Framebuffer Class Reference

#include <ImFusion/Core/GL/Framebuffer.h>

Wrapper class for OpenGL Framebuffer Objects (FBO). More...

Inheritance diagram for Framebuffer:

Detailed Description

Wrapper class for OpenGL Framebuffer Objects (FBO).

FBOs allow for using custom textures as framebuffer attachments so that you can render to them instead of rendering to the main screen.

To avoid confusion, GL::Framebuffer will synchronize the color attachment point Attachment::ColorI with the fragment color location (location in glDrawBuffers() array/fragment shader outputs). Thus, color attachment i will always end up on draw buffer/fragment shader output location i.

Example for rendering to texture:

GL::Texture colorTex1, colorTex2, depthTex = ...;
GL::Framebuffer fbo;
auto guard = fbo.guardedBind();
fbo.attach(colorTex1, GL::Framebuffer::Attachment::Color0);
fbo.attach(colorTex2, GL::Framebuffer::Attachment::Color2);
fbo.attach(depthTex, GL::Framebuffer::Attachment::Depth);
fbo.setDrawBuffers();
 
// perform rendering
// rendering output will be routed into the attached textures colorTex1, colorTex2, and depthTex

the corresponding shader should be setup like this:

layout (location = 0) out vec4 out_color0;   // output variable for color attachment 0
layout (location = 2) out vec4 out_color2;   // output variable for color attachment 2
 
void main() {
    // write to outputs
    out_color0 = ...;
    out_color2 = ...;
    gl_FragDepth = ...;
}

Note

The bound FBO is a global state of the current OpenGL context and only one FBO can be bound at any time. Therefore, make sure to use state guards when binding your FBO. Furthermore, FBOs can not be shared across OpenGL contexts.

See also

• https://www.khronos.org/opengl/wiki/Framebuffer_Object
• https://www.khronos.org/opengl/wiki/Fragment_Shader#Output_buffers

Public Types
enum class	Attachment {   Color0 = 0x8CE0 , Color1 = 0x8CE1 , Color2 = 0x8CE2 , Color3 = 0x8CE3 ,   Color4 = 0x8CE4 , Color5 = 0x8CE5 , Color6 = 0x8CE6 , Color7 = 0x8CE7 ,   Depth = 0x8D00 , Stencil = 0x8D20 , DepthStencil = 0x821A }
	Enumeration of possible FBO attachment points. More...

Public Member Functions
	Framebuffer ()
	Construct a new FBO.
	~Framebuffer ()
	Destroy FBO.
void	bind ()
	Bind FBO.
void	unbind ()
	Unbind FBO, resets the bound FBO to 0.
bool	isBound () const
	Returns true if this framebuffer object is the current draw buffer.
StateGuard	guardedBind ()
	Binds the FBO and returns a GlStateGuard to restore the FBO binding state before the call.
void	attach (Texture &texture, Attachment attachment, int mipmapLevel=0)
	Attach the given texture as a whole to this FBO.
void	attachLayer (Texture &texture, Attachment attachment, int layer, int mipmapLevel=0)
	Attach a single layer/slice of the given texture to this FBO.
void	attach (Texture &texture, int position=0)
	Convenience overload that auto-determines the position based on the texture's internal format.
void	detach (Attachment attachment)
	Detaches the texture at the given attachment point.
void	detachAll ()
	Detaches all previously attached textures.
void	setDrawBuffers ()
	Set draw buffers according to the attached color textures.
void	clearDrawBuffers ()
	Clear draw buffers.
uint32_t	id () const
	Return the OpenGL name/id for the wrapped FBO.

Static Public Member Functions
static bool	isComplete ()
	Check FBO status, will log the reason in case of errors and return false.

Member Enumeration Documentation

Attachment

enum class Attachment

strong

Enumeration of possible FBO attachment points.

See also

https://www.khronos.org/opengl/wiki/Framebuffer_Object#Framebuffer_Object_Structure

Enumerator
Color0	Color attachment of fragment shader output location 0.
Color1	Color attachment of fragment shader output location 1.
Color2	Color attachment of fragment shader output location 2.
Color3	Color attachment of fragment shader output location 3.
Color4	Color attachment of fragment shader output location 4.
Color5	Color attachment of fragment shader output location 5.
Color6	Color attachment of fragment shader output location 6.
Color7	Color attachment of fragment shader output location 7.
Depth	Depth buffer attachment, texture must have depth format.
Stencil	Stencil buffer attachment, texture must have stencil format.
DepthStencil	Combined depth-stencil buffer attachment, texture must have depth-stencil format.

Constructor & Destructor Documentation

Framebuffer()

Framebuffer

(

)

Construct a new FBO.

Exceptions

std::runtime_error

if the corresponding OpenGL framebuffer object could not be created.

Member Function Documentation

unbind()

void unbind

(

)

Unbind FBO, resets the bound FBO to 0.

Note

It is not encouraged to use unbind() unless you're absolutely sure that the surrounding code expects the bound FBO to be 0. If you're unsure what FBO state the surrounding code requires, use guardedBind() instead of combining bind() and unbind() or manage your own GlStateGuard explicitly.

guardedBind()

StateGuard guardedBind ( )

nodiscard

Binds the FBO and returns a GlStateGuard to restore the FBO binding state before the call.

Note

Make sure to capture the returned variable, otherwise the call will have no effect.

In case of recurrent binding of FBOs in tight loops, consider managing a single GlStateGuard outside the loop and bind the FBO using bind().

attach() [1/2]

void attach	(	Texture &	texture,
		Attachment	attachment,
		int	mipmapLevel = 0 )

Attach the given texture as a whole to this FBO.

Note

FBO must be bound prior to calling this function.

Parameters

texture	Texture to attach
attachment	Attachment point
mipmapLevel	Mipmap level of texture to attach

attachLayer()

void attachLayer	(	Texture &	texture,
		Attachment	attachment,
		int	layer,
		int	mipmapLevel = 0 )

Attach a single layer/slice of the given texture to this FBO.

Note

FBO must be bound prior to calling this function.

Parameters

texture	Texture to attach, must be a 3D texture or an array texture.
attachment	Attachment point
layer	Layer/slice of texture to attach
mipmapLevel	Mipmap level of texture to attach

attach() [2/2]

void attach	(	Texture &	texture,
		int	position = 0 )

Convenience overload that auto-determines the position based on the texture's internal format.

Note

FBO must be bound prior to calling this function.

Parameters

texture	Texture to attach
position	Ignored if texture has a depth or stencil format. Otherwise describes the index of the color attachment, i.e. attachment = (Color0 + position).

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The documentation for this class was generated from the following file:

• ImFusion/Core/GL/Framebuffer.h