Creating a Render to Texture Secondary Framebuffer for iOS OpenGL ES 2

MyDualFramebufferView.cpp

GLsizei cxFBO;
GLsizei cyFBO;
GLuint _frameBufferID;
GLuint _colorRenderBuffer;
GLuint _depthRenderBuffer;
GLuint _fboTextureID;

void MyDualFramebufferView::Resize(GLfloat width, GLfloat height, GLfloat scale)
{
	_scale = scale;
	_aspect = (GLfloat) width / height;
	_screen = Vec2 (width, height);  // Vec2 is actually a glm::vec2
	cxFBO=_screen.x * scale;
	cyFBO=_screen.y * scale;

	CreateRenderToTextureFBO();
}

void MyDualFramebufferView::CreateRenderToTextureFBO()
{
	if (_frameBufferID != 0)
	{
		glDeleteRenderbuffers(1, &_depthRenderBuffer);
		glDeleteRenderbuffers(1, &_colorRenderBuffer);
		glDeleteFramebuffers(1, &_frameBufferID);
		cout << "Recreating FBO" << endl;
	}

	GLint maxTextureSize;
	glGetIntegerv(GL_MAX_TEXTURE_SIZE, &maxTextureSize);

	if ((cxFBO > maxTextureSize) ||
	    (cyFBO > maxTextureSize))
	{
		throw "Requested size of frame buffer exceeds maximum";
	}

	glGenFramebuffers(1, &_frameBufferID);
	glGenRenderbuffers(1, &_depthRenderBuffer);
	glGenTextures(1, &_fboTextureID);


	// texture
	glBindTexture(GL_TEXTURE_2D, _fboTextureID);
	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_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, cxFBO, cyFBO, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);

	// depth buffer
	glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderBuffer);
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, cxFBO, cyFBO);

	// frame buffer
	glBindFramebuffer(GL_FRAMEBUFFER, _frameBufferID);


	// attachments
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _fboTextureID, 0);
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderBuffer);

	glBindFramebuffer(GL_FRAMEBUFFER, _frameBufferID);
	GLenum status=glCheckFramebufferStatus(GL_FRAMEBUFFER);
	if (status != GL_FRAMEBUFFER_COMPLETE)
	{
		throw "Framebuffer is not complete";
	}

	glBindTexture(GL_TEXTURE_2D, 0);
	glBindFramebuffer(GL_FRAMEBUFFER, 0);
}