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Cogl Reference Manual | ![]() |
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Top | Description |
Offscreen BuffersOffscreen Buffers — Functions for creating and manipulating offscreen framebuffers. |
CoglOffscreen * cogl_offscreen_new_to_texture ();
CoglTexture *textureCoglBool cogl_is_offscreen ();
void *objectvoid cogl_set_framebuffer ();
CoglFramebuffer *buffervoid cogl_push_framebuffer ();
CoglFramebuffer *buffervoid cogl_pop_framebuffer (void
);void cogl_set_draw_buffer (CoglBufferTarget target
,CoglHandle offscreen
);void cogl_push_draw_buffer ();
CoglOffscreen * cogl_offscreen_new_to_texture ();
CoglTexture *texture
This creates an offscreen buffer object using the given texture
as the
primary color buffer. It doesn't just initialize the contents of the
offscreen buffer with the texture
; they are tightly bound so that
drawing to the offscreen buffer effectivly updates the contents of the
given texture. You don't need to destroy the offscreen buffer before
you can use the texture
again.
|
A |
Returns : |
a newly instantiated NULL |
CoglBool cogl_is_offscreen ();
void *object
Determines whether the given CoglObject references an offscreen framebuffer object.
|
A pointer to a CoglObject |
Returns : |
TRUE object is a FALSE |
void cogl_set_framebuffer ();
CoglFramebuffer *buffer
This redirects all subsequent drawing to the specified framebuffer. This can
either be an offscreen buffer created with cogl_offscreen_new_to_texture()
or in the future it may be an onscreen framebuffers too.
|
A |
Since 1.2
void cogl_push_framebuffer ();
CoglFramebuffer *buffer
Redirects all subsequent drawing to the specified framebuffer. This can
either be an offscreen buffer created with cogl_offscreen_new_to_texture()
or in the future it may be an onscreen framebuffer too.
You should understand that a framebuffer owns the following state:
So these items will automatically be saved and restored when you push and pop between different framebuffers.
Also remember a newly allocated framebuffer will have an identity matrix for the projection and modelview matrices which gives you a coordinate space like OpenGL with (-1, -1) corresponding to the top left of the viewport, (1, 1) corresponding to the bottom right and +z coming out towards the viewer.
If you want to set up a coordinate space like Clutter does with (0, 0) corresponding to the top left and (framebuffer_width, framebuffer_height) corresponding to the bottom right you can do so like this:
static void setup_viewport (unsigned int width, unsigned int height, float fovy, float aspect, float z_near, float z_far) { float z_camera; CoglMatrix projection_matrix; CoglMatrix mv_matrix; cogl_set_viewport (0, 0, width, height); cogl_perspective (fovy, aspect, z_near, z_far); cogl_get_projection_matrix (&projection_matrix); z_camera = 0.5 * projection_matrix.xx; cogl_matrix_init_identity (&mv_matrix); cogl_matrix_translate (&mv_matrix, -0.5f, -0.5f, -z_camera); cogl_matrix_scale (&mv_matrix, 1.0f / width, -1.0f / height, 1.0f / width); cogl_matrix_translate (&mv_matrix, 0.0f, -1.0 * height, 0.0f); cogl_set_modelview_matrix (&mv_matrix); } static void my_init_framebuffer (ClutterStage *stage, CoglFramebuffer *framebuffer, unsigned int framebuffer_width, unsigned int framebuffer_height) { ClutterPerspective perspective; clutter_stage_get_perspective (stage, &perspective); cogl_push_framebuffer (framebuffer); setup_viewport (framebuffer_width, framebuffer_height, perspective.fovy, perspective.aspect, perspective.z_near, perspective.z_far); }
The previous framebuffer can be restored by calling cogl_pop_framebuffer()
|
A |
Since 1.2
void cogl_pop_framebuffer (void
);
Restores the framebuffer that was previously at the top of the stack. All subsequent drawing will be redirected to this framebuffer.
Since 1.2
void cogl_set_draw_buffer (CoglBufferTarget target
,CoglHandle offscreen
);
cogl_set_draw_buffer
has been deprecated since version 1.2 and should not be used in newly-written code. The target argument was redundant since we could look at
the type of CoglHandle given instead.
Redirects all subsequent drawing to the specified framebuffer. This
can either be an offscreen buffer created with
cogl_offscreen_new_to_texture()
or you can revert to your original
on screen window buffer.
|
A CoglBufferTarget that specifies what kind of framebuffer you are setting as the render target. |
|
If you are setting a framebuffer of type COGL_OFFSCREEN_BUFFER then this is a CoglHandle for the offscreen buffer. |
void cogl_push_draw_buffer ();
cogl_push_draw_buffer
has been deprecated since version 1.2 and should not be used in newly-written code. The draw buffer API was replaced with a framebuffer API
Save cogl_set_draw_buffer()
state.