OpenGL与OpenGL在移动端的应用

+(Class)layerClass{//默认是CALayer
    //OpenGL内容只会在此类layer上描绘
    return [CAEAGLLayer class];
}

-(void)setupLayerAndContext
{
    _eaglLayer = (CAEAGLLayer *)self.layer;
    _eaglLayer.opaque = YES;
    _eaglLayer.drawableProperties = @{
                                      kEAGLDrawablePropertyRetainedBacking:@(NO),
                                      kEAGLDrawablePropertyColorFormat:kEAGLColorFormatRGBA8
                                      };
    _eaglLayer.contentsScale = screenScale;
    
    // 指定 OpenGLES 渲染API的版本，在这里我们使用OpenGLES 3.0，由于3.0兼容2.0并且功能更强，为何不用更好的呢
    //注：在iOS上，可以支持opengles3.0的最低环境是iphone5s ios7.0.
    _context = [[EAGLContext alloc]initWithAPI:kEAGLRenderingAPIOpenGLES3];
    [EAGLContext setCurrentContext:_context];
    
}

-(void)setupRenderBuffer{
    glGenRenderbuffers(1, &_renderBuffer); //生成和绑定render buffer的API函数
    glBindRenderbuffer(GL_RENDERBUFFER, _renderBuffer);
    //为其分配空间
    [_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:_eaglLayer];
}

-(void)setupFrameBuffer{
    glGenFramebuffers(1, &_frameBuffer);   //生成和绑定frame buffer的API函数
    glBindFramebuffer(GL_FRAMEBUFFER, _frameBuffer);
    //将renderbuffer跟framebuffer进行绑定
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _renderBuffer);
}

-(void)render
{
    //设置清屏颜色,默认是黑色，如果你的运行结果是黑色，问题就可能在这儿
    glClearColor(0.3, 0.5, 0.8, 1.0);
    /*
    glClear指定清除的buffer
    共可设置三个选项GL_COLOR_BUFFER_BIT，GL_DEPTH_BUFFER_BIT和GL_STENCIL_BUFFER_BIT
    也可组合如:glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    这里我们只用了color buffer，所以只需清除GL_COLOR_BUFFER_BIT
     */
    glClear(GL_COLOR_BUFFER_BIT);
    
    [_context presentRenderbuffer:_renderBuffer];
}

    float aspect = self.frame.size.width/self.frame.size.height;
    _projectionMatrix = GLKMatrix4MakePerspective(45.0*M_PI/180.0, aspect, 0.0001, 100);
    glUniformMatrix4fv(_projectionSlot, 1, GL_FALSE, _projectionMatrix.m);

    eyeX = SXYZ * sinf(RZ) * cosf(RX);
    eyeY = SXYZ * sinf(RX);
    eyeZ = SXYZ * cosf(RZ) * cosf(RX);
    
    eyeX += TX;
    eyeY += TY;
    eyeZ += TZ;
    _camaraMatrix = GLKMatrix4MakeLookAt(eyeX, eyeY, eyeZ, TX, TY, TZ, 0, 1, 0);
    glUniformMatrix4fv(_modelViewSlot, 1, GL_FALSE, _camaraMatrix.m);

    _poiTitleModelViewMatrix = GLKMatrix4MakeTranslation(titlePoint.x, poiPlaneTop+0.005, titlePoint.y);
    _poiTitleModelViewMatrix = GLKMatrix4RotateY(_poiTitleModelViewMatrix, RY);
    _poiTitleModelViewMatrix = GLKMatrix4RotateX(_poiTitleModelViewMatrix, -RX);
    camara_position_distance = sqrtf(pow(eyeX-titlePoint.x, 2)+pow(eyeY-(poiPlaneTop+0.005), 2)+pow(eyeZ-titlePoint.y, 2));
    _poiTitleModelViewMatrix = GLKMatrix4Scale(_poiTitleModelViewMatrix, camara_position_distance, camara_position_distance, camara_position_distance);

attribute vec4 Position;

attribute vec2 TexCoordIn;
varying vec2 TexCoordOut;

uniform bool isLocate;
uniform mat4 locateModel;

uniform mat4 Projection;
uniform mat4 View;
uniform mat4 Model;

void main(){
    if (isLocate) {
        gl_Position = Projection * View * locateModel * Position;
    }else {
        gl_Position = Projection * View * Model * Position;
    }
    
