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//
// 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
//
// MultiTexture.c
//
// This is an example that draws a quad with a basemap and
// lightmap to demonstrate multitexturing.
//
#include <stdlib.h>
#include "esUtil.h"
typedef struct
{
// Handle to a program object
GLuint programObject;
// Attribute locations
GLint positionLoc;
GLint texCoordLoc;
// Sampler locations
GLint baseMapLoc;
GLint lightMapLoc;
// Texture handle
GLuint baseMapTexId;
GLuint lightMapTexId;
} UserData;
///
// Load texture from disk
//
GLuint LoadTexture ( char *fileName )
{
int width,
height;
char *buffer = esLoadTGA ( fileName, &width, &height );
GLuint texId;
if ( buffer == NULL )
{
esLogMessage ( "Error loading (%s) image.\n", fileName );
return 0;
}
glGenTextures ( 1, &texId );
glBindTexture ( GL_TEXTURE_2D, texId );
glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, buffer );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
free ( buffer );
return texId;
}
///
// Initialize the shader and program object
//
int Init ( ESContext *esContext )
{
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 fShaderStr[] =
"precision mediump float; \n"
"varying vec2 v_texCoord; \n"
"uniform sampler2D s_baseMap; \n"
"uniform sampler2D s_lightMap; \n"
"void main() \n"
"{ \n"
" vec4 baseColor; \n"
" vec4 lightColor; \n"
" \n"
" baseColor = texture2D( s_baseMap, v_texCoord ); \n"
" lightColor = texture2D( s_lightMap, v_texCoord ); \n"
" gl_FragColor = baseColor * (lightColor + 0.25); \n"
"} \n";
// Load the shaders and get a linked program object
userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
// Get the attribute locations
userData->positionLoc = glGetAttribLocation ( userData->programObject, "a_position" );
userData->texCoordLoc = glGetAttribLocation ( userData->programObject, "a_texCoord" );
// Get the sampler location
userData->baseMapLoc = glGetUniformLocation ( userData->programObject, "s_baseMap" );
userData->lightMapLoc = glGetUniformLocation ( userData->programObject, "s_lightMap" );
// Load the textures
userData->baseMapTexId = LoadTexture ( "basemap.tga" );
userData->lightMapTexId = LoadTexture ( "lightmap.tga" );
if ( userData->baseMapTexId == 0 || userData->lightMapTexId == 0 )
return FALSE;
glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
return TRUE;
}
///
// Draw a triangle using the shader pair created in Init()
//
void Draw ( ESContext *esContext )
{
UserData *userData = esContext->userData;
GLfloat vVertices[] = { -0.5f, 0.5f, 0.0f, // Position 0
0.0f, 0.0f, // TexCoord 0
-0.5f, -0.5f, 0.0f, // Position 1
0.0f, 1.0f, // TexCoord 1
0.5f, -0.5f, 0.0f, // Position 2
1.0f, 1.0f, // TexCoord 2
0.5f, 0.5f, 0.0f, // Position 3
1.0f, 0.0f // TexCoord 3
};
GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
// 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->programObject );
// 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 base map
glActiveTexture ( GL_TEXTURE0 );
glBindTexture ( GL_TEXTURE_2D, userData->baseMapTexId );
// Set the base map sampler to texture unit to 0
glUniform1i ( userData->baseMapLoc, 0 );
// Bind the light map
glActiveTexture ( GL_TEXTURE1 );
glBindTexture ( GL_TEXTURE_2D, userData->lightMapTexId );
// Set the light map sampler to texture unit 1
glUniform1i ( userData->lightMapLoc, 1 );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, indices );
eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
}
///
// Cleanup
//
void ShutDown ( ESContext *esContext )
{
UserData *userData = esContext->userData;
// Delete texture object
glDeleteTextures ( 1, &userData->baseMapTexId );
glDeleteTextures ( 1, &userData->lightMapTexId );
// Delete program object
glDeleteProgram ( userData->programObject );
}
int main ( int argc, char *argv[] )
{
ESContext esContext;
UserData userData;
esInitContext ( &esContext );
esContext.userData = &userData;
esCreateWindow ( &esContext, TEXT("MultiTexture"), 320, 240, ES_WINDOW_RGB );
if ( !Init ( &esContext ) )
return 0;
esRegisterDrawFunc ( &esContext, Draw );
esMainLoop ( &esContext );
ShutDown ( &esContext );
}
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