Rectangle textures (non-normalized coordinates)

Rectangle textures (non-normalized coordinates) — Functions for creating and manipulating rectangle textures for use with non-normalized coordinates.

Synopsis

                    CoglTextureRectangle;
CoglTextureRectangle * cogl_texture_rectangle_new_with_size
                                                        (CoglContext *ctx,
                                                         int width,
                                                         int height,
                                                         CoglPixelFormat internal_format);
CoglTextureRectangle * cogl_texture_rectangle_new_from_bitmap
                                                        (CoglBitmap *bitmap,
                                                         CoglPixelFormat internal_format,
                                                         CoglError **error);
CoglBool            cogl_is_texture_rectangle           (void *object);

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().

Details

CoglTextureRectangle

typedef struct _CoglTextureRectangle CoglTextureRectangle;

cogl_texture_rectangle_new_with_size ()

CoglTextureRectangle * cogl_texture_rectangle_new_with_size
                                                        (CoglContext *ctx,
                                                         int width,
                                                         int height,
                                                         CoglPixelFormat internal_format