[英]OpenGL ES Render to Texture
我一直无法找到简单的代码来将场景渲染到OpenGL ES中的纹理(特别是对于iPhone,如果这很重要)。 我有兴趣知道以下内容:
这就是我的做法。
我定义了一个纹理变量(我使用Apple的Texture2D
类,但如果需要,可以使用OpenGL纹理id)和帧缓冲区:
Texture2d * texture;
GLuint textureFrameBuffer;
然后在某些时候,我创建纹理,帧缓冲区并附加渲染缓冲区。 这只需要做一次:
texture = [[Texture2D alloc] initWithData:0
pixelFormat:kTexture2DPixelFormat_RGB888
pixelsWide:32
pixelsHigh:32
contentSize:CGSizeMake(width, height)];
// create framebuffer
glGenFramebuffersOES(1, &textureFrameBuffer);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, textureFrameBuffer);
// attach renderbuffer
glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, texture.name, 0);
// unbind frame buffer
glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);
每次我想渲染纹理时,我都会:
glBindFramebufferOES(GL_FRAMEBUFFER_OES, textureFrameBuffer);
...
// GL commands
...
glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);
关于你的问题3,就是这样,你可以使用纹理,就像它是任何其他纹理一样。
要将场景渲染到纹理,必须使用与纹理关联的帧缓冲区。 这是我为简化它而创建的方法:
void glGenTextureFromFramebuffer(GLuint *t, GLuint *f, GLsizei w, GLsizei h)
{
glGenFramebuffers(1, f);
glGenTextures(1, t);
glBindFramebuffer(GL_FRAMEBUFFER, *f);
glBindTexture(GL_TEXTURE_2D, *t);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, *t, 0);
GLuint depthbuffer;
glGenRenderbuffers(1, &depthbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, w, h);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthbuffer);
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if(status != GL_FRAMEBUFFER_COMPLETE)
NSLog(@"Framebuffer status: %x", (int)status);
}
您可以轻松创建帧缓冲区和纹理:
GLuint _texture, _framebuffer;
GLsizei w,h;
float scale = [UIScreen mainScreen].scale;
w = self.view.bounds.size.width * scale;
h = self.view.bounds.size.height * scale;
glGenTextureFromFramebuffer(&_texture, &_framebuffer, w, h);
您可以稍后使用_framebuffer在draw方法中将场景渲染为_texture:
glBindFramebuffer(GL_FRAMEBUFFER, _framebuffer);
//draw here the content you want in the texture
//_texture is now a texture with the drawn content
//bind the base framebuffer
glBindFramebuffer(GL_FRAMEBUFFER, 0);
//or if you use GLKit
[view bindDrawable];
//draw normaly
现在你可以用纹理做你想做的事了。 如果你想做一些后期处理(模糊,绽放,阴影等......)你可以!
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