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//
// Modified from Simple_Texture2D, found in:
//
// Book: OpenGL(R) ES 2.0 Programming Guide
// Authors: Aaftab Munshi, Dan Ginsburg, Dave Shreiner
// ISBN-10: 0321502795
// ISBN-13: 9780321502797
// Publisher: Addison-Wesley Professional
// URLs: http://safari.informit.com/9780321563835
// http://www.opengles-book.com
//
// MultipleRenderTargets.c
//
// This is a simple example that shows how to use multiple render
// targets in GLES 2.0 using EXT_draw_buffers. The example
// draws to three render targets and displays
// them together in a final pass.
//
#include <stdlib.h>
#include "esUtil.h"
PFNGLDRAWBUFFERSEXTPROC glDrawBuffersEXT;
typedef struct
{
// Handle to a program object
GLuint programObjectMRT;
GLuint programObject;
// Attribute locations
GLint positionLoc;
GLint texCoordLoc;
// Sampler location
GLint samplerLoc;
// Texture handle
GLuint textureId;
// Framebuffer object handle
GLuint framebuffer;
// Framebuffer color attachments
GLuint framebufferTextures[4];
} UserData;
///
// Create a simple 2x2 texture image with four different colors
//
GLuint CreateSimpleTexture2D( )
{
// Texture object handle
GLuint textureId;
// 2x2 Image, 3 bytes per pixel (R, G, B)
GLubyte pixels[4 * 3] =
{
255, 0, 0, // Red
0, 255, 0, // Green
0, 0, 255, // Blue
255, 255, 0 // Yellow
};
// Use tightly packed data
glPixelStorei ( GL_UNPACK_ALIGNMENT, 1 );
// Generate a texture object
glGenTextures ( 1, &textureId );
// Bind the texture object
glBindTexture ( GL_TEXTURE_2D, textureId );
// Load the texture
glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0, GL_RGB, GL_UNSIGNED_BYTE, pixels );
// Set the filtering mode
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
return textureId;
}
///
// Initialize the shader and program object
//
int Init ( ESContext *esContext )
{
UserData *userData = (UserData*)esContext->userData;
GLbyte vShaderStr[] =
"attribute vec4 a_position; \n"
"attribute vec2 a_texCoord; \n"
"varying vec2 v_texCoord; \n"
"void main() \n"
"{ \n"
" gl_Position = a_position; \n"
" v_texCoord = a_texCoord; \n"
"} \n";
GLbyte fMultiShaderStr[] =
"#extension GL_EXT_draw_buffers : enable \n"
"precision mediump float; \n"
"varying vec2 v_texCoord; \n"
"uniform sampler2D s_texture; \n"
"void main() \n"
"{ \n"
" vec4 color = texture2D( s_texture, v_texCoord ); \n"
" gl_FragData[0] = color; \n"
" gl_FragData[1] = vec4(1.0, 1.0, 1.0, 1.0) - color.brga;\n"
" gl_FragData[2] = vec4(0.2, 1.0, 0.5, 1.0) * color.gbra;\n"
" gl_FragData[3] = color.rrra; \n"
"} \n";
GLbyte fShaderStr[] =
"precision mediump float; \n"
"varying vec2 v_texCoord; \n"
"uniform sampler2D s_texture; \n"
"void main() \n"
"{ \n"
" vec4 color = texture2D( s_texture, v_texCoord ); \n"
" gl_FragColor = color; \n"
"} \n";
int i;
// Check EXT_draw_buffers is supported
if (strstr(glGetString(GL_EXTENSIONS), "GL_EXT_draw_buffers") == 0)
{
return FALSE;
}
// Retrieve the address of glDrawBuffersEXT from EGL
glDrawBuffersEXT = (PFNGLDRAWBUFFERSEXTPROC)eglGetProcAddress("glDrawBuffersEXT");
// Load the shaders and get a linked program object
userData->programObject = esLoadProgram ( (const char*)vShaderStr, (const char*)fShaderStr );
userData->programObjectMRT = esLoadProgram ( (const char*)vShaderStr, (const char*)fMultiShaderStr );
// Get the attribute locations
userData->positionLoc = glGetAttribLocation ( userData->programObject, "a_position" );
userData->texCoordLoc = glGetAttribLocation ( userData->programObject, "a_texCoord" );
// Get the sampler location
userData->samplerLoc = glGetUniformLocation ( userData->programObject, "s_texture" );
// Load the texture
userData->textureId = CreateSimpleTexture2D ();
glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
// Initialize the user framebuffer
glGenFramebuffers(1, &userData->framebuffer);
glGenTextures(4, userData->framebufferTextures);
glBindFramebuffer(GL_FRAMEBUFFER, userData->framebuffer);
for (i = 0; i < 4; i++)
{
