OpenGLShader 编程系列-属性变量,一致变量的传递

int Init ( ESContext *esContext )

{

esContext->userData = malloc(sizeof(UserData));

UserData *userData = esContext->userData;

GLbyte vShaderStr[] =

"uniform mat4 u_mvpMatrix;                   \n"

"attribute vec4 a_position;                  \n"

"void main()                                 \n"

"{                                           \n"

"   gl_Position = u_mvpMatrix * a_position;  \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";

// 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" );

// Get the uniform locations

userData->mvpLoc = glGetUniformLocation( userData->programObject, "u_mvpMatrix" );

// Generate the vertex data

userData->numIndices = esGenCube( 1.0, &userData->vertices,

NULL, NULL, &userData->indices );

// Starting rotation angle for the cube

userData->angle = 45.0f;

glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );

return GL_TRUE;

}

void Draw ( ESContext *esContext )

{

UserData *userData = esContext->userData;

// 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, 3, GL_FLOAT,

GL_FALSE, 3 * sizeof(GLfloat), userData->vertices );

glEnableVertexAttribArray ( userData->positionLoc );

// Load the MVP matrix

glUniformMatrix4fv( userData->mvpLoc, 1, GL_FALSE, (GLfloat*) &userData->mvpMatrix.m[0][0] );

// Draw the cube

glDrawElements ( GL_TRIANGLES, userData->numIndices, GL_UNSIGNED_SHORT, userData->indices );

}

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注意: glGetAttribLocation 及 glVertexAttribPointer；

注意: glGetUniformLocation 及 glUniformMatrix4fv；