4.1案例-模型视图投影矩阵

#include "GLTools.h"
#include "GLMatrixStack.h"
#include "GLFrame.h"
#include "GLFrustum.h"
#include "GLGeometryTransform.h"
#include "GLBatch.h"
#include "StopWatch.h"

#include <math.h>
#ifdef __APPLE__
#include <glut/glut.h>
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>
#endif

GLFrustum viewFrustum;
GLShaderManager shaderManager;
GLTriangleBatch torusBatch;
GLGeometryTransform transformPipeline;

//窗口改变时接受新的宽度和高度，0，0代表窗口中视口的左下角坐标，w,h代表像素
void ChangeSize(int w, int h) {
    //防止除以0
    if (h == 0) {
        h = 1;
    }
    glViewport(0, 0, w, h);
    viewFrustum.SetPerspective(35, float(w) / float(h) , 1, 1000); //设置透视投影
}

//开始渲染
void renderScene(void) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //建立基于时间变化的动画
    static CStopWatch rotTimer;
    //当前时间*60s
    float yRot = rotTimer.GetElapsedSeconds() * 60;
    //平移 旋转 视图 视图投影MVP
    M3DMatrix44f mTranslate, mRotate, mModelView, mModelViewProjection;
    //创建一个4*4矩阵变量，将花托沿着z轴复负方向移动2.5个单位长度
    m3dTranslationMatrix44(mTranslate, 0, 0, -2.5);
    //创建一个4*4矩阵变量，将花托在y轴上渲染yRot度，yRot根据经过时间设置动画帧率 也可设置x轴
    m3dRotationMatrix44(mRotate, m3dDegToRad(yRot), 0, 1, 0);
    //mTranslate 和mRotate 相乘放到 mModelView
    m3dMatrixMultiply44(mModelView, mTranslate, mRotate);
    //投影*模型!=模型*投影
    m3dMatrixMultiply44(mModelViewProjection, viewFrustum.GetProjectionMatrix(), mModelView);
    
    GLfloat vBlack[] = { 0, 0, 0, 1 };
    //通过平面着色器提交矩阵和颜色
    shaderManager.UseStockShader(GLT_SHADER_FLAT, mModelViewProjection, vBlack);
    //开始绘图
    torusBatch.Draw();
    //交换缓冲区
    glutSwapBuffers();
    //刷新
    glutPostRedisplay();
    
}

//为程序做一次性的设置
void setupRC() {
    glClearColor(0.8, 0.8, 0.8, 1);
    shaderManager.InitializeStockShaders();
    glEnable(GL_DEPTH_TEST);
    
    //形成一个球
    gltMakeSphere(torusBatch, 0.4, 10, 20);
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
}

int main(int argc, char *argv[]) {
    gltSetWorkingDirectory(argv[0]);
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);
    glutInitWindowSize(800, 600);
    glutCreateWindow("ModelViewProjection Example");
    glutReshapeFunc(ChangeSize);
    glutDisplayFunc(renderScene);
    GLenum err = glewInit();
    if (err != GLEW_OK) {
        fprintf(stderr, "GLEW Error:%s\n",glewGetErrorString(err));
        return 1;
    }
    setupRC();
    glutMainLoop();
    return 0;
}