Class encapsulating an OpenGL framebuffer object. More...

#include <framebuffer.hpp>

Public Member Functions
GLuint	name () const
	Retrieve the OpenGL name of this framebuffer. More...

void	bind ()
	Bind this framebuffer to the GL_FRAMEBUFFER target. More...

void	attach_texture (GLenum attachment, GLenum textarget, const texture< GL_TEXTURE_CUBE_MAP > &the_texture, GLint level)
	Attach a non-array cubemap to the given attachment. More...

template<GLenum Target>
void	attach_texture (GLenum attachment, const texture< Target > &the_texture, GLint level)
	Attach a texture to the given attachment. More...

template<GLenum Target>
void	attach_texture_layer (GLenum attachment, const texture< Target > &the_texture, GLint level, GLint layer)
	Attach a texture layer to the given attachment. More...

void	detach_texture (GLenum attachment)
	Clear a texture attachment. More...

void	add_renderbuffer (GLenum attachment, renderbuffer &&the_renderbuffer)
	Attach a renderbuffer to the given attachment. More...

void	remove_renderbuffer (GLenum attachment)
	Clear a renderbuffer attachment. More...

GLenum	status ()
	Check the status of the framebuffer. More...

bool	complete ()
	Check if the framebuffer is complete. More...

Static Public Member Functions
static void	unbind ()
	Unbind the framebuffer currently bound to the GL_FRAMEBUFFER target. More...

Detailed Description

Class encapsulating an OpenGL framebuffer object.

A gls::framebuffer is an object that encapsulates an OpenGL framebuffer object.

Like all objects in GLS, the underlying name is generated at object construction and deleted at destruction. This can be retrieved with name().

WARNING: Unlike other OpenGL objects, framebuffer objects are not shareable between contexts. As such, a gls::framebuffer object is only valid for use within the context where it was constructed. No checks are made to ensure it is used properly. If strange behaviour occurs, be sure to check the reported OpenGL errors in a debug configuration and assure you are not transferring the gls::framebuffer between contexts.

Framebuffer objects are the primary way of rendering to an offscreen surface on hardware that supports it. By default, i.e. when 0 is bound to GL_FRAMEBUFFER all draw commands affect the default framebuffer, typically the back buffer in double buffered applications. To draw to a framebuffer object instead, it has to be bound. All draw commands that are issued while it is bound will affect the framebuffer and its attachments. Once you want to draw to the back buffer once again, simply unbind the framebuffer.

The framebuffer attachments represent surfaces on which draw commands will have an affect. The depth attachment will have depth values written to it while the colour attachments will have colour values written to it and so on. The storage for these attachments comes either from standard texture objects or, since texture objects cannot store non-colour values, renderbuffer objects. The gls::framebuffer object will take ownership of any gls::renderbuffer objects that are attached to it. After all draw commands affecting the framebuffer have completed, one can use the attached texture objects much like one would use any other texture object. Just beware of feedback loops.

After assembling a framebuffer from its attachments and before rendering to it, it is always a good idea to check whether it is complete. This can be done simply by calling complete(). If it is incomplete, calling status() will return the reason for its incompleteness.

To render to a gls::framebuffer, simply call bind(). It will bind the gls::framebuffer to the GL_FRAMEBUFFER binding and replace any previously bound to that target. To clear the GL_FRAMEBUFFER binding and render to the back buffer again, call unbind().

Example usage:

auto texture = gls::texture<GL_TEXTURE_2D>();
texture.image_2d( 0, GL_RGBA, 100, 100, GL_RGBA, GL_FLOAT, nullptr );
auto framebuffer = gls::framebuffer();
framebuffer.attach_texture( GL_COLOR_ATTACHMENT0, texture, 0 );
framebuffer.add_renderbuffer( GL_DEPTH_ATTACHMENT, gls::renderbuffer( GL_DEPTH_COMPONENT24, 100, 100 ) );
if( !framebuffer.complete() ) {
    ... framebuffer is not complete ...
}
framebuffer.bind();
... draw stuff to the framebuffer ...
framebuffer.unbind();

Member Function Documentation

GLuint name ( ) const

Retrieve the OpenGL name of this framebuffer.

Returns: OpenGL name of this framebuffer

void bind ( )

Bind this framebuffer to the GL_FRAMEBUFFER target.

If you want to bind this framebuffer to a target other than GL_FRAMEBUFFER, you can always do this manually with:

glBindFramebuffer( <your target>, framebuffer.name() );

static void unbind ( )

static

Unbind the framebuffer currently bound to the GL_FRAMEBUFFER target.

If you want to unbind a framebuffer that is bound to a target other than GL_FRAMEBUFFER, you can always do this manually with:

glBindFramebuffer( <your target>, 0 );

void attach_texture	(	GLenum	attachment,
		GLenum	textarget,
		const texture< GL_TEXTURE_CUBE_MAP > &	the_texture,
		GLint	level
	)

Attach a non-array cubemap to the given attachment.

Parameters

attachment	Attachment to attach to
textarget	Cubemap texture target (GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, etc.)
the_texture	The cubemap texture to attach
level	Level of the cubemap texture to attach

void attach_texture	(	GLenum	attachment,
		const texture< Target > &	the_texture,
		GLint	level
	)

Attach a texture to the given attachment.

Parameters

attachment	Attachment to attach to
the_texture	The texture to attach
level	Level of the texture to attach

void attach_texture_layer	(	GLenum	attachment,
		const texture< Target > &	the_texture,
		GLint	level,
		GLint	layer
	)

Attach a texture layer to the given attachment.

Parameters

attachment	Attachment to attach to
the_texture	The texture to attach
level	Level of the texture to attach
layer	Layer of the texture to attach

void detach_texture ( GLenum attachment )

Clear a texture attachment.

Parameters

attachment Attachment to detach a texture from

void add_renderbuffer	(	GLenum	attachment,
		renderbuffer &&	the_renderbuffer
	)

Attach a renderbuffer to the given attachment.

Note: This method requires that you transfer ownership (i.e. std::move or equivalent) of the renderbuffer to the framebuffer. It will be destroyed either when the attachment is cleared or the gls::framebuffer is destroyed.

Parameters

attachment	Attachment to attach to
the_renderbuffer	The renderbuffer to attach

void remove_renderbuffer ( GLenum attachment )

Clear a renderbuffer attachment.

Parameters

attachment Attachment to detach a renderbuffer from

GLenum status ( )

Check the status of the framebuffer.

Returns: Status of the framebuffer

bool complete ( )

Check if the framebuffer is complete.

Returns: true if the framebuffer is complete, false otherwise

Public Member Functions

Static Public Member Functions

Detailed Description

Member Function Documentation