OpenGL ES: GLKit实现正方体旋转

作者: 星星1024 | 来源:发表于2020-07-28 21:53 被阅读0次

OpenGL ES 案例 - 正方体的渲染+旋转
OpenGL ES: GLKit实现正方体旋转
OpenGL ES - GLKit（GLKBaseEffect）
初识GLKit
OpenGL ES 编程指南三：OpenGL ES和GLKit绘
OpenGL ES学习:渲染正方体并旋转
GLKit 及常用 API
二、GLKit 及常见API
GLES-02-GLKit
用GLKit写出旋转的效果

实现正方体旋转分为4个步骤:

OpenGL 初始化, 加载纹理
设置定时器
GLKViewDelegate函数绘制
设置旋转

一. OpenGL 初始化

声明变量和结构图

typedef struct {
    GLKVector3 positionCoord;   //顶点坐标
    GLKVector2 textureCoord;    //纹理坐标
    GLKVector3 normal;          //法线
} CCVertex;

// 顶点数
static NSInteger const kCoordCount = 36;

@interface CubeViewController () <GLKViewDelegate>

@property (nonatomic, strong) GLKView *glkView;
@property (nonatomic, strong) GLKBaseEffect *baseEffect;
@property (nonatomic, assign) CCVertex *vertices;

@property (nonatomic, strong) CADisplayLink *displayLink;
@property (nonatomic, assign) NSInteger angle;
@property (nonatomic, assign) GLuint vertexBuffer;

@end

OpenGL ES 初始化

//1.创建context
    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    //设置当前context
    [EAGLContext setCurrentContext:context];

    //2.创建GLKView并设置代理
    CGRect frame = CGRectMake(0, 100, self.view.frame.size.width, self.view.frame.size.width);
    self.glkView = [[GLKView alloc] initWithFrame:frame context:context];
    self.glkView.backgroundColor = [UIColor clearColor];
    self.glkView.delegate = self;

    //3.使用深度缓存
    self.glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    //默认是(0, 1)，这里用于翻转 z 轴，使正方形朝屏幕外
    glDepthRangef(1, 0);

    //4.将GLKView 添加self.view 上
    [self.view addSubview:self.glkView];

    //5.获取纹理图片
    NSString *imagePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"car.jpeg"];
    UIImage *image = [UIImage imageWithContentsOfFile:imagePath];

    //6.设置纹理参数
    NSDictionary *options = @{ GLKTextureLoaderOriginBottomLeft: @(YES) };
    GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithCGImage:image.CGImage options:options error:NULL];
    //7.使用baseEffect
    self.baseEffect = [[GLKBaseEffect alloc] init];
    self.baseEffect.texture2d0.name = textureInfo.name;
    self.baseEffect.texture2d0.target = textureInfo.target;
    //开启光照效果
    self.baseEffect.light0.enabled = YES;
    //漫反射颜色
    self.baseEffect.light0.diffuseColor = GLKVector4Make(1, 1, 1, 1);
    //光源位置
    self.baseEffect.light0.position = GLKVector4Make(-0.5, -0.5, 5, 1);
 /*
     解释一下:
     这里我们不复用顶点，使用每 3 个点画一个三角形的方式，需要 12 个三角形，则需要 36 个顶点
     以下的数据用来绘制以（0，0，0）为中心，边长为 1 的立方体
     */

    //8. 开辟顶点数据空间(数据结构SenceVertex 大小 * 顶点个数kCoordCount)
    self.vertices = malloc(sizeof(CCVertex) * kCoordCount);

    // 前面
    self.vertices[0] = (CCVertex) { { -0.5, 0.5, 0.5 }, { 0, 1 }, { 0, 0, 1 } };
    self.vertices[1] = (CCVertex) { { -0.5, -0.5, 0.5 }, { 0, 0 }, { 0, 0, 1 } };
    self.vertices[2] = (CCVertex) { { 0.5, 0.5, 0.5 }, { 1, 1 }, { 0, 0, 1 } };
    self.vertices[3] = (CCVertex) { { -0.5, -0.5, 0.5 }, { 0, 0 }, { 0, 0, 1 } };
    self.vertices[4] = (CCVertex) { { 0.5, 0.5, 0.5 }, { 1, 1 }, { 0, 0, 1 } };
    self.vertices[5] = (CCVertex) { { 0.5, -0.5, 0.5 }, { 1, 0 }, { 0, 0, 1 } };

    // 上面
    self.vertices[6] = (CCVertex) { { 0.5, 0.5, 0.5 }, { 1, 1 }, { 0, 1, 0 } };
    self.vertices[7] = (CCVertex) { { -0.5, 0.5, 0.5 }, { 0, 1 }, { 0, 1, 0 } };
    self.vertices[8] = (CCVertex) { { 0.5, 0.5, -0.5 }, { 1, 0 }, { 0, 1, 0 } };
    self.vertices[9] = (CCVertex) { { -0.5, 0.5, 0.5 }, { 0, 1 }, { 0, 1, 0 } };
    self.vertices[10] = (CCVertex) { { 0.5, 0.5, -0.5 }, { 1, 0 }, { 0, 1, 0 } };
    self.vertices[11] = (CCVertex) { { -0.5, 0.5, -0.5 }, { 0, 0 }, { 0, 1, 0 } };