// Create textures for the four color attachments
glBindTexture(GL_TEXTURE_2D, userData->framebufferTextures[i]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, esContext->width, esContext->height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0_EXT + i, GL_TEXTURE_2D, userData->framebufferTextures[i], 0);
}
glBindTexture(GL_TEXTURE_2D, 0);
return TRUE;
}
///
// Draw a triangle using the shader pair created in Init()
//
void Draw ( ESContext *esContext )
{
UserData *userData = (UserData*)esContext->userData;
GLfloat vVertices[] = { -0.8f, 0.8f, 0.0f, // Position 0
0.0f, 0.0f, // TexCoord 0
-0.8f, -0.8f, 0.0f, // Position 1
0.0f, 1.0f, // TexCoord 1
0.8f, -0.8f, 0.0f, // Position 2
1.0f, 1.0f, // TexCoord 2
0.8f, 0.8f, 0.0f, // Position 3
1.0f, 0.0f // TexCoord 3
};
GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
GLenum drawBuffers[] = { GL_COLOR_ATTACHMENT0_EXT, GL_COLOR_ATTACHMENT1_EXT, GL_COLOR_ATTACHMENT2_EXT, GL_COLOR_ATTACHMENT3_EXT };
// Enable drawing to the four color attachments of the user framebuffer
glBindFramebuffer(GL_FRAMEBUFFER, userData->framebuffer);
glDrawBuffersEXT(4, drawBuffers);
// Set the viewport
glViewport ( 0, 0, esContext->width, esContext->height );
// Clear the color buffer
glClear ( GL_COLOR_BUFFER_BIT );
// Use the program object
glUseProgram ( userData->programObjectMRT );
// Load the vertex position
glVertexAttribPointer ( userData->positionLoc, 3, GL_FLOAT,
GL_FALSE, 5 * sizeof(GLfloat), vVertices );
// Load the texture coordinate
glVertexAttribPointer ( userData->texCoordLoc, 2, GL_FLOAT,
GL_FALSE, 5 * sizeof(GLfloat), &vVertices[3] );
glEnableVertexAttribArray ( userData->positionLoc );
glEnableVertexAttribArray ( userData->texCoordLoc );
// Bind the texture
glActiveTexture ( GL_TEXTURE0 );
glBindTexture ( GL_TEXTURE_2D, userData->textureId );
// Set the sampler texture unit to 0
glUniform1i ( userData->samplerLoc, 0 );
// Draw the textured quad to the four render targets
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
// Enable the default framebuffer and single textured drawing
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glUseProgram ( userData->programObject );
// Draw the four textured quads to a separate region in the viewport
glBindTexture( GL_TEXTURE_2D, userData->framebufferTextures[0]);
glViewport ( 0, 0, esContext->width/2, esContext->height/2 );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
glBindTexture( GL_TEXTURE_2D, userData->framebufferTextures[1]);
glViewport ( esContext->width/2, 0, esContext->width/2, esContext->height/2 );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
glBindTexture( GL_TEXTURE_2D, userData->framebufferTextures[2]);
glViewport ( 0, esContext->height/2, esContext->width/2, esContext->height/2 );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
glBindTexture( GL_TEXTURE_2D, userData->framebufferTextures[3]);
glViewport ( esContext->width/2, esContext->height/2, esContext->width/2, esContext->height/2 );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
}
///
// Cleanup
//
void ShutDown ( ESContext *esContext )
{
UserData *userData = (UserData*)esContext->userData;
glDeleteTextures(4, userData->framebufferTextures);
glDeleteFramebuffers(1, &userData->framebuffer);
// Delete texture object
glDeleteTextures ( 1, &userData->textureId );
// Delete program object
glDeleteProgram ( userData->programObject );
eglDestroyContext(esContext->eglDisplay, esContext->eglContext);
eglDestroySurface(esContext->eglDisplay, esContext->eglSurface);
eglTerminate(esContext->eglDisplay);
}
int main ( int argc, char *argv[] )
{
ESContext esContext;
UserData userData;
esInitContext ( &esContext );
esContext.userData = &userData;
esCreateWindow ( &esContext, TEXT("Multiple Render Targets"), 320, 240, ES_WINDOW_RGB );
if ( !Init ( &esContext ) )
return 0;
esRegisterDrawFunc ( &esContext, Draw );
esMainLoop ( &esContext );
ShutDown ( &esContext );
}
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