OpenGL ES _ 入门练习_004

-(void)createEAGContext{
self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
if (!self.context) {
NSLog(@"手机不支持opengl es2");
}
[EAGLContext setCurrentContext:self.context]; // 设置为当前上下文
}
// MARK: - 配置view

-(void) configure{
GLKView *view = (GLKView *)self.view;
view.context = self.context;
view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
}
// MARK: - 第二步: 创建GLKBaseEffect 对象

-(void)createBaseEffect{
self.effect = [[GLKBaseEffect alloc] init];
self.effect.light0.enabled = GL_TRUE;
self.effect.light0.diffuseColor = GLKVector4Make(0.5f, 0.1f, 0.4f, 1.0f);
}
// MARK: - 第三步:

- (void)addVertexAndNormal{
glEnable(GL_DEPTH_TEST); // 开启深度测试 让被挡住的像素隐藏
// 讲顶点数据和法线数据加载到GUP 中去
glGenBuffers(1, &_vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(gCubeVertexData), gCubeVertexData, GL_STATIC_DRAW);
// 开启绘制命令 GLKVertexAttribPosition(位置)
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 24, 0);
// 开启绘制命令 GLKVertexAttribPosition(法线)
glEnableVertexAttribArray(GLKVertexAttribNormal);
glVertexAttribPointer(GLKVertexAttribNormal, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(12));
}
// MARK: - 第四步: 清屏

- (void)clearScreen{
glClearColor(0.65f, 0.65f, 0.65f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}
// MARK: - 第五步: 绘制

- (void)draw{
[self.effect prepareToDraw];
glDrawArrays(GL_TRIANGLES, 0, 36);
}
// MARK: - 第六步: 改变运动轨迹

- (void)changeMoveTrack{
// 获取一个屏幕比例值
float aspect = fabs(self.view.bounds.size.width / self.view.bounds.size.height);
//  GLKMatrix4MakePerspective(float fovyRadians, float aspect, float nearZ, float farZ)
/*
* 透视转换
*/
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f);
self.effect.transform.projectionMatrix = projectionMatrix;
GLKMatrix4 baseModelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -10.0f);
baseModelViewMatrix = GLKMatrix4Rotate(baseModelViewMatrix, _rotation, 0.0f, 1.0f, 0.0f);
// 计算自身的坐标和旋转状态
GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.5f);
modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, _rotation, 1.0f, 1.0f, 1.0f);
modelViewMatrix = GLKMatrix4Multiply(baseModelViewMatrix, modelViewMatrix);
self.effect.transform.modelviewMatrix = modelViewMatrix;
_rotation += self.timeSinceLastUpdate * 0.5f;
}
// MARK: - 第七步: 清除工作

- (void)tearDownGL
{
[EAGLContext setCurrentContext:self.context];
glDeleteBuffers(1, &_vertexBuffer);
self.effect = nil;
}
以上几个步骤讲解完毕，最重要的代码来了！
- (void)viewDidLoad

{
[super viewDidLoad];
[self createEAGContext];// 1. 创建管理上下文
[self configure]; // 2.配置
[self createBaseEffect]; // 3.创建渲染管理
[self addVertexAndNormal]; // 4.添加顶点坐标和法线坐标
}
#pragma mark - GLKView and GLKViewController delegate methods
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
[self clearScreen]; // 5.清理屏幕
[self draw]; //.6 绘制
}
- (void)update
{
[self changeMoveTrack]; // 7.移动
}
- (void)dealloc
{
[self tearDownGL]; // 8.清理工作
if ([EAGLContext currentContext] == self.context) {
[EAGLContext setCurrentContext:nil];
}
}