首先在 xcode 中新建一个工程，并导入一张图片。然后在 ViewController.m 写入以下代码：
#import "ViewController.h"
#import <GLKit/GLKit.h>
typedef struct {
GLKVector3 vertexCoordinate; //顶点坐标
GLKVector2 textureCoordinate; //纹理坐标
}VertexData;
//顶点数
static NSInteger const kVertexCount = 36;
@interface ViewController ()<GLKViewDelegate>
@property(nonatomic,strong)GLKView * glkView;
@property(nonatomic,strong)GLKBaseEffect * baseEffect;
@property(nonatomic,assign)VertexData * vertices;
@property(nonatomic,strong)CADisplayLink * displayLink;
@property(nonatomic,assign)NSInteger angle;
@property(nonatomic,assign)GLuint * vertexBuffer;
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//1.设置背景颜色
self.view.backgroundColor = [UIColor blackColor];
//2.设置 OpenGL ES 相关初始化配置
[self setUpConfig];
//3.图形相关的顶点/纹理坐标数据
[self setUpVertexData];
//4.添加CADisplayLink
[self addCADisplayLink];
}
-(void)setUpConfig
{
//1.创建context并设置当前context
EAGLContext * context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
[EAGLContext setCurrentContext:context];
//2.创建GLKView并设置代理
self.glkView = [[GLKView alloc] initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, self.view.bounds.size.width) context:context];
self.glkView.backgroundColor = [UIColor clearColor];
self.glkView.delegate = self;
//3.设置使用的深度缓冲区个数
self.glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
//4.添加GLKView
[self.view addSubview:self.glkView];
//5.获取纹理图片
NSString * filePath = [[NSBundle mainBundle] pathForResource:@"mei" ofType:@"jpg"];
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.创建GLKBaseEffect
self.baseEffect = [[GLKBaseEffect alloc] init];
self.baseEffect.texture2d0.name = textureInfo.name;
self.baseEffect.texture2d0.target = textureInfo.target;
}
-(void)setUpVertexData
{
//1.开辟顶点数据空间
self.vertices = malloc(sizeof(VertexData) * kVertexCount);
//2.设置顶点/纹理坐标数据
// 前面
self.vertices[0] = (VertexData){{-0.5, 0.5, 0.5}, {0, 1}};
self.vertices[1] = (VertexData){{-0.5, -0.5, 0.5}, {0, 0}};
self.vertices[2] = (VertexData){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[3] = (VertexData){{-0.5, -0.5, 0.5}, {0, 0}};
self.vertices[4] = (VertexData){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[5] = (VertexData){{0.5, -0.5, 0.5}, {1, 0}};
// 上面
self.vertices[6] = (VertexData){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[7] = (VertexData){{-0.5, 0.5, 0.5}, {0, 1}};
self.vertices[8] = (VertexData){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[9] = (VertexData){{-0.5, 0.5, 0.5}, {0, 1}};
self.vertices[10] = (VertexData){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[11] = (VertexData){{-0.5, 0.5, -0.5}, {0, 0}};
// 下面
self.vertices[12] = (VertexData){{0.5, -0.5, 0.5}, {1, 1}};
self.vertices[13] = (VertexData){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[14] = (VertexData){{0.5, -0.5, -0.5}, {1, 0}};
self.vertices[15] = (VertexData){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[16] = (VertexData){{0.5, -0.5, -0.5}, {1, 0}};
self.vertices[17] = (VertexData){{-0.5, -0.5, -0.5}, {0, 0}};
// 左面
self.vertices[18] = (VertexData){{-0.5, 0.5, 0.5}, {1, 1}};
self.vertices[19] = (VertexData){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[20] = (VertexData){{-0.5, 0.5, -0.5}, {1, 0}};
self.vertices[21] = (VertexData){{-0.5, -0.5, 0.5}, {0, 1}};
self.vertices[22] = (VertexData){{-0.5, 0.5, -0.5}, {1, 0}};
self.vertices[23] = (VertexData){{-0.5, -0.5, -0.5}, {0, 0}};
// 右面
self.vertices[24] = (VertexData){{0.5, 0.5, 0.5}, {1, 1}};
self.vertices[25] = (VertexData){{0.5, -0.5, 0.5}, {0, 1}};
self.vertices[26] = (VertexData){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[27] = (VertexData){{0.5, -0.5, 0.5}, {0, 1}};
self.vertices[28] = (VertexData){{0.5, 0.5, -0.5}, {1, 0}};
self.vertices[29] = (VertexData){{0.5, -0.5, -0.5}, {0, 0}};
// 后面
self.vertices[30] = (VertexData){{-0.5, 0.5, -0.5}, {0, 1}};
self.vertices[31] = (VertexData){{-0.5, -0.5, -0.5}, {0, 0}};
self.vertices[32] = (VertexData){{0.5, 0.5, -0.5}, {1, 1}};
self.vertices[33] = (VertexData){{-0.5, -0.5, -0.5}, {0, 0}};
self.vertices[34] = (VertexData){{0.5, 0.5, -0.5}, {1, 1}};
self.vertices[35] = (VertexData){{0.5, -0.5, -0.5}, {1, 0}};
//3.开辟数据缓存区
glGenBuffers(1, &_vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
GLsizeiptr bufferSize = sizeof(VertexData) * kVertexCount;
glBufferData(GL_ARRAY_BUFFER, bufferSize, self.vertices, GL_STATIC_DRAW);
//4.设置顶点数据读取方式
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), NULL + offsetof(VertexData, vertexCoordinate));
//5.设置纹理坐标读取方式
glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(VertexData), NULL + offsetof(VertexData, textureCoordinate));
}
-(void)addCADisplayLink
{
self.angle = 0;
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
[self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
}
-(void)update
{
//1.计算旋转的度数（度数->弧度）
self.angle = (self.angle + 5) % 360;
//2.修改GLKBaseEffect中模型视图矩阵堆栈
self.baseEffect.transform.modelviewMatrix = GLKMatrix4MakeRotation(GLKMathDegreesToRadians(self.angle), 0.3f, 1.0f, -0.7f);
//3.重新渲染
[self.glkView display];
}
-(void)dealloc
{
//1.设置EAGLContext为nil
if ([EAGLContext currentContext] == self.glkView.context)
{
[EAGLContext setCurrentContext:nil];
}
//2.释放顶点数据
if (_vertices)
{
free(_vertices);
_vertices = nil;
}
//3.删除缓存区
if (_vertexBuffer)
{
glDeleteBuffers(1, &_vertexBuffer);
_vertexBuffer = 0;
}
//4.停止CADisplayLink
[self.displayLink invalidate];
}
#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/深度缓存区
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//3.准备绘制
[self.baseEffect prepareToDraw];
//4.开始绘制
glDrawArrays(GL_TRIANGLES, 0, kVertexCount);
}
@end
旋转立方体.png
以下是程序的思维导图：
思维导图.png
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