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Rectangle textures (non-normalized coordinates)Rectangle textures (non-normalized coordinates) — Functions for creating and manipulating rectangle textures for use with non-normalized coordinates. |
Description
These functions allow low-level "rectangle" textures to be allocated.
These textures are never constrained to power-of-two sizes but they
also don't support having a mipmap and can only be wrapped with
COGL_PIPELINE_WRAP_MODE_CLAMP_TO_EDGE
.
The most notable difference between rectangle textures and 2D textures is that rectangle textures are sampled using un-normalized texture coordinates, so instead of using coordinates (0,0) and (1,1) to map to the top-left and bottom right corners of the texture you would instead use (0,0) and (width,height).
The use of non-normalized coordinates can be particularly convenient when writing glsl shaders that use a texture as a lookup table since you don't need to upload separate uniforms to map normalized coordinates to texels.
If you want to sample from a rectangle texture from GLSL you should use the sampler2DRect sampler type.
Applications wanting to use CoglTextureRectangle should first check
for the COGL_FEATURE_ID_TEXTURE_RECTANGLE
feature using
cogl_has_feature()
.
Functions
cogl_texture_rectangle_new_with_size ()
CoglTextureRectangle * cogl_texture_rectangle_new_with_size (CoglContext *ctx
,int width
,int height
);
Creates a new CoglTextureRectangle texture with a given width
,
and height
. This texture is a low-level texture that the GPU can
sample from directly unlike high-level textures such as
CoglTexture2DSliced and CoglAtlasTexture.
width
, height
) where width
and height
are the width and height of the texture.COGL_FEATURE_ID_TEXTURE_RECTANGLE
feature
using cogl_has_feature()
.The storage for the texture is not allocated before this function
returns. You can call cogl_texture_allocate()
to explicitly
allocate the underlying storage or preferably let Cogl
automatically allocate storage lazily when it may know more about
how the texture is going to be used and can optimize how it is
allocated.
Returns value: (transfer full): A pointer to a new CoglTextureRectangle object with no storage allocated yet.
Parameters
ctx |
A CoglContext pointer |
|
width |
The texture width to allocate |
|
height |
The texture height to allocate |
Since: 1.10
Stability Level: Unstable
cogl_texture_rectangle_new_from_bitmap ()
CoglTextureRectangle *
cogl_texture_rectangle_new_from_bitmap
(CoglBitmap *bitmap
);
Allocates a new CoglTextureRectangle texture which will be
initialized with the pixel data from bitmap
. This texture is a
low-level texture that the GPU can sample from directly unlike
high-level textures such as CoglTexture2DSliced and
CoglAtlasTexture.
width
, height
) where width
and height
are the width and height of the texture.COGL_FEATURE_ID_TEXTURE_RECTANGLE
feature
using cogl_has_feature()
.The storage for the texture is not allocated before this function
returns. You can call cogl_texture_allocate()
to explicitly
allocate the underlying storage or preferably let Cogl
automatically allocate storage lazily when it may know more about
how the texture is going to be used and can optimize how it is
allocated.
Since: 2.0
Stability Level: Unstable
cogl_is_texture_rectangle ()
CoglBool
cogl_is_texture_rectangle (void *object
);
Gets whether the given object references an existing CoglTextureRectangle object.