| // |
| // 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 |
| // |
| |
| // Simple_VertexShader.c |
| // |
| // This is a simple example that draws a rotating cube in perspective |
| // using a vertex shader to transform the object |
| // |
| #include <stdlib.h> |
| #include "esUtil.h" |
| |
| typedef struct |
| { |
| // Handle to a program object |
| GLuint programObject; |
| |
| // Attribute locations |
| GLint positionLoc; |
| |
| // Uniform locations |
| GLint mvpLoc; |
| |
| // Vertex daata |
| GLfloat *vertices; |
| GLushort *indices; |
| int numIndices; |
| |
| // Rotation angle |
| GLfloat angle; |
| |
| // MVP matrix |
| ESMatrix mvpMatrix; |
| } UserData; |
| |
| /// |
| // Initialize the shader and program object |
| // |
| int Init ( ESContext *esContext ) |
| { |
| 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 TRUE; |
| } |
| |
| |
| /// |
| // Update MVP matrix based on time |
| // |
| void Update ( ESContext *esContext, float deltaTime ) |
| { |
| UserData *userData = (UserData*) esContext->userData; |
| ESMatrix perspective; |
| ESMatrix modelview; |
| float aspect; |
| |
| // Compute a rotation angle based on time to rotate the cube |
| userData->angle += ( deltaTime * 40.0f ); |
| if( userData->angle >= 360.0f ) |
| userData->angle -= 360.0f; |
| |
| // Compute the window aspect ratio |
| aspect = (GLfloat) esContext->width / (GLfloat) esContext->height; |
| |
| // Generate a perspective matrix with a 60 degree FOV |
| esMatrixLoadIdentity( &perspective ); |
| esPerspective( &perspective, 60.0f, aspect, 1.0f, 20.0f ); |
| |
| // Generate a model view matrix to rotate/translate the cube |
| esMatrixLoadIdentity( &modelview ); |
| |
| // Translate away from the viewer |
| esTranslate( &modelview, 0.0, 0.0, -2.0 ); |
| |
| // Rotate the cube |
| esRotate( &modelview, userData->angle, 1.0, 0.0, 1.0 ); |
| |
| // Compute the final MVP by multiplying the |
| // modevleiw and perspective matrices together |
| esMatrixMultiply( &userData->mvpMatrix, &modelview, &perspective ); |
| } |
| |
| /// |
| // Draw a triangle using the shader pair created in Init() |
| // |
| 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 ); |
| |
| eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface ); |
| } |
| |
| /// |
| // Cleanup |
| // |
| void ShutDown ( ESContext *esContext ) |
| { |
| UserData *userData = esContext->userData; |
| |
| if ( userData->vertices != NULL ) |
| { |
| free ( userData->vertices ); |
| } |
| |
| if ( userData->indices != NULL ) |
| { |
| free ( userData->indices ); |
| } |
| |
| // Delete program object |
| glDeleteProgram ( userData->programObject ); |
| } |
| |
| |
| int main ( int argc, char *argv[] ) |
| { |
| ESContext esContext; |
| UserData userData; |
| |
| esInitContext ( &esContext ); |
| esContext.userData = &userData; |
| |
| esCreateWindow ( &esContext, TEXT("Simple Vertex Shader"), 320, 240, ES_WINDOW_RGB ); |
| |
| if ( !Init ( &esContext ) ) |
| return 0; |
| |
| esRegisterDrawFunc ( &esContext, Draw ); |
| esRegisterUpdateFunc ( &esContext, Update ); |
| |
| esMainLoop ( &esContext ); |
| |
| ShutDown ( &esContext ); |
| } |