OpenGL 使用矩阵变换改变视图

在上一篇OpenGL 深度测试基础上修改 main.cpp 文件，完成此 demo 。

代码

本篇主要是使用矩阵相关操作，来完成视图的变换。与之前 demo 的区别在与，之前通过改变观察点位置来获取不同位置物体的视图。次 demo 则是直接通过矩阵变换修改物体的位置，来让观察者看到不同位置的物体。代码如下：

#include "GLMatrixStack.h"
#include "GLFrame.h"
#include "GLFrustum.h"
#include "GLBatch.h"
#include "GLGeometryTransform.h"
#include <math.h>
#include <GLUT/GLUT.h>
#include "GLTools.h"
#include "StopWatch.h"

GLShaderManager  shaderManager;
GLMatrixStack    modelViewMatrix;

//投影矩阵
GLFrustum        viewFrustum;
GLTriangleBatch cylinderBatch;

void changeSize(int w, int h) {
    glViewport(0, 0, w, h);
    //设置透视投影
    viewFrustum.SetPerspective(30.0f, float(w) / float(h), 2.0f, 400.0f);
    
}

void renderScene() {
    //清理缓冲区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
    
    static CStopWatch rotTimer;
    float yRot = rotTimer.GetElapsedSeconds() * 30;
    
    M3DMatrix44f mTranslate, mRotate, mModelView, mModelViewProjection;
    //创建平移矩阵
    m3dTranslationMatrix44(mTranslate,0.0f,0.0f,-8.0f);
    //创建旋转矩阵
    m3dRotationMatrix44(mRotate, m3dDegToRad(yRot), 0.0f,1.0f,0.0f);
    //模型矩阵 = 旋转矩阵 * 平移矩阵
    m3dMatrixMultiply44(mModelView, mTranslate, mRotate);
    //模型视图矩阵 = 视图矩阵 * 模型矩阵
    m3dMatrixMultiply44(mModelViewProjection, viewFrustum.GetProjectionMatrix(), mModelView);
    
    GLfloat vOrange[] = {1.0f,0.6f,0.0f,1.0f};
    shaderManager.UseStockShader(GLT_SHADER_FLAT,mModelViewProjection,vOrange);
    cylinderBatch.Draw();
    glutSwapBuffers();
    glutPostRedisplay();
}

void setupRC() {
    glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
    shaderManager.InitializeStockShaders();
    glEnable(GL_DEPTH_TEST);
    gltMakeCylinder(cylinderBatch, 0.3f, 0.8f, 0.8f, 100, 1);
    
}

int main(int argc, char* argv[]) {
    
    gltSetWorkingDirectory(argv[0]);
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);
    glutInitWindowSize(600, 600);
    glutCreateWindow("dowZhang");
    glutReshapeFunc(changeSize);
    glutDisplayFunc(renderScene);
    
    GLenum err = glewInit();
    if (GLEW_OK != err) {
        return 1;
    }
    
    setupRC();
    
    glutMainLoop();
    
    return 0;
}

复制代码

效果如下：