projectionMatrix[7] = 0.0f;
m_projectionMatrix[8] = 0.0f;
m_projectionMatrix[9] = 0.0f;
m_projectionMatrix[10] = screenDepth / (screenDepth - screenNear);
m_projectionMatrix[11] = 1.0f;
m_projectionMatrix[12] = 0.0f;
m_projectionMatrix[13] = 0.0f;
m_projectionMatrix[14] = (-screenNear * screenDepth) / (screenDepth - screenNear);
m_projectionMatrix[15] = 0.0f;
return;
}
We have added code to generate an orthographic projection matrix.
This will create a square projection matrix to simulate how directional light would illuminate an area.
void LightClass::GenerateOrthoMatrix(float width, float nearPlane, float farPlane)
{
m_orthoMatrix[0] = 2.0f / width;
m_orthoMatrix[1] = 0.0f;
m_orthoMatrix[2] = 0.0f;
m_orthoMatrix[3] = 0.0f;
m_orthoMatrix[4] = 0.0f;
m_orthoMatrix[5] = 2.0f / width;
m_orthoMatrix[6] = 0.0f;
m_orthoMatrix[7] = 0.0f;
m_orthoMatrix[8] = 0.0f;
m_orthoMatrix[9] = 0.0f;
m_orthoMatrix[10] = 1.0f / (farPlane - nearPlane);
m_orthoMatrix[11] = 0.0f;
m_orthoMatrix[12] = 0.0f;
m_orthoMatrix[13] = 0.0f;
m_orthoMatrix[14] = nearPlane / (nearPlane - farPlane);
m_orthoMatrix[15] = 1.0f;
return;
}
void LightClass::GetViewMatrix(float* matrix)
{
matrix[0] = m_viewMatrix[0];
matrix[1] = m_viewMatrix[1];
matrix[2] = m_viewMatrix[2];
matrix[3] = m_viewMatrix[3];
matrix[4] = m_viewMatrix[4];
matrix[5] = m_viewMatrix[5];
matrix[6] = m_viewMatrix[6];
matrix[7] = m_viewMatrix[7];
matrix[8] = m_viewMatrix[8];
matrix[9] = m_viewMatrix[9];
matrix[10] = m_viewMatrix[10];
matrix[11] = m_viewMatrix[11];
matrix[12] = m_viewMatrix[12];
matrix[13] = m_viewMatrix[13];
matrix[14] = m_viewMatrix[14];
matrix[15] = m_viewMatrix[15];
return;
}
void LightClass::GetProjectionMatrix(float* matrix)
{
matrix[0] = m_projectionMatrix[0];
matrix[1] = m_projectionMatrix[1];
matrix[2] = m_projectionMatrix[2];
matrix[3] = m_projectionMatrix[3];
matrix[4] = m_projectionMatrix[4];
matrix[5] = m_projectionMatrix[5];
matrix[6] = m_projectionMatrix[6];
matrix[7] = m_projectionMatrix[7];
matrix[8] = m_projectionMatrix[8];
matrix[9] = m_projectionMatrix[9];
matrix[10] = m_projectionMatrix[10];
matrix[11] = m_projectionMatrix[11];
matrix[12] = m_projectionMatrix[12];
matrix[13] = m_projectionMatrix[13];
matrix[14] = m_projectionMatrix[14];
matrix[15] = m_projectionMatrix[15];
return;
}
void LightClass::GetOrthoMatrix(float* matrix)
{
matrix[0] = m_orthoMatrix[0];
matrix[1] = m_orthoMatrix[1];
matrix[2] = m_orthoMatrix[2];
matrix[3] = m_orthoMatrix[3];
matrix[4] = m_orthoMatrix[4];
matrix[5] = m_orthoMatrix[5];
matrix[6] = m_orthoMatrix[6];
matrix[7] = m_orthoMatrix[7];
matrix[8] = m_orthoMatrix[8];
matrix[9] = m_orthoMatrix[9];
matrix[10] = m_orthoMatrix[10];
matrix[11] = m_orthoMatrix[11];
matrix[12] = m_orthoMatrix[12];
matrix[13] = m_orthoMatrix[13];
matrix[14] = m_orthoMatrix[14];
matrix[15] = m_orthoMatrix[15];
return;
}
Applicationclass.h
////////////////////////////////////////////////////////////////////////////////
// Filename: applicationclass.h
////////////////////////////////////////////////////////////////////////////////
#ifndef _APPLICATIONCLASS_H_
#define _APPLICATIONCLASS_H_
/////////////
// GLOBALS //
/////////////
const bool FULL_SCREEN = false;
const bool VSYNC_ENABLED = true;
const float SCREEN_NEAR = 1.0f;
const float SCREEN_DEPTH = 100.0f;
const int SHADOWMAP_WIDTH = 1024;
const int SHADOWMAP_HEIGHT = 1024;
Two new globals were added to give individual control over the depth range of the shadow map.
