#include "framebufferobject.h"

FrameBufferObject::FrameBufferObject()
{
	glGenFramebuffers(1, &mFrameBufferObject);
}
void FrameBufferObject::AttachColorBuffer(const char*bufferName, GLenum attachment, int width, int height) {
	
	//在显存中申请一块空间，并置空
	GLuint colorBuffer;
	glGenTextures(1, &colorBuffer);
	glBindTexture(GL_TEXTURE_2D, colorBuffer);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
	glBindTexture(GL_TEXTURE_2D, 0);

	//把上面申请的空间和frame buffer 绑定
	glBindFramebuffer(GL_FRAMEBUFFER, mFrameBufferObject);
	glFramebufferTexture2D(GL_FRAMEBUFFER, attachment, GL_TEXTURE_2D, colorBuffer, 0);
	glBindFramebuffer(GL_FRAMEBUFFER, 0);

	mDrawBuffers.push_back(attachment);
	mBuffers.insert(std::pair<std::string, GLuint>(bufferName, colorBuffer));
}
void FrameBufferObject::AttachDepthBuffer(const char*bufferName, int width, int height) {
	GLuint depthMap;
	glGenTextures(1, &depthMap);
	glBindTexture(GL_TEXTURE_2D, depthMap);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, width, height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
	glBindTexture(GL_TEXTURE_2D, 0);

	glBindFramebuffer(GL_FRAMEBUFFER, mFrameBufferObject);
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthMap, 0);
	glBindFramebuffer(GL_FRAMEBUFFER, 0);

	mBuffers.insert(std::pair<std::string, GLuint>(bufferName, depthMap));
}
void FrameBufferObject::Finish() {
	int nCount = (int)mDrawBuffers.size();
	if (nCount > 0) {
		GLenum *buffers = new GLenum[nCount];
		int i = 0;
		while (i<nCount) {
			buffers[i] = mDrawBuffers[i];
			i++;
		}
		glBindFramebuffer(GL_FRAMEBUFFER, mFrameBufferObject);
		glDrawBuffers(nCount, buffers);
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
	}
}
void FrameBufferObject::Bind() {
	glGetIntegerv(GL_FRAMEBUFFER_BINDING, &mPrevFrameBuffer);//绑定前记录一下buffer，为解绑返回这个buffer做准备
	glBindFramebuffer(GL_FRAMEBUFFER, mFrameBufferObject);
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}
void FrameBufferObject::Unbind() {
	glBindFramebuffer(GL_FRAMEBUFFER, mPrevFrameBuffer);
}
GLuint FrameBufferObject::GetBuffer(const char*bufferName) {
	auto iter = mBuffers.find(bufferName);
	if (iter != mBuffers.end()) {
		return iter->second;
	}
	return 0;
}