kc3-lang/angle/samples/gles2_book/Simple_VertexShader/Simple_VertexShader.c

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• Hash : 0270ef14
  Author :
  Date : 2010-04-07T19:57:20
  

  Changed the default character set to be UNICODE, the same as chromium. Changes to fix compile errors and warnings.
  Review URL: http://codereview.appspot.com/816046
  
  git-svn-id: https://angleproject.googlecode.com/svn/trunk@103 736b8ea6-26fd-11df-bfd4-992fa37f6226
  

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• samples/gles2_book/Simple_VertexShader/Simple_VertexShader.c

• //
  // 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 );
  }
  

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