//    gl_Position = Position;
    TexCoordOut = vec2(TexCoordIn.x, 1.0-TexCoordIn.y);
}

precision mediump float;

varying mediump vec4 OutColor;
uniform bool is_side;
uniform float sideColor;
uniform bool is_sprite;
void main()
{
    if (is_sprite) {
        if (length(gl_PointCoord-vec2(0.5)) > 0.45)  //0.5会冒出来
            discard;
    }else
    gl_FragColor = OutColor;
    gl_FragColor = vec4(gl_FragColor.r*OutColor.r,gl_FragColor.g*OutColor.g,gl_FragColor.b*OutColor.b,gl_FragColor.a*OutColor.a);
    
    if (is_side) {
//        gl_FragColor = gl_FragColor * vec4(sideColor,sideColor,sideColor,1.0);
        gl_FragColor = gl_FragColor;
    }
}

-(void)render
{
    
    [EAGLContext setCurrentContext:_context];
    glClearColor([backColorArr[0] floatValue], [backColorArr[1] floatValue], [backColorArr[2] floatValue], 1);
    //    glEnable(GL_POLYGON_OFFSET_FILL); //解决z_fighting问题
    //    glPolygonOffset(1.0f, 1.0f);
    
    glEnable(GL_BLEND);  //允许混合
    //    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
    
    //MSAA处理
    glBindFramebuffer(GL_FRAMEBUFFER, mMSAAFramebuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, mMSAARenderbuffer);
    
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    glViewport(0, 0, self.frame.size.width*2, self.frame.size.height*2);
    
    [self updateCubeCenterToScreenPoint];  //确定边界
    
    glUseProgram(_programHandle);  //使用某个这色器程序
    
    [self setupCubeProjectionAndCamara];
    [self drawOutLine]; //画轮廓
    [self drawTopPoi];  //画顶层poi  里面有多次深度测试的开启和关闭
    
    
    glDisable(GL_DEPTH_TEST);  //关闭深度测试
    
    if (naviPathArr.count) {
        for (int i=0; i<naviPathArr.count; i++) {
            NSArray *onePath = naviPathArr[i];
            [self drawNaviRoute:onePath];  //画路径和箭头
            [self drawNaviArrow:onePath];
        }
    }
    [self drawNormalOverlays]; //绘制覆盖物
    
    glBlendFuncSeparate(GL_ONE, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA); //避免文字穿透
    glUseProgram(_poiTitleProgramHandle);
    [self setupTitleProjectionAndCamara];
    if (isFirstDrawTile) {//如果第一次筛选，不是第一次的筛选都在手势里处理了
        [self setupTitlesAndFacilyties];    //筛选文字和图例
        isFirstDrawTile = NO;
    }
    [self drawTopPoiTexture]; //画顶面贴图
    [self drawFacilities]; //画图例
    [self drawPoiTitles];  //画文字
    [self drawTextureOverlays]; //画纹理型覆盖物
    
    if (isLocate) {//若需要画定位点
        [self drawLocatePoint:locatePoint];
    }
    
    glUseProgram(_heatMapProgramHandle);  //绘制热力图使用热力图的这色器程序
    [self setupHeatMapProjectionAndCamara];
    [self drawHeatMap];    //画热力图
    
    //MSAA处理
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, frameBuffer);
    glBindFramebuffer(GL_READ_FRAMEBUFFER, mMSAAFramebuffer);
    
    glInvalidateFramebuffer(GL_READ_FRAMEBUFFER, 1, (GLenum[]){GL_DEPTH_ATTACHMENT});
    glBlitFramebuffer(0, 0, _width, _height, 0, 0, _width, _height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
    
    glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);

    [_context presentRenderbuffer:GL_RENDERBUFFER];//调用这句话，图形才能渲染到屏幕上
    
}

        [self setupLayer];
        [self setupContext];
        
        [self setupDepthBuffer];  
        [self setupRenderBuffer];
        [self setupFrameBuffer];

        [self setupProgram];  //配置program
        
        [self setupProjectionMatrix];
        [self setupModelViewMatrix];

        [self setupRenderData];
        [self render];