const float SHADOWMAP_DEPTH = 50.0f;
const float SHADOWMAP_NEAR = 1.0f;
///////////////////////
// MY CLASS INCLUDES //
///////////////////////
#include "inputclass.h"
#include "openglclass.h"
#include "cameraclass.h"
#include "modelclass.h"
#include "lightclass.h"
#include "rendertextureclass.h"
#include "depthshaderclass.h"
#include "shadowshaderclass.h"
////////////////////////////////////////////////////////////////////////////////
// Class Name: ApplicationClass
////////////////////////////////////////////////////////////////////////////////
class ApplicationClass
{
public:
ApplicationClass();
ApplicationClass(const ApplicationClass&);
~ApplicationClass();
bool Initialize(Display*, Window, int, int);
void Shutdown();
bool Frame(InputClass*);
private:
bool RenderDepthToTexture();
bool Render();
private:
OpenGLClass* m_OpenGL;
CameraClass* m_Camera;
ModelClass *m_CubeModel, *m_SphereModel, *m_GroundModel;
LightClass* m_Light;
RenderTextureClass* m_RenderTexture;
DepthShaderClass* m_DepthShader;
ShadowShaderClass* m_ShadowShader;
float m_shadowMapBias;
};
#endif
Applicationclass.cpp
////////////////////////////////////////////////////////////////////////////////
// Filename: applicationclass.cpp
////////////////////////////////////////////////////////////////////////////////
#include "applicationclass.h"
ApplicationClass::ApplicationClass()
{
m_OpenGL = 0;
m_Camera = 0;
m_CubeModel = 0;
m_SphereModel = 0;
m_GroundModel = 0;
m_Light = 0;
m_RenderTexture = 0;
m_DepthShader = 0;
m_ShadowShader = 0;
}
ApplicationClass::ApplicationClass(const ApplicationClass& other)
{
}
ApplicationClass::~ApplicationClass()
{
}
bool ApplicationClass::Initialize(Display* display, Window win, int screenWidth, int screenHeight)
{
char modelFilename[128], textureFilename[128];
bool result;
// Create and initialize the OpenGL object.
m_OpenGL = new OpenGLClass;
result = m_OpenGL->Initialize(display, win, screenWidth, screenHeight, SCREEN_NEAR, SCREEN_DEPTH, VSYNC_ENABLED);
if(!result)
{
cout << "Error: Could not initialize the OpenGL object." << endl;
return false;
}
// Create and initialize the camera object.
m_Camera = new CameraClass;
// Position camera to view scene from behind to see the shadow effect better.
m_Camera->SetPosition(0.0f, 7.0f, -10.0f);
m_Camera->SetRotation(35.0f, 0.0f, 0.0f);
m_Camera->Render();
// Create and initialize the cube model object.
m_CubeModel = new ModelClass;
strcpy(modelFilename, "../Engine/data/cube.txt");
strcpy(textureFilename, "../Engine/data/wall01.tga");
result = m_CubeModel->Initialize(m_OpenGL, modelFilename, textureFilename, false, NULL, false, NULL, false);
if(!result)
{
cout << "Error: Could not initialize the cube model object." << endl;
return false;
}
// Create and initialize the sphere model object.
m_SphereModel = new ModelClass;
strcpy(modelFilename, "../Engine/data/sphere.txt");
strcpy(textureFilename, "../Engine/data/ice.tga");
result = m_SphereModel->Initialize(m_OpenGL, modelFilename, textureFilename, true, NULL, false, NULL, false);
if(!result)
{
cout << "Error: Could not initialize the sphere model object." << endl;
return false;
}
// Create and initialize the ground model object.
m_GroundModel = new ModelClass;
strcpy(modelFilename, "../Engine/data/plane01.txt");
strcpy(textureFilename, "../Engine/data/metal001.tga");
result = m_GroundModel->Initialize(m_OpenGL, modelFilename, textureFilename, false, NULL, false, NULL, false);
if(!result)
{
cout << "Error: Could not initialize the ground model object." << endl;
return false;
}
// Create and initialize the light object.
m_Light = new LightClass;
m_Light->SetAmbientLight(0.15f, 0.15f, 0.15f, 1.0f);
m_Light->SetDiffuseColor(1.0f, 1.0f, 1.0f, 1.0f);
An orthographic matrix is now generated for the directional light instead of the positional projection matrix.
m_Light->GenerateOrthoMatrix(20.0f, SHADOWMAP_NEAR, SHADOWMAP_DEPTH);
// Create and initialize the render to texture object.
m_RenderTexture = new RenderTextureClass;
The shadow map is initialized with the two new globals that control the depth range.
