GLKit 实现光照

新建一个 xcode 项目，在 ViewController.h 文件导入 <GLKit/GLKit.h> 并继承 GLKViewController，Main.storyboard 中把 View 的父类改为 GLKView，然后在 ViewController.m 实现代码。
根据下图绘制金字塔并实现光照
1.png
ViewController.m 代码如下
#import "ViewController.h"

//顶点数据结构
typedef struct {
    GLKVector3 position; //顶点向量
    GLKVector3 normal; //法线向量
}SceneVertex;

@interface ViewController ()

@property(nonatomic,strong)EAGLContext * myContext;
@property(nonatomic,strong)GLKBaseEffect * baseEffect;

@end

@implementation ViewController


- (void)viewDidLoad
{
    [super viewDidLoad];
   
    //新建OpenGL ES 上下文
    EAGLContext * context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];
   
    //设置GLKView
    GLKView * glkView = (GLKView *)self.view;
    glkView.context = context;
    glkView.drawableColorFormat = GLKViewDrawableColorFormatRGBA8888;
    glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    
    [EAGLContext setCurrentContext:context];
    
    
    //1.金字塔Effect
    self.baseEffect = [[GLKBaseEffect alloc] init];
    self.baseEffect.constantColor = GLKVector4Make(0.1f, 0.2f, 0.3f, 1.0f);
    self.baseEffect.light0.enabled = GL_TRUE;
    
    //光的漫射部分 GLKVector4Make(R,G,B,A)
    self.baseEffect.light0.diffuseColor = GLKVector4Make(0.7f, 0.7f, 0.7f, 1.0f);
    //世界坐标中的光的位置
    self.baseEffect.light0.position = GLKVector4Make(1.0f, 1.0f, 0.5f, 0.0f);
    
    //3.调整模型矩阵，更好的观察
    //可以尝试不执行这段代码，改为false
    if (true)
    {
        //围绕x轴旋转-60度
        //返回一个4x4矩阵进行绕任意矢量旋转
        GLKMatrix4 modelViewMatrix = GLKMatrix4MakeRotation(GLKMathDegreesToRadians(-60.0f), 1.0f, 0.0f, 0.0f);
        
        //围绕z轴，旋转-30度
        modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, GLKMathDegreesToRadians(-30.0f), 0.0f, 0.0f, 1.0f);
        
        //围绕Z方向，移动0.25f
        modelViewMatrix = GLKMatrix4Translate(modelViewMatrix, 0.0f, 0.0f, 0.25f);
        
        //设置baseEffect模型矩阵
        self.baseEffect.transform.modelviewMatrix = modelViewMatrix;
    }
    
    //设置顶点
    GLKVector3  vertexA = {-0.5,  0.5, -0.5};
    GLKVector3  vertexB = {-0.5,  0.0, -0.5};
    GLKVector3  vertexC = {-0.5, -0.5, -0.5};

    GLKVector3  vertexD = { 0.0,  0.5, -0.5};
    GLKVector3  vertexE = { 0.0,  0.0, 0.0};
    GLKVector3  vertexF = { 0.0, -0.5, -0.5};

    GLKVector3  vertexG = { 0.5,  0.5, -0.5};
    GLKVector3  vertexH = { 0.5,  0.0, -0.5};
    GLKVector3  vertexI = { 0.5, -0.5, -0.5};
    
    SceneVertex vertices[24];
    
