一、理解
顶点数据存储在申请的缓冲区中，其由数据总线传递给着色器（如果是片元着色器，还须将顶点转换成片元），再由着色器最终渲染到涂层上；
二、思路
1.设置涂层；
2.创建上下文；
3.清空缓存区；
4.创建渲染缓存区和帧缓存区；
5.开始绘制；
三、核心代码
//最终渲染
- (
void)renderLayer
{
//设置窗口背景颜色
glClearColor(
0.0,
0.0,
0.0,
1.0);
//清空颜色缓存
glClear(GL_COLOR_BUFFER_BIT);
//设置视口大小
CGFloat scale =
[[UIScreen mainScreen] scale];
glViewport(self.frame.origin.x*scale, self.frame.origin.y*scale, self.frame.size.width*scale, self.frame.size.height*
scale);
//读取顶点和片元着色器程序
NSString *vertFile = [[NSBundle mainBundle] pathForResource:
@"shaderv" ofType:
@"glsl"];
NSString *fragFile = [[NSBundle mainBundle] pathForResource:
@"shaderf" ofType:
@"glsl"];
NSLog(@"vertFile:%@", vertFile);
NSLog(@"fragFile:%@", fragFile);
//判断myProgram是否存在，存在则清空
if (self.myProgram) {
glDeleteProgram(self.myProgram);
self.myProgram =
0;
}
//加载着色器到myProgram中
self.myProgram =
[self loadShader:vertFile frag:fragFile];
//创建链接
glLinkProgram(self.myProgram);
GLint linkSuccess;
//获取链接状态
glGetProgramiv(self.myProgram, GL_LINK_STATUS, &
linkSuccess);
//判断链接是否成功
if (linkSuccess ==
GL_FALSE) {
//获取失败信息
GLchar message[
256];
glGetProgramInfoLog(self.myProgram, sizeof(message),
0, &message[
0]);
//c字符串转换成oc字符串
NSString *messageString =
[NSString stringWithUTF8String:message];
NSLog(@"error:%@", messageString);
return;
} else {
//使用myProgram
glUseProgram(self.myProgram);
}
//创建绘制索引数组
GLuint indices[] =
{
0,
3,
2,
0,
1,
3,
0,
2,
4,
0,
4,
1,
2,
3,
4,
1,
4,
3
};
//判断顶点缓存区是否为空，为空则申请一个缓存区标志符
if (self.myVertices ==
0) {
glGenBuffers(1, &
_myVertices);
}
//----------处理顶点坐标---------
/*顶点数据
1.前3个坐标值（x、y、z），后3个颜色值（RGB）;
2.有先后顺序，否则绘制形状完全不同
*/
GLfloat attrArr[] =
{
-
0.5f,
0.5f,
0.0f,
1.0f,
0.0f,
1.0f,
//左上
0.5f,
0.5f,
0.0f,
1.0f,
0.0f,
1.0f,
//右上
-
0.5f, -
0.5f,
0.0f,
1.0f,
1.0f,
1.0f,
//左下
0.5f, -
0.5f,
0.0f,
1.0f,
1.0f,
1.0f,
//右下
0.0f,
0.0f,
1.0f,
0.0f,
1.0f,
0.0f,
//顶点
};
//将_myVertices绑定到GL_ARRAY_BUFFER标志符上
glBindBuffer(GL_ARRAY_BUFFER, _myVertices);
//把顶点坐标数据从CPU复制到GPU上
glBufferData(GL_ARRAY_BUFFER,
sizeof(attrArr), attrArr, GL_DYNAMIC_DRAW);
//将顶点坐标数据通过myProgram传递到顶点着色器程序的position
//获取顶点属性入口
GLuint position = glGetAttribLocation(self.myProgram,
"position");
/*传递数据
1.一行6个数据，前3个为坐标，后3个为颜色；
2.NULL开始位置：默认为0，指向数组首地址；
*/
glVertexAttribPointer(position, 3, GL_FLOAT, GL_FALSE,
sizeof(GLfloat)*
6, NULL);
//设置合适的格式从缓存区中读取数据
glEnableVertexAttribArray(position);
//处理顶点颜色数据：传递到顶点着色器的positionColor
GLuint positionColor = glGetAttribLocation(self.myProgram,
"positionColor");
glVertexAttribPointer(positionColor, 3, GL_FLOAT, GL_FALSE,
sizeof(GLfloat)*
6, (
float *)NULL +
3);
glEnableVertexAttribArray(positionColor);
//在myProgram中找到透视投影矩阵和模型视图矩阵
GLuint projectionMatrixSlot = glGetUniformLocation(self.myProgram,
"projectionMatrix");
GLuint modelViewMatrixSlot = glGetUniformLocation(self.myProgram,
"modelViewMatrix");
//创建透视投影矩阵并初始化
float width =
self.frame.size.width;
float height =
self.frame.size.height;
KSMatrix4 _projectionMatrix;
ksMatrixLoadIdentity(&
_projectionMatrix);
float aspect = width/
height;
ksPerspective(&_projectionMatrix,
30.0, aspect,
5.0f,
20.0f);
//设置glsl里面的投影矩阵
glUniformMatrix4fv(projectionMatrixSlot,
1, GL_FALSE, (GLfloat *)&_projectionMatrix.m[
0][
0]);
//开启剔除功能
glEnable(GL_CULL_FACE);
//创建平移矩阵：Z轴平移-10
KSMatrix4 _modelViewMatrix;
ksMatrixLoadIdentity(&