result = m_RenderTexture->Initialize(m_OpenGL, SHADOWMAP_WIDTH, SHADOWMAP_HEIGHT, SHADOWMAP_NEAR, SHADOWMAP_DEPTH, 0);
if(!result)
{
cout << "Error: Could not initialize the render texture object." << endl;
return false;
}
// Create and initialize the depth shader object.
m_DepthShader = new DepthShaderClass;
result = m_DepthShader->Initialize(m_OpenGL);
if(!result)
{
cout << "Error: Could not initialize the depth shader object." << endl;
return false;
}
// Create and initialize the shadow shader object.
m_ShadowShader = new ShadowShaderClass;
result = m_ShadowShader->Initialize(m_OpenGL);
if(!result)
{
cout << "Error: Could not initialize the shadow shader object." << endl;
return false;
}
// Set the shadow map bias to fix the floating point precision issues (shadow acne/lines artifacts).
m_shadowMapBias = 0.0022f;
return true;
}
void ApplicationClass::Shutdown()
{
// Release the shadow shader object.
if(m_ShadowShader)
{
m_ShadowShader->Shutdown();
delete m_ShadowShader;
m_ShadowShader = 0;
}
// Release the depth shader object.
if(m_DepthShader)
{
m_DepthShader->Shutdown();
delete m_DepthShader;
m_DepthShader = 0;
}
// Release the render texture object.
if(m_RenderTexture)
{
m_RenderTexture->Shutdown();
delete m_RenderTexture;
m_RenderTexture = 0;
}
// Release the light object.
if(m_Light)
{
delete m_Light;
m_Light = 0;
}
// Release the ground model object.
if(m_GroundModel)
{
m_GroundModel->Shutdown();
delete m_GroundModel;
m_GroundModel = 0;
}
// Release the sphere model object.
if(m_SphereModel)
{
m_SphereModel->Shutdown();
delete m_SphereModel;
m_SphereModel = 0;
}
// Release the cube model object.
if(m_CubeModel)
{
m_CubeModel->Shutdown();
delete m_CubeModel;
m_CubeModel = 0;
}
// Release the camera object.
if(m_Camera)
{
delete m_Camera;
m_Camera = 0;
}
// Release the OpenGL object.
if(m_OpenGL)
{
m_OpenGL->Shutdown();
delete m_OpenGL;
m_OpenGL = 0;
}
return;
}
bool ApplicationClass::Frame(InputClass* Input)
{
static float lightAngle = 270.0f;
static float lightPosX = 9.0f;
float radians;
float frameTime;
bool result;
// Check if the escape key has been pressed, if so quit.
if(Input->IsEscapePressed() == true)
{
return false;
}
Each frame we now rotate a directional light from 270 degrees to 90 degrees to simulate sun light movement.
// Set the frame time manually assumming 60 fps.
frameTime = 10.0f;
// Update the position of the light each frame.
lightPosX -= 0.003f * frameTime;
// Update the angle of the light each frame.
lightAngle -= 0.03f * frameTime;
if(lightAngle < 90.0f)
{
lightAngle = 270.0f;
// Reset the light position also.
lightPosX = 9.0f;
}
radians = lightAngle * 0.0174532925f;
// Update the direction of the light.
m_Light->SetDirection(sinf(radians), cosf(radians), 0.0f);
Also, each frame we now simulate a sun light rotation using the position and lookat.
As a directional light has no position, we have to just create a simulated version of it by polarizing the position and lookat X coordinate.
If your light needs to cover more distance then just increase the Y coordinate distance between the position and the lookat.
// Set the position and lookat for the light.
m_Light->SetPosition(lightPosX, 8.0f, -0.1f);
m_Light->SetLookAt(-lightPosX, 0.0f, 0.0f);
m_Light->GenerateViewMatrix();
// Render the scene depth for the first light to it's render texture.
result = RenderDepthToTexture();
if(!result)
{
return false;
}
// Render the final graphics scene.
result = Render();
if(!result)
{
return false;
}
return true;
}
In the RenderDepthToTexture function we now change everything from a projection matrix to an orthographic matrix.
bool ApplicationClass::RenderDepthToTexture()
{
float translateMatrix[16], lightViewMatrix[16], lightOrthoMatrix[16];
bool result;
// Set the render target to be the render texture and clear it.
m_RenderTexture->SetRenderTarget();
m_RenderTexture->ClearRenderTarget(0.0f, 0.0f, 0.0f, 1.0f);
// Get the view and orthographic matrices from the light object.
m_Light->GetViewMatrix(lightViewMatrix);
m_Light->GetOrthoMatrix(lightOrthoMatrix);
// Setup the translation matrix for the cube model.
m_OpenGL->MatrixTranslation(translateMatrix, -2.0f, 2.0f, 0.0f);
// Render the cube model using the depth shader and the light matrices.
