OpenGL着色器（二）

ProvokingVertex.vp

// ProvokingVertex flat shader demo// Vertex Shader// Richard S. Wright Jr.// OpenGL SuperBible#version 130in vec4 vColor;in vec4 vVertex;flat out vec4 vVaryingColor;void main(void)     {     vVaryingColor = vColor;    gl_Position = vVertex;    }

ProvokingVertex.fp

// ProvokingVertex flat shader demo// Fragment Shader// Richard S. Wright Jr.// OpenGL SuperBible#version 130out vec4 vFragColor;flat in vec4 vVaryingColor;void main(void)   {    vFragColor = vVaryingColor;   }

ProvokingVertex.cpp

// ProvokingVertex.cpp// Our first OpenGL program that will just draw a triangle on the screen.#include <GLTools.h>            // OpenGL toolkit#include <GLShaderManager.h>    // Shader Manager Class#ifdef __APPLE__#include <glut/glut.h>          // OS X version of GLUT#else#define FREEGLUT_STATIC#include <GL/glut.h>            // Windows FreeGlut equivalent#endifGLBatchtriangleBatch;GLShaderManagershaderManager;GLintmyIdentityShader;///////////////////////////////////////////////////////////////////////////////// Window has changed size, or has just been created. In either case, we need// to use the window dimensions to set the viewport and the projection matrix.void ChangeSize(int w, int h)    {glViewport(0, 0, w, h);    }///////////////////////////////////////////////////////////////////////////////// This function does any needed initialization on the rendering context. // This is the first opportunity to do any OpenGL related tasks.void SetupRC(){// Blue backgroundglClearColor(0.0f, 0.0f, 0.0f, 1.0f );    shaderManager.InitializeStockShaders();// Load up a triangleGLfloat vVerts[] = { -0.5f, 0.0f, 0.0f,                   0.5f, 0.0f, 0.0f,  0.0f, 0.5f, 0.0f };GLfloat vColors [] = { 1.0f, 0.0f, 0.0f, 1.0f,                   0.0f, 1.0f, 0.0f, 1.0f,   0.0f, 0.0f, 1.0f, 1.0f };triangleBatch.Begin(GL_TRIANGLES, 3);triangleBatch.CopyVertexData3f(vVerts);triangleBatch.CopyColorData4f(vColors);triangleBatch.End();myIdentityShader = gltLoadShaderPairWithAttributes("ProvokingVertex.vp", "ProvokingVertex.fp", 2,                             GLT_ATTRIBUTE_VERTEX, "vVertex", GLT_ATTRIBUTE_COLOR, "vColor");glProvokingVertex(GL_FIRST_VERTEX_CONVENTION);}///////////////////////////////////////////////////////////////////////////////// Cleanupvoid ShutdownRC()   {   glDeleteProgram(myIdentityShader);   }///////////////////////////////////////////////////////////////////////////////// Called to draw scenevoid RenderScene(void){// Clear the window with current clearing colorglClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);glUseProgram(myIdentityShader);triangleBatch.Draw();// Perform the buffer swap to display back bufferglutSwapBuffers();}int nToggle = 1;void KeyPressFunc(unsigned char key, int x, int y){if(key == 32){nToggle++;if(nToggle %2 == 0) {glProvokingVertex(GL_LAST_VERTEX_CONVENTION);glutSetWindowTitle("Provoking Vertex - Last Vertex - Press Space Bars");}else {glProvokingVertex(GL_FIRST_VERTEX_CONVENTION);glutSetWindowTitle("Provoking Vertex - First Vertex - Press Space Bars");}glutPostRedisplay();}}       ///////////////////////////////////////////////////////////////////////////////// Main entry point for GLUT based programsint main(int argc, char* argv[]){gltSetWorkingDirectory(argv[0]);glutInit(&argc, argv);glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);glutInitWindowSize(800, 600);glutCreateWindow("Provoking Vertex - First Vertex - Press Space Bars");    glutReshapeFunc(ChangeSize);    glutDisplayFunc(RenderScene);glutKeyboardFunc(KeyPressFunc);GLenum err = glewInit();if (GLEW_OK != err) {fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));return 1;}SetupRC();glutMainLoop();ShutdownRC();return 0;}