| // |
| // 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 "esUtil.h" |
| |
| typedef struct |
| { |
| // Handle to a program object |
| GLuint programObject; |
| |
| // Attribute locations |
| GLint positionLoc; |
| GLint texCoordLoc; |
| |
| // 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 * 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 |
| // |
| 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; |
| 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"; |
| |
| // 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 (); |
| |
| 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[] = { -0.3f, 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 ( userData->positionLoc, 4, GL_FLOAT, |
| GL_FALSE, 6 * sizeof(GLfloat), vVertices ); |
| // Load the texture coordinate |
| glVertexAttribPointer ( userData->texCoordLoc, 2, GL_FLOAT, |
| GL_FALSE, 6 * sizeof(GLfloat), &vVertices[4] ); |
| |
| 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, 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 ); |
| |
| eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface ); |
| } |
| |
| /// |
| // Cleanup |
| // |
| void ShutDown ( ESContext *esContext ) |
| { |
| UserData *userData = esContext->userData; |
| |
| // Delete texture object |
| glDeleteTextures ( 1, &userData->textureId ); |
| |
| // Delete program object |
| glDeleteProgram ( userData->programObject ); |
| } |
| |
| |
| int main ( int argc, char *argv[] ) |
| { |
| ESContext esContext; |
| UserData userData; |
| |
| esInitContext ( &esContext ); |
| esContext.userData = &userData; |
| |
| esCreateWindow ( &esContext, TEXT("Texture Wrap"), 640, 480, ES_WINDOW_RGB ); |
| |
| if ( !Init ( &esContext ) ) |
| return 0; |
| |
| esRegisterDrawFunc ( &esContext, Draw ); |
| |
| esMainLoop ( &esContext ); |
| |
| ShutDown ( &esContext ); |
| } |