result = m_DepthShader->SetShaderParameters(translateMatrix, lightViewMatrix, lightOrthoMatrix);
if(!result)
{
return false;
}
m_CubeModel->Render();
// Setup the translation matrix for the sphere model.
m_OpenGL->MatrixTranslation(translateMatrix, 2.0f, 2.0f, 0.0f);
// Render the sphere model using the depth shader and the light matrices.
result = m_DepthShader->SetShaderParameters(translateMatrix, lightViewMatrix, lightOrthoMatrix);
if(!result)
{
return false;
}
m_SphereModel->Render();
// Setup the translation matrix for the ground model.
m_OpenGL->MatrixTranslation(translateMatrix, 0.0f, 1.0f, 0.0f);
// Render the ground model using the depth shader and the light matrices.
result = m_DepthShader->SetShaderParameters(translateMatrix, lightViewMatrix, lightOrthoMatrix);
if(!result)
{
return false;
}
m_GroundModel->Render();
// Reset the render target back to the original back buffer and not the render to texture anymore. And reset the viewport back to the original.
m_OpenGL->SetBackBufferRenderTarget();
m_OpenGL->ResetViewport();
return true;
}
In the Render function we also change everything to use an orthographic matrix instead of a projection matrix.
The shader render functions also now take the light direction as opposed to previously using the light position.
bool ApplicationClass::Render()
{
float worldMatrix[16], viewMatrix[16], projectionMatrix[16], lightViewMatrix[16], lightOrthoMatrix[16];
float diffuseColor[4], ambientColor[4], lightDirection[3];
bool result;
// Clear the buffers to begin the scene.
m_OpenGL->BeginScene(0.0f, 0.0f, 0.0f, 1.0f);
// Get the world, view, and projection matrices from the opengl and camera objects.
m_OpenGL->GetWorldMatrix(worldMatrix);
m_Camera->GetViewMatrix(viewMatrix);
m_OpenGL->GetProjectionMatrix(projectionMatrix);
// Get the light view and projection matrices.
m_Light->GetViewMatrix(lightViewMatrix);
m_Light->GetOrthoMatrix(lightOrthoMatrix);
// Get the light properties.
m_Light->GetDiffuseColor(diffuseColor);
m_Light->GetAmbientLight(ambientColor);
m_Light->GetDirection(lightDirection);
// Setup the translation matrix for the cube model.
m_OpenGL->MatrixTranslation(worldMatrix, -2.0f, 2.0f, 0.0f);
// Set the shadow shader as the current shader program and set the parameters that it will use for rendering.
result = m_ShadowShader->SetShaderParameters(worldMatrix, viewMatrix, projectionMatrix, lightViewMatrix, lightOrthoMatrix,
diffuseColor, ambientColor, lightDirection, m_shadowMapBias);
if(!result)
{
return false;
}
// Set the render texture in texture unit 1.
m_RenderTexture->SetTexture(1);
// Render the cube model using the shadow shader.
m_CubeModel->SetTexture1(0);
m_CubeModel->Render();
// Setup the translation matrix for the sphere model.
m_OpenGL->MatrixTranslation(worldMatrix, 2.0f, 2.0f, 0.0f);
// Set the shadow shader as the current shader program and set the parameters that it will use for rendering.
result = m_ShadowShader->SetShaderParameters(worldMatrix, viewMatrix, projectionMatrix, lightViewMatrix, lightOrthoMatrix,
diffuseColor, ambientColor, lightDirection, m_shadowMapBias);
if(!result)
{
return false;
}
// Set the render texture in texture unit 1.
m_RenderTexture->SetTexture(1);
// Render the sphere model using the shadow shader.
m_SphereModel->SetTexture1(0);
m_SphereModel->Render();
// Setup the translation matrix for the ground model.
m_OpenGL->MatrixTranslation(worldMatrix, 0.0f, 1.0f, 0.0f);
// Set the shadow shader as the current shader program and set the parameters that it will use for rendering.
result = m_ShadowShader->SetShaderParameters(worldMatrix, viewMatrix, projectionMatrix, lightViewMatrix, lightOrthoMatrix,
diffuseColor, ambientColor, lightDirection, m_shadowMapBias);
if(!result)
{
return false;
}
// Set the render texture in texture unit 1.
m_RenderTexture->SetTexture(1);
// Render the ground model using the shadow shader.
m_GroundModel->SetTexture1(0);
m_GroundModel->Render();
// Present the rendered scene to the screen.
m_OpenGL->EndScene();
return true;
}
Summary
Directional shadow maps can now be produced by using directional light and orthographic projections.
To Do Exercises
1. Recompile and run the code.
2. Modify the direction, position, and lookat in the Frame function to see the effect.
Source Code
Source Code and Data Files: gl4linuxtut43_src.tar.gz
