| // |
| // 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 |
| // |
| |
| // Hello_Triangle.c |
| // |
| // This is a simple example that draws a single triangle with |
| // a minimal vertex/fragment shader. The purpose of this |
| // example is to demonstrate the basic concepts of |
| // OpenGL ES 2.0 rendering. |
| #include <stdlib.h> |
| #include "esUtil.h" |
| |
| typedef struct |
| { |
| // Handle to a program object |
| GLuint programObject; |
| |
| } UserData; |
| |
| /// |
| // Create a shader object, load the shader source, and |
| // compile the shader. |
| // |
| GLuint LoadShader ( GLenum type, const char *shaderSrc ) |
| { |
| GLuint shader; |
| GLint compiled; |
| |
| // Create the shader object |
| shader = glCreateShader ( type ); |
| |
| if ( shader == 0 ) |
| return 0; |
| |
| // Load the shader source |
| glShaderSource ( shader, 1, &shaderSrc, NULL ); |
| |
| // Compile the shader |
| glCompileShader ( shader ); |
| |
| // Check the compile status |
| glGetShaderiv ( shader, GL_COMPILE_STATUS, &compiled ); |
| |
| if ( !compiled ) |
| { |
| GLint infoLen = 0; |
| |
| glGetShaderiv ( shader, GL_INFO_LOG_LENGTH, &infoLen ); |
| |
| if ( infoLen > 1 ) |
| { |
| char* infoLog = malloc (sizeof(char) * infoLen ); |
| |
| glGetShaderInfoLog ( shader, infoLen, NULL, infoLog ); |
| esLogMessage ( "Error compiling shader:\n%s\n", infoLog ); |
| |
| free ( infoLog ); |
| } |
| |
| glDeleteShader ( shader ); |
| return 0; |
| } |
| |
| return shader; |
| |
| } |
| |
| /// |
| // Initialize the shader and program object |
| // |
| int Init ( ESContext *esContext ) |
| { |
| UserData *userData = esContext->userData; |
| GLbyte vShaderStr[] = |
| "attribute vec4 vPosition; \n" |
| "void main() \n" |
| "{ \n" |
| " gl_Position = vPosition; \n" |
| "} \n"; |
| |
| GLbyte fShaderStr[] = |
| "precision mediump float;\n"\ |
| "void main() \n" |
| "{ \n" |
| " gl_FragColor = vec4 ( 1.0, 0.0, 0.0, 1.0 );\n" |
| "} \n"; |
| |
| GLuint vertexShader; |
| GLuint fragmentShader; |
| GLuint programObject; |
| GLint linked; |
| |
| // Load the vertex/fragment shaders |
| vertexShader = LoadShader ( GL_VERTEX_SHADER, vShaderStr ); |
| fragmentShader = LoadShader ( GL_FRAGMENT_SHADER, fShaderStr ); |
| |
| // Create the program object |
| programObject = glCreateProgram ( ); |
| |
| if ( programObject == 0 ) |
| return 0; |
| |
| glAttachShader ( programObject, vertexShader ); |
| glAttachShader ( programObject, fragmentShader ); |
| |
| // Bind vPosition to attribute 0 |
| glBindAttribLocation ( programObject, 0, "vPosition" ); |
| |
| // Link the program |
| glLinkProgram ( programObject ); |
| |
| // Check the link status |
| glGetProgramiv ( programObject, GL_LINK_STATUS, &linked ); |
| |
| if ( !linked ) |
| { |
| GLint infoLen = 0; |
| |
| glGetProgramiv ( programObject, GL_INFO_LOG_LENGTH, &infoLen ); |
| |
| if ( infoLen > 1 ) |
| { |
| char* infoLog = malloc (sizeof(char) * infoLen ); |
| |
| glGetProgramInfoLog ( programObject, infoLen, NULL, infoLog ); |
| esLogMessage ( "Error linking program:\n%s\n", infoLog ); |
| |
| free ( infoLog ); |
| } |
| |
| glDeleteProgram ( programObject ); |
| return FALSE; |
| } |
| |
| // Store the program object |
| userData->programObject = programObject; |
| |
| 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[] = { 0.0f, 0.5f, 0.0f, |
| -0.5f, -0.5f, 0.0f, |
| 0.5f, -0.5f, 0.0f }; |
| |
| // 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 data |
| glVertexAttribPointer ( 0, 3, GL_FLOAT, GL_FALSE, 0, vVertices ); |
| glEnableVertexAttribArray ( 0 ); |
| |
| glDrawArrays ( GL_TRIANGLES, 0, 3 ); |
| |
| eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface ); |
| } |
| |
| |
| int main ( int argc, char *argv[] ) |
| { |
| ESContext esContext; |
| UserData userData; |
| |
| esInitContext ( &esContext ); |
| esContext.userData = &userData; |
| |
| esCreateWindow ( &esContext, TEXT("Hello Triangle"), 320, 240, ES_WINDOW_RGB ); |
| |
| if ( !Init ( &esContext ) ) |
| return 0; |
| |
| esRegisterDrawFunc ( &esContext, Draw ); |
| |
| esMainLoop ( &esContext ); |
| } |