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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
//
// TextureWrap.c
//
// This is an example that demonstrates the three texture
// wrap modes available on 2D textures
//
#include <stdlib.h>
#include "TextureWrap.h"
///
// Generate an RGB8 checkerboard image
//
static GLubyte* GenCheckImage( int width, int height, int checkSize )
{
int x,
y;
GLubyte *pixels = malloc( width * height * 3 );
if ( pixels == NULL )
return NULL;
for ( y = 0; y < height; y++ )
for ( x = 0; x < width; x++ )
{
GLubyte rColor = 0;
GLubyte bColor = 0;
if ( ( x / checkSize ) % 2 == 0 )
{
rColor = 255 * ( ( y / checkSize ) % 2 );
bColor = 255 * ( 1 - ( ( y / checkSize ) % 2 ) );
}
else
{
bColor = 255 * ( ( y / checkSize ) % 2 );
rColor = 255 * ( 1 - ( ( y / checkSize ) % 2 ) );
}
pixels[(y * height + x) * 3] = rColor;
pixels[(y * height + x) * 3 + 1] = 0;
pixels[(y * height + x) * 3 + 2] = bColor;
}
return pixels;
}
///
// Create a mipmapped 2D texture image
//
static GLuint CreateTexture2D( )
{
// Texture object handle
GLuint textureId;
int width = 256,
height = 256;
GLubyte *pixels;
pixels = GenCheckImage( width, height, 64 );
if ( pixels == NULL )
return 0;
// Generate a texture object
glGenTextures ( 1, &textureId );
// Bind the texture object
glBindTexture ( GL_TEXTURE_2D, textureId );
// Load mipmap level 0
glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGB, width, height,
0, GL_RGB, GL_UNSIGNED_BYTE, pixels );
// Set the filtering mode
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
return textureId;
}
///
// Initialize the shader and program object
//
int twInit ( ESContext *esContext )
{
TWUserData *userData = esContext->userData;
GLbyte vShaderStr[] =
"uniform float u_offset; \n"
"attribute vec4 a_position; \n"
"attribute vec2 a_texCoord; \n"
"varying vec2 v_texCoord; \n"
"void main() \n"
"{ \n"
" gl_Position = a_position; \n"
" gl_Position.x += u_offset;\n"
" v_texCoord = a_texCoord; \n"
"} \n";
GLbyte fShaderStr[] =
"precision mediump float; \n"
"varying vec2 v_texCoord; \n"
"uniform sampler2D s_texture; \n"
"void main() \n"
"{ \n"
" gl_FragColor = texture2D( s_texture, v_texCoord );\n"
"} \n";
GLfloat vVertices[] = { -0.3f, 0.3f, 0.0f, 1.0f, // Position 0
-1.0f, -1.0f, // TexCoord 0
-0.3f, -0.3f, 0.0f, 1.0f, // Position 1
-1.0f, 2.0f, // TexCoord 1
0.3f, -0.3f, 0.0f, 1.0f, // Position 2
2.0f, 2.0f, // TexCoord 2
0.3f, 0.3f, 0.0f, 1.0f, // Position 3
2.0f, -1.0f // TexCoord 3
};
GLushort indices[] = { 0, 1, 2, 0, 2, 3 };
// 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->samplerLoc = glGetUniformLocation ( userData->programObject, "s_texture" );
// Get the offset location
userData->offsetLoc = glGetUniformLocation( userData->programObject, "u_offset" );
// Load the texture
userData->textureId = CreateTexture2D ();
// Load vertex data
glGenBuffers ( 2, userData->vboIds );
glBindBuffer ( GL_ARRAY_BUFFER, userData->vboIds[0] );
glBufferData ( GL_ARRAY_BUFFER, sizeof(vVertices),
vVertices, GL_STATIC_DRAW );
glBindBuffer ( GL_ELEMENT_ARRAY_BUFFER, userData->vboIds[1] );
glBufferData ( GL_ELEMENT_ARRAY_BUFFER, sizeof(indices),
indices, GL_STATIC_DRAW );
glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
return TRUE;
}
///
// Draw a triangle using the shader pair created in Init()
//
#define VTX_POS_SIZE 4
#define VTX_TEX_SIZE 2
#define VTX_STRIDE (6 * sizeof(GLfloat))
void twDraw ( ESContext *esContext )
{
TWUserData *userData = esContext->userData;
GLuint offset = 0;
// 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, VTX_POS_SIZE, GL_FLOAT,
GL_FALSE, VTX_STRIDE, (GLvoid*) offset );
// Load the texture coordinate
offset += VTX_POS_SIZE * sizeof(GLfloat);
glVertexAttribPointer ( userData->texCoordLoc, VTX_TEX_SIZE, GL_FLOAT,
GL_FALSE, VTX_STRIDE, (GLvoid*) offset );
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 quad with repeat wrap mode
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
glUniform1f ( userData->offsetLoc, -0.7f );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0 );
// Draw quad with clamp to edge wrap mode
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
glUniform1f ( userData->offsetLoc, 0.0f );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0 );
// Draw quad with mirrored repeat
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_MIRRORED_REPEAT );
glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_MIRRORED_REPEAT );
glUniform1f ( userData->offsetLoc, 0.7f );
glDrawElements ( GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0 );
}
///
// Cleanup
//
void twShutDown ( ESContext *esContext )
{
TWUserData *userData = esContext->userData;
// Delete texture object
glDeleteTextures ( 1, &userData->textureId );
// Delete program object
glDeleteProgram ( userData->programObject );
// Delete vertex buffer objects
glDeleteBuffers ( 2, userData->vboIds );
}