_modelViewMatrix);
ksTranslate(&_modelViewMatrix,
0.0,
0.0, -
10.0);
//创建旋转矩阵
KSMatrix4 _rotationMatrix;
ksMatrixLoadIdentity(&
_rotationMatrix);
ksRotate(&_rotationMatrix, xDegree,
1.0,
0.0,
0.0);
ksRotate(&_rotationMatrix, yDegree,
0.0,
1.0,
0.0);
ksRotate(&_rotationMatrix, zDegree,
0.0,
0.0,
1.0);
//将平移矩阵和旋转矩阵相乘，结果放到模型视图矩阵中
ksMatrixMultiply(&_modelViewMatrix, &_rotationMatrix, &
_modelViewMatrix);
//设置glsl里面的模型视图矩阵
glUniformMatrix4fv(modelViewMatrixSlot,
1, GL_FALSE, (GLfloat *)&_modelViewMatrix.m[
0][
0]);
//设置绘制参数：片元、个数、索引数组
glDrawElements(GL_TRIANGLES,
sizeof(indices)/
sizeof(indices[
0]), GL_UNSIGNED_INT, indices);
//由顶点着色器将缓存区中的数据渲染到显示涂层上
[self.myContext presentRenderbuffer:GL_RENDERBUFFER];
}
四、效果
以上是采用GLSL自定义着色器绘制，下面是采用GLKit框架并添加纹理来绘制
//核心代码
- (
void)renderLayer
{
//顶点数据：前3个坐标（x、y、z），中间三个颜色（RGB），最后2个坐标（纹理）
GLfloat attrArr [] =
{
-
0.5,
0.5,
0.0,
0.0,
0.0,
0.5,
0.0,
1.0,
0.5,
0.5,
0.0,
0.0,
0.5,
0.0,
1.0,
1.0,
-
0.5, -
0.5,
0.0,
0.5,
0.0,
0.0,
0.0,
0.0,
0.5, -
0.5,
0.0,
0.0,
0.0,
0.5,
1.0,
0.0,
0.0,
0.0,
1.0,
1.0,
1.0,
1.0,
0.5,
0.5
};
//绘图索引
GLuint indices[] =
{
0,
3,
2,
0,
1,
3,
0,
2,
4,
0,
4,
1,
2,
3,
4,
1,
4,
3,
};
//顶点个数
self.count =
sizeof(indices)/
sizeof(GLuint);
//顶点数据存入缓存区：CPU->GPU
GLuint buffer;
glGenBuffers(1, &
buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(attrArr), attrArr, GL_STATIC_DRAW);
//索引数据存入缓存区：CPU->GPU
GLuint index;
glGenBuffers(1, &
index);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
//传递顶点数据到着色器指定位置
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE,
sizeof(GLfloat)*
8, NULL);
//顶点颜色数据
glEnableVertexAttribArray(GLKVertexAttribColor);
glVertexAttribPointer(GLKVertexAttribColor, 3, GL_FLOAT, GL_FALSE,
sizeof(GLfloat)*
8, (GLfloat *)NULL +
3);
//顶点纹理数据
glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE,
sizeof(GLfloat)*
8, (GLfloat *)NULL +
6);
//加载纹理
NSString *filePath = [[NSBundle mainBundle] pathForResource:
@"cTest" ofType:
@"jpg"];
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
@"1", GLKTextureLoaderOriginBottomLeft, nil];
GLKTextureInfo *textureInfo =
[GLKTextureLoader textureWithContentsOfFile:filePath options:options error:nil];
self.mEffect =
[[GLKBaseEffect alloc] init];
self.mEffect.texture2d0.enabled =
GL_TRUE;
self.mEffect.texture2d0.name =
textureInfo.name;
//创建透视投影矩阵
CGSize size =
self.view.bounds.size;
float aspect = fabs(size.width/
size.height);
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(
90.0), aspect,
0.1,
10.0);
//设置等比缩放
projectionMatrix = GLKMatrix4Scale(projectionMatrix,
1.0,
1.0,
1.0);
self.mEffect.transform.projectionMatrix =
projectionMatrix;
//设置平移：Z轴负方向平移2.0
GLKMatrix4 modelViewMatrix = GLKMatrix4Translate(GLKMatrix4Identity,
0.0,
0.0, -
2.0);
self.mEffect.transform.modelviewMatrix =
modelViewMatrix;
//设置定时器
double seconds =
0.1;
timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,
0,
0, dispatch_get_main_queue());
dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, seconds*NSEC_PER_SEC,
0);
dispatch_source_set_event_handler(timer, ^
{
self.xDegree +=
0.1*
self.XB;
self.yDegree +=
0.1*
self.YB;
self.zDegree +=
0.1*
self.ZB;
});
dispatch_resume(timer);
}
效果：
GitHub
转载于:https://www.cnblogs.com/lybSkill/p/10069233.html
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