OpenGL代码学习（11）--抗锯齿

注意：需要在配置好OpenGL的编程环境中运行下列代码，环境配置文章可参考：

OpenGL在Mac项目上的配置

下面的代码，直接放置在main.cpp文件中即可：

#include "GLTools.h"
#include "GLFrustum.h"
#include <GLUT/GLUT.h>

GLShaderManager shaderManager;
GLFrustum viewFrustum;
GLBatch smallStarBatch;
GLBatch mediumStarBatch;
GLBatch largeStarBatch;
GLBatch mountainRangeBatch;
GLBatch moonBatch;

#define SMALL_STARS 100
#define MEDIUM_STARS 40
#define LARGE_STARS 15

#define SCREEN_X 800
#define SCREEN_Y 720

// 点击菜单选项触发的回调方法
void ProcessMenu(int value) {
    switch (value) {
        case 1:
            // 开启抗锯齿处理，必须先开启颜色混合模式
            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
            glEnable(GL_BLEND);
            // 点抗锯齿
            glEnable(GL_POINT_SMOOTH);
            /*
             GL_NICEST:效果最好
             GL_FASTEST:效果最快
             */
            glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
            // 线抗锯齿
            glEnable(GL_LINE_SMOOTH);
            glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
            // 多边形抗锯齿
            glEnable(GL_POLYGON_SMOOTH);
            glHint(GL_POLYGON_SMOOTH_HINT, GL_NICEST);
            break;
        case 2:
            // 关闭抗锯齿处理
            glDisable(GL_BLEND);
            glDisable(GL_POINT_SMOOTH);
            glDisable(GL_LINE_SMOOTH);
            glDisable(GL_POLYGON_SMOOTH);
            break;
        default:
            break;
    }
    // 触发渲染
    glutPostRedisplay();
}

// 渲染画面
void RenderScene(void) {
    // 清除缓存区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    // 设置着色器为单位白色
    GLfloat vWhite[] = {1.0f, 1.0f, 1.0f, 1.0f};
    shaderManager.UseStockShader(GLT_SHADER_FLAT, viewFrustum.GetProjectionMatrix(), vWhite);
    
    // 画小点
    glPointSize(1.0f);
    smallStarBatch.Draw();
    
    // 画大点
    glPointSize(4.0f);
    mediumStarBatch.Draw();
    
    // 画超大点
    glPointSize(8.0f);
    largeStarBatch.Draw();
    
    // 画月亮
    moonBatch.Draw();
    
    // 画山的轮廓
    glLineWidth(3.5);
    mountainRangeBatch.Draw();
    
    // 将在后台缓冲区进行渲染，然后在结束时交换到前台
    glutSwapBuffers();
}

// 初始化小点批次
void SetupSmallStarBatch() {
    M3DVector3f vVerts[SMALL_STARS];
    for (int i = 0; i < SMALL_STARS; i++) {
        vVerts[i][0] = (GLfloat)(rand() % SCREEN_X);
        vVerts[i][1] = (GLfloat)(rand() % (SCREEN_Y -100)) + 100.0f;
        vVerts[i][2] = 0.0f;
    }
    smallStarBatch.Begin(GL_POINTS, SMALL_STARS);
    smallStarBatch.CopyVertexData3f(vVerts);
    smallStarBatch.End();
}

// 初始化大点批次
void SetupMediumStarBatch() {
    M3DVector3f vVerts[MEDIUM_STARS];
    for (int i = 0; i < MEDIUM_STARS; i++) {
        vVerts[i][0] = (GLfloat)(rand() % SCREEN_X);
        vVerts[i][1] = (GLfloat)(rand() % (SCREEN_Y -100)) + 100.0f;
        vVerts[i][2] = 0.0f;
    }
    mediumStarBatch.Begin(GL_POINTS, MEDIUM_STARS);
    mediumStarBatch.CopyVertexData3f(vVerts);
    mediumStarBatch.End();
}

// 初始化超大点批次
void SetupLargeStarBatch() {
    M3DVector3f vVerts[LARGE_STARS];
    for (int i = 0; i < LARGE_STARS; i++) {
        vVerts[i][0] = (GLfloat)(rand() % SCREEN_X);
        vVerts[i][1] = (GLfloat)(rand() % (SCREEN_Y -100)) + 100.0f;
        vVerts[i][2] = 0.0f;
    }
    largeStarBatch.Begin(GL_POINTS, LARGE_STARS);
    largeStarBatch.CopyVertexData3f(vVerts);
    largeStarBatch.End();
}