    // 下面
    self.vertices[12] = (CCVertex) { { 0.5, -0.5, 0.5 }, { 1, 1 }, { 0, -1, 0 } };
    self.vertices[13] = (CCVertex) { { -0.5, -0.5, 0.5 }, { 0, 1 }, { 0, -1, 0 } };
    self.vertices[14] = (CCVertex) { { 0.5, -0.5, -0.5 }, { 1, 0 }, { 0, -1, 0 } };
    self.vertices[15] = (CCVertex) { { -0.5, -0.5, 0.5 }, { 0, 1 }, { 0, -1, 0 } };
    self.vertices[16] = (CCVertex) { { 0.5, -0.5, -0.5 }, { 1, 0 }, { 0, -1, 0 } };
    self.vertices[17] = (CCVertex) { { -0.5, -0.5, -0.5 }, { 0, 0 }, { 0, -1, 0 } };

    // 左面
    self.vertices[18] = (CCVertex) { { -0.5, 0.5, 0.5 }, { 1, 1 }, { -1, 0, 0 } };
    self.vertices[19] = (CCVertex) { { -0.5, -0.5, 0.5 }, { 0, 1 }, { -1, 0, 0 } };
    self.vertices[20] = (CCVertex) { { -0.5, 0.5, -0.5 }, { 1, 0 }, { -1, 0, 0 } };
    self.vertices[21] = (CCVertex) { { -0.5, -0.5, 0.5 }, { 0, 1 }, { -1, 0, 0 } };
    self.vertices[22] = (CCVertex) { { -0.5, 0.5, -0.5 }, { 1, 0 }, { -1, 0, 0 } };
    self.vertices[23] = (CCVertex) { { -0.5, -0.5, -0.5 }, { 0, 0 }, { -1, 0, 0 } };

    // 右面
    self.vertices[24] = (CCVertex) { { 0.5, 0.5, 0.5 }, { 1, 1 }, { 1, 0, 0 } };
    self.vertices[25] = (CCVertex) { { 0.5, -0.5, 0.5 }, { 0, 1 }, { 1, 0, 0 } };
    self.vertices[26] = (CCVertex) { { 0.5, 0.5, -0.5 }, { 1, 0 }, { 1, 0, 0 } };
    self.vertices[27] = (CCVertex) { { 0.5, -0.5, 0.5 }, { 0, 1 }, { 1, 0, 0 } };
    self.vertices[28] = (CCVertex) { { 0.5, 0.5, -0.5 }, { 1, 0 }, { 1, 0, 0 } };
    self.vertices[29] = (CCVertex) { { 0.5, -0.5, -0.5 }, { 0, 0 }, { 1, 0, 0 } };

    // 后面
    self.vertices[30] = (CCVertex) { { -0.5, 0.5, -0.5 }, { 0, 1 }, { 0, 0, -1 } };
    self.vertices[31] = (CCVertex) { { -0.5, -0.5, -0.5 }, { 0, 0 }, { 0, 0, -1 } };
    self.vertices[32] = (CCVertex) { { 0.5, 0.5, -0.5 }, { 1, 1 }, { 0, 0, -1 } };
    self.vertices[33] = (CCVertex) { { -0.5, -0.5, -0.5 }, { 0, 0 }, { 0, 0, -1 } };
    self.vertices[34] = (CCVertex) { { 0.5, 0.5, -0.5 }, { 1, 1 }, { 0, 0, -1 } };
    self.vertices[35] = (CCVertex) { { 0.5, -0.5, -0.5 }, { 1, 0 }, { 0, 0, -1 } };

    //开辟顶点缓存区
    glGenBuffers(1, &_vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
    GLsizeiptr bufferSizeBytes = sizeof(CCVertex) * kCoordCount;
    glBufferData(GL_ARRAY_BUFFER, bufferSizeBytes, self.vertices, GL_STATIC_DRAW);

    //顶点数据
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(CCVertex), NULL + offsetof(CCVertex, positionCoord));

    //纹理数据
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(CCVertex), NULL + offsetof(CCVertex, textureCoord));

    //法线数据
    glEnableVertexAttribArray(GLKVertexAttribNormal);
    glVertexAttribPointer(GLKVertexAttribNormal, 3, GL_FLOAT, GL_FALSE, sizeof(CCVertex), NULL + offsetof(CCVertex, normal));

二. 添加定时器

    self.angle = 0;
    self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
    [self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];

三. GLKViewDelegate 函数

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
    //1.开启深度测试
    glEnable(GL_DEPTH_TEST);
    //2.清除颜色缓存区&深度缓存区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //3.准备绘制
    [self.baseEffect prepareToDraw];
    //4.绘图
    glDrawArrays(GL_TRIANGLES, 0, kCoordCount);
}

四. 设置旋转

  //1.计算旋转度数
    self.angle = (self.angle + 5) % 360;
    //2.修改baseEffect.transform.modelviewMatrix
    self.baseEffect.transform.modelviewMatrix = GLKMatrix4MakeRotation(GLKMathDegreesToRadians(self.angle), 0.3, 1, 0.7);
    //3.重新渲染
    [self.glkView display];

附加载过程图

OpenGL ES_GLKView正方体旋转.png