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TextureWrap.c
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TextureWrap.c
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// The MIT License (MIT)
//
// Copyright (c) 2013 Dan Ginsburg, Budirijanto Purnomo
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// Book: OpenGL(R) ES 3.0 Programming Guide, 2nd Edition
// Authors: Dan Ginsburg, Budirijanto Purnomo, Dave Shreiner, Aaftab Munshi
// ISBN-10: 0-321-93388-5
// ISBN-13: 978-0-321-93388-1
// Publisher: Addison-Wesley Professional
// URLs: http://www.opengles-book.com
// http://my.safaribooksonline.com/book/animation-and-3d/9780133440133
//
// TextureWrap.c
//
// This is an example that demonstrates the three texture
// wrap modes available on 2D textures
//
#include <stdlib.h>
#include "esUtil.h"
typedef struct
{
// Handle to a program object
GLuint programObject;
// Sampler location
GLint samplerLoc;
// Offset location
GLint offsetLoc;
// Texture handle
GLuint textureId;
} UserData;
///
// Generate an RGB8 checkerboard image
//
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 * width + x ) * 3] = rColor;
pixels[ ( y * width + x ) * 3 + 1] = 0;
pixels[ ( y * width + x ) * 3 + 2] = bColor;
}
return pixels;
}
///
// Create a mipmapped 2D texture image
//
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 Init ( ESContext *esContext )
{
UserData *userData = esContext->userData;
char vShaderStr[] =
"#version 300 es \n"
"uniform float u_offset; \n"
"layout(location = 0) in vec4 a_position; \n"
"layout(location = 1) in vec2 a_texCoord; \n"
"out 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";
char fShaderStr[] =
"#version 300 es \n"
"precision mediump float; \n"
"in vec2 v_texCoord; \n"
"layout(location = 0) out vec4 outColor; \n"
"uniform sampler2D s_texture; \n"
"void main() \n"
"{ \n"
" outColor = texture( s_texture, v_texCoord ); \n"
"} \n";
// Load the shaders and get a linked program object
userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
// 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 ();
glClearColor ( 1.0f, 1.0f, 1.0f, 0.0f );
return TRUE;
}
///
// Draw a triangle using the shader pair created in Init()
//
void Draw ( ESContext *esContext )
{
UserData *userData = esContext->userData;
GLfloat vVertices[] = { -0.3f, 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 };
// 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 ( 0, 4, GL_FLOAT,
GL_FALSE, 6 * sizeof ( GLfloat ), vVertices );
// Load the texture coordinate
glVertexAttribPointer ( 1, 2, GL_FLOAT,
GL_FALSE, 6 * sizeof ( GLfloat ), &vVertices[4] );
glEnableVertexAttribArray ( 0 );
glEnableVertexAttribArray ( 1 );
// 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, indices );
// 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, indices );
// 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, indices );
}
///
// Cleanup
//
void ShutDown ( ESContext *esContext )
{
UserData *userData = esContext->userData;
// Delete texture object
glDeleteTextures ( 1, &userData->textureId );
// Delete program object
glDeleteProgram ( userData->programObject );
}
int esMain ( ESContext *esContext )
{
esContext->userData = malloc ( sizeof ( UserData ) );
esCreateWindow ( esContext, "TextureWrap", 640, 480, ES_WINDOW_RGB );
if ( !Init ( esContext ) )
{
return GL_FALSE;
}
esRegisterDrawFunc ( esContext, Draw );
esRegisterShutdownFunc ( esContext, ShutDown );
return GL_TRUE;
}