一、思维导图
OpenGL ES GLKit 加载立方体.jpeg
主要分3个部分：
- OpenGL ES 的相关初始化
- 设置顶点/纹理坐标数据
- 添加CADisplayLink使正方体动起来
二、示例代码
1. 定义必要的参数
#import <GLKit/GLKit.h>
#import "CubeViewController.h"
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
2. viewDidLoad方法
- (void)viewDidLoad {
[super viewDidLoad];
//1.View背景色
self.view.backgroundColor = [UIColor blackColor];
//2. OpenGL ES 相关初始化
[self commonInit];
//3.顶点/纹理坐标数据
[self vertexDataSetup];
//4. 添加CADisplayLink
[self addCADisplayLink];
}
3. OpenGL ES相关初始化和设置
- (void)commonInit {
//1.创建context
EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
//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:@"kunkun.jpg"];
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;
}
4. 加载顶点和纹理坐标数据
-(void)vertexDataSetup
{
/*
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}};
self.vertices[1] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 0}};
self.vertices[2] = (CCVertex){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[3] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 0}};
self.vertices[4] = (CCVertex){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[5] = (CCVertex){{0.5, -0.5, 0.5}, {1, 0}};
// 上面
self.vertices[6] = (CCVertex){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[7] = (CCVertex){{-0.5, 0.5, 0.5}, {0, 1}};
self.vertices[8] = (CCVertex){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[9] = (CCVertex){{-0.5, 0.5, 0.5}, {0, 1}};
self.vertices[10] = (CCVertex){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[11] = (CCVertex){{-0.5, 0.5, -0.5}, {0, 0}};
// 下面
self.vertices[12] = (CCVertex){{0.5, -0.5, 0.5}, {1, 1}};
self.vertices[13] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[14] = (CCVertex){{0.5, -0.5, -0.5}, {1, 0}};
self.vertices[15] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[16] = (CCVertex){{0.5, -0.5, -0.5}, {1, 0}};
self.vertices[17] = (CCVertex){{-0.5, -0.5, -0.5}, {0, 0}};
// 左面
self.vertices[18] = (CCVertex){{-0.5, 0.5, 0.5}, {1, 1}};
self.vertices[19] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[20] = (CCVertex){{-0.5, 0.5, -0.5}, {1, 0}};
self.vertices[21] = (CCVertex){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[22] = (CCVertex){{-0.5, 0.5, -0.5}, {1, 0}};
self.vertices[23] = (CCVertex){{-0.5, -0.5, -0.5}, {0, 0}};
// 右面
self.vertices[24] = (CCVertex){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[25] = (CCVertex){{0.5, -0.5, 0.5}, {0, 1}};
self.vertices[26] = (CCVertex){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[27] = (CCVertex){{0.5, -0.5, 0.5}, {0, 1}};
self.vertices[28] = (CCVertex){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[29] = (CCVertex){{0.5, -0.5, -0.5}, {0, 0}};
// 后面
self.vertices[30] = (CCVertex){{-0.5, 0.5, -0.5}, {0, 1}};
self.vertices[31] = (CCVertex){{-0.5, -0.5, -0.5}, {0, 0}};
self.vertices[32] = (CCVertex){{0.5, 0.5, -0.5}, {1, 1}};
self.vertices[33] = (CCVertex){{-0.5, -0.5, -0.5}, {0, 0}};
self.vertices[34] = (CCVertex){{0.5, 0.5, -0.5}, {1, 1}};
self.vertices[35] = (CCVertex){{0.5, -0.5, -0.5}, {1, 0}};
//开辟缓存区 VBO
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));
}
5. GLKViewDelegate 的 drawInRect 方法
#pragma mark - GLKViewDelegate
- (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);
}
6. CADisplayLink 使立方体动起来
-(void) addCADisplayLink{
//CADisplayLink 类似定时器,提供一个周期性调用.属于QuartzCore.framework中.
//具体可以参考该博客 https://www.cnblogs.com/panyangjun/p/4421904.html
self.angle = 0;
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
[self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
}
#pragma mark - update
- (void)update {
//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];
}
7. dealloc 的 release 操作
- (void)dealloc {
if ([EAGLContext currentContext] == self.glkView.context) {
[EAGLContext setCurrentContext:nil];
}
if (_vertices) {
free(_vertices);
_vertices = nil;
}
if (_vertexBuffer) {
glDeleteBuffers(1, &_vertexBuffer);
_vertexBuffer = 0;
}
//displayLink 失效
[self.displayLink invalidate];
}
三、效果
效果.gif
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