# OpenGL ES 案例 - 实现一个有纹理的立方体

效果如下图


旋转效果.gif

1.定义一个结构体

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

2.相关属性设置

@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;

3. OpenGL ES 相关初始化

- (void) commonInit{
//    1、创建context
    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
    [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、使用深度测试
    self.glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    glDepthRangef(1, 0);
    
//    4、将glkView加入到view上
    [self.view addSubview:self.glkView];
    
//    5、获取纹理图片
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"timg" ofType:@"jpeg"];
    UIImage *image = [UIImage imageWithContentsOfFile:filePath];
    
//    6、设置纹理参数
    NSDictionary *options = @{GLKTextureLoaderOriginBottomLeft: @(YES)};
    GLKTextureInfo *textureInfo = [GLKTextureLoader textureWithCGImage:[image CGImage] options:options error:NULL];
    
//    7、使用effect
    self.baseEffect = [[GLKBaseEffect alloc] init];
    self.baseEffect.texture2d0.name = textureInfo.name;
    self.baseEffect.texture2d0.target = textureInfo.target;
    
//    光照
    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);
    
}

4.加载顶点/纹理坐标数据

- (void)setupVertex{
    
    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}};
    
//    开辟缓存区
    glGenBuffers(1, &_vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(CCVertex)*kCoordCount, 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));
    
//    光照
    glEnableVertexAttribArray(GLKVertexAttribNormal);
    glVertexAttribPointer(GLKVertexAttribNormal, 3, GL_FLOAT, GL_FALSE, sizeof(CCVertex), NULL+offsetof(CCVertex, normal));
}


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

5. GLKViewDelegate

-(void)glkView:(GLKView *)view drawInRect:(CGRect)rect{

//    开启深度测试
    glEnable(GL_DEPTH_TEST);
    
//    清除缓存区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
//    准备绘制
    [self.baseEffect prepareToDraw];
    
//    绘图(数组绘制)
    glDrawArrays(GL_TRIANGLES, 0, kCoordCount);
   
}

6.添加定时器

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

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

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