    //求出平面法向量
    vertices[0] = (SceneVertex){vertexA,SceneTriangleFaceNormal(vertexA, vertexB,vertexD)};
    vertices[1] = (SceneVertex){vertexB,SceneTriangleFaceNormal(vertexA, vertexB,vertexD)};
    vertices[2] = (SceneVertex){vertexD,SceneTriangleFaceNormal(vertexA, vertexB,vertexD)};
    
    vertices[3] = (SceneVertex){vertexB,SceneTriangleFaceNormal(vertexB, vertexC,vertexF)};
    vertices[4] = (SceneVertex){vertexC,SceneTriangleFaceNormal(vertexB, vertexC,vertexF)};
    vertices[5] = (SceneVertex){vertexF,SceneTriangleFaceNormal(vertexB, vertexC,vertexF)};
    
    vertices[6] = (SceneVertex){vertexD,SceneTriangleFaceNormal(vertexD, vertexB,vertexE)};
    vertices[7] = (SceneVertex){vertexB,SceneTriangleFaceNormal(vertexD, vertexB,vertexE)};
    vertices[8] = (SceneVertex){vertexE,SceneTriangleFaceNormal(vertexD, vertexB,vertexE)};
    
    vertices[9] = (SceneVertex){vertexE,SceneTriangleFaceNormal(vertexE, vertexB,vertexF)};
    vertices[10] = (SceneVertex){vertexB,SceneTriangleFaceNormal(vertexE, vertexB,vertexF)};
    vertices[11] = (SceneVertex){vertexF,SceneTriangleFaceNormal(vertexE, vertexB,vertexF)};
    
    vertices[12] = (SceneVertex){vertexD,SceneTriangleFaceNormal(vertexD, vertexE,vertexH)};
    vertices[13] = (SceneVertex){vertexE,SceneTriangleFaceNormal(vertexD, vertexE,vertexH)};
    vertices[14] = (SceneVertex){vertexH,SceneTriangleFaceNormal(vertexD, vertexE,vertexH)};
    
    vertices[15] = (SceneVertex){vertexE,SceneTriangleFaceNormal(vertexE, vertexF,vertexH)};
    vertices[16] = (SceneVertex){vertexF,SceneTriangleFaceNormal(vertexE, vertexF,vertexH)};
    vertices[17] = (SceneVertex){vertexH,SceneTriangleFaceNormal(vertexE, vertexF,vertexH)};
    
    vertices[18] = (SceneVertex){vertexG,SceneTriangleFaceNormal(vertexG, vertexD,vertexH)};
    vertices[19] = (SceneVertex){vertexD,SceneTriangleFaceNormal(vertexG, vertexD,vertexH)};
    vertices[20] = (SceneVertex){vertexH,SceneTriangleFaceNormal(vertexG, vertexD,vertexH)};
    
    vertices[21] = (SceneVertex){vertexH,SceneTriangleFaceNormal(vertexH, vertexF,vertexI)};
    vertices[22] = (SceneVertex){vertexF,SceneTriangleFaceNormal(vertexH, vertexF,vertexI)};
    vertices[23] = (SceneVertex){vertexI,SceneTriangleFaceNormal(vertexH, vertexF,vertexI)};
    
    //开辟缓存区
    GLuint vertexBuffer;
    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(SceneVertex) * 24, vertices, GL_DYNAMIC_DRAW);
    
    //准备绘制顶点数据
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(SceneVertex), NULL + offsetof(SceneVertex, position));
    
    //准备绘制光照数据
    glEnableVertexAttribArray(GLKVertexAttribNormal);
    glVertexAttribPointer(GLKVertexAttribNormal, 3, GL_FLOAT, GL_FALSE, sizeof(SceneVertex), NULL + offsetof(SceneVertex, normal));
}


#pragma mark - 根据顶点求出法向量
GLKVector3 SceneTriangleFaceNormal(GLKVector3 a,GLKVector3 b,GLKVector3 c)
{
    //vectorA =  b - a
    GLKVector3 vectorA = GLKVector3Subtract(b,a);
    //vectorB =  c - a
    GLKVector3 vectorB = GLKVector3Subtract(c,a);
    //通过 向量A和向量B的叉积求出平面法向量，单元化后返回
    return GLKVector3Normalize(GLKVector3CrossProduct(vectorA, vectorB));
}


#pragma mark - GLKView DrawRect
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
    glClearColor(0.3f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    
    [self.baseEffect prepareToDraw];
    
    glDrawArrays(GL_TRIANGLES, 0, 24);
}


@end
运行效果如下
光照.png