OpenGLES_实战04_教你绘制球体

GLKView *glkView = (GLKView*)self.view;
glkView.drawableDepthFormat = GLKViewDrawableDepthFormat24;// 设置深度缓冲区格式
// 创建管理上下文
glkView.context = [[EAGLContext alloc]initWithAPI:kEAGLRenderingAPIOpenGLES2];
// 设置当前上下文
[EAGLContext setCurrentContext:glkView.context];

@property(nonatomic,strong)GLKBaseEffect *baseEffect;
self.baseEffect = [[GLKBaseEffect alloc]init];

#define ES_PI  (3.14159265f)

int generateSphere(int numSlices, float radius, float **vertices,
            float **texCoords, uint16_t **indices, int *numVertices_out) {
int i;
int j;
int numParallels = numSlices / 2;
int numVertices = (numParallels + 1) * (numSlices + 1);
int numIndices = numParallels * numSlices * 6;
float angleStep = (2.0f * ES_PI) / ((float) numSlices);
if (vertices != NULL)
    *vertices = malloc(sizeof(float) * 3 * numVertices);
if (texCoords != NULL)
    *texCoords = malloc(sizeof(float) * 2 * numVertices);
if (indices != NULL)
    *indices = malloc(sizeof(uint16_t) * numIndices);
for (int i = 0; i < numParallels + 1; i++) {
    for (int j = 0; j < numSlices + 1; j++) {
        int vertex = (i * (numSlices + 1) + j) * 3;
        if (vertices) {
            (*vertices)[vertex + 0] = radius * sinf(angleStep * (float)i) *
            sinf(angleStep * (float)j);
            (*vertices)[vertex + 1] = radius * cosf(angleStep * (float)i);
            (*vertices)[vertex + 2] = radius * sinf(angleStep * (float)i) *
            cosf(angleStep * (float)j);
        }
        if (texCoords) {
            int texIndex = (i * (numSlices + 1) + j) * 2;
            (*texCoords)[texIndex + 0] = (float)j / (float)numSlices;
            (*texCoords)[texIndex + 1] = 1.0f - ((float)i / (float)numParallels);
        }
    }
}
if (indices != NULL) {
    uint16_t *indexBuf = (*indices);
    for (i = 0; i < numParallels ; i++) {
        for (j = 0; j < numSlices; j++) {
            *indexBuf++ = i * (numSlices + 1) + j;
            *indexBuf++ = (i + 1) * (numSlices + 1) + j;
            *indexBuf++ = (i + 1) * (numSlices + 1) + (j + 1);
            
            *indexBuf++ = i * (numSlices + 1) + j;
            *indexBuf++ = (i + 1) * (numSlices + 1) + (j + 1);
            *indexBuf++ = i * (numSlices + 1) + (j + 1);
        }
    }
}
if (numVertices_out) {
    *numVertices_out = numVertices;
}
return numIndices;
}

GLfloat   *_vertexData; // 顶点数据
GLfloat   *_texCoords;  // 纹理坐标
GLushort  *_indices;    // 顶点索引
 GLint    _numVetex;   // 顶点数量
GLuint  _texCoordsBuffer;// 纹理坐标内存标识
GLuint  _numIndices; // 顶点索引的数量

 _numIndices = generateSphere(200, 1.0, &(_vertexData), &(_texCoords), &_indices, &_numVetex);

-(void)loadVertexData{

// 加载顶点坐标数据
glGenBuffers(1, &_vertexBuffer); // 申请内存
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer); // 将命名的缓冲对象绑定到指定的类型上去
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*_numVetex*3,_vertexData, GL_STATIC_DRAW);
glEnableVertexAttribArray(GLKVertexAttribPosition);  // 绑定到位置上
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 3*sizeof(GLfloat), NULL);

// 加载顶点索引数据
GLuint _indexBuffer;
glGenBuffers(1, &_indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, _numIndices*sizeof(GLushort), _indices, GL_STATIC_DRAW);



// 加载纹理坐标
glGenBuffers(1, &_texCoordsBuffer);
glBindBuffer(GL_ARRAY_BUFFER, _texCoordsBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*_numVetex*2, _texCoords, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, 2*sizeof(GLfloat), NULL);

}

GLKTextureInfo *textureInfo =
[GLKTextureLoader textureWithCGImage:[UIImage imageNamed:@"earth-diffuse.jpg"].CGImage options:nil error:nil];
self.baseEffect.texture2d0.target = textureInfo.target;
self.baseEffect.texture2d0.name = textureInfo.name;

 // 设置世界坐标和视角
float aspect = fabs(self.view.bounds.size.width / self.view.bounds.size.height);
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f);
self.baseEffect.transform.projectionMatrix = projectionMatrix;

// 设置模型坐标
GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, -1.0f, -6.5f);
self.baseEffect.transform.modelviewMatrix =  modelViewMatrix;

// update方法系统会自动调动  
-(void)update{
 self.baseEffect.transform.modelviewMatrix = GLKMatrix4Rotate(self.baseEffect.transform.modelviewMatrix, 0.1, 0, 1, 0);
}

-(void)glkView:(GLKView *)view drawInRect:(CGRect)rect{

// 清除颜色缓冲区
glClearColor(1.0, 0, 1.0, 1);
glClear(GL_COLOR_BUFFER_BIT);

// 绘制之前必须调用这个方法
[self.baseEffect prepareToDraw];
static int i =1;
if (i < _numIndices-2000){
    i = i+1000;
}else{
    i = _numIndices;
}

// 以画单独三角形的方式 开始绘制
glDrawElements(GL_TRIANGLES, i,GL_UNSIGNED_SHORT, NULL);
}