OpenGL es2.0 第一个例子

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// Hello_Triangle.c

#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 = (char*)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 = (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 ( 0.0, 1.0, 1.0, 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 = (char*) 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 = (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, "Hello Lam Triangle", 320, 240, ES_WINDOW_RGB );

if ( !Init ( &esContext ) )

return 0;

esRegisterDrawFunc ( &esContext, Draw );

esMainLoop ( &esContext );

}

运行结果：

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