// 初始化山轮廓批次
void SetupMountainRangeBatch() {
    M3DVector3f vMountains[12] = {
        0.0f, 25.0f, 0.0f,
        50.0f, 100.0f, 0.0f,
        100.0f, 25.0f, 0.0f,
        225.0f, 125.0f, 0.0f,
        300.0f, 50.0f, 0.0f,
        375.0f, 100.0f, 0.0f,
        460.0f, 25.0f, 0.0f,
        525.0f, 100.0f, 0.0f,
        600.0f, 20.0f, 0.0f,
        675.0f, 70.0f, 0.0f,
        750.0f, 25.0f, 0.0f,
        800.0f, 90.0f, 0.0f
    };
    mountainRangeBatch.Begin(GL_LINE_STRIP, 12);
    mountainRangeBatch.CopyVertexData3f(vMountains);
    mountainRangeBatch.End();
}

// 初始化月亮批次
void SetupMoonBatch() {
    GLfloat x = 700.0f;
    GLfloat y = 500.0f;
    GLfloat r = 50.0f;
    M3DVector3f vVerts[SMALL_STARS];
    int nVerts = 0;
    vVerts[nVerts][0] = x;
    vVerts[nVerts][1] = y;
    vVerts[nVerts][2] = 0.0f;
    for (GLfloat angle = 0; angle < M3D_2PI; angle += 0.2f) {
        nVerts++;
        vVerts[nVerts][0] = x + float(cos(angle)) * r;
        vVerts[nVerts][1] = y + float(sin(angle)) * r;
        vVerts[nVerts][2] = 0.0f;
    }
    nVerts++;
    vVerts[nVerts][0] = x + r;
    vVerts[nVerts][1] = y;
    vVerts[nVerts][2] = 0.0f;
    
    moonBatch.Begin(GL_TRIANGLE_FAN, 34);
    moonBatch.CopyVertexData3f(vVerts);
    moonBatch.End();
}

// 程序一次性初始化
void SetupRC() {
    // 设置背景色为黑色
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    
    // 初始化着色器管理者
    shaderManager.InitializeStockShaders();
    
    // 初始化各个图元批次
    SetupSmallStarBatch();
    SetupMediumStarBatch();
    SetupLargeStarBatch();
    SetupMountainRangeBatch();
    SetupMoonBatch();
}

// 窗口大小改变时接受新的宽度和高度
void ChangeSize(int w, int h) {
    glViewport(0, 0, w, h);
    // 正投影
    viewFrustum.SetOrthographic(0.0f, SCREEN_X, 0.0f, SCREEN_Y, -1.0f, 1.0f);
}

// 程序入口
int main(int argc, char *argv[]) {
    // 设置当前工作目录，针对Mac OS X
    gltSetWorkingDirectory(argv[0]);
    
    // GLUT初始化
    glutInit(&argc, argv);
    
    /*
     初始化渲染模式，其中标志GLUT_DOUBLE、GLUT_RGBA、GLUT_DEPTH、GLUT_STENCILf分别指双缓冲窗口、RGBA颜色模式、深度测试、模板缓冲区
     */
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
    
    // 初始化窗口大小
    glutInitWindowSize(800, 720);
    
    // 创建窗口
    glutCreateWindow("Smoothing Out The Jaggies");
    
    // 创建菜单并绑定回调函数，添加选项，确定右键触发
    glutCreateMenu(ProcessMenu);
    glutAddMenuEntry("Antialiased Rendering", 1);
    glutAddMenuEntry("Normal Rendering", 2);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
    
    // 注册回调函数
    glutReshapeFunc(ChangeSize);
    glutDisplayFunc(RenderScene);
    
    // 确保驱动程序的初始化中没有出现任何问题
    GLenum err = glewInit();
    if (err != GLEW_OK) {
        fprintf(stderr, "glew error:%s
", glewGetErrorString(err));
        return 1;
    }
    
    // 初始化设置
    SetupRC();
    
    // 进入调用循环
    glutMainLoop();
    
    return 0;
}

运行代码后的效果（普通，非抗锯齿模式）：

抗锯齿模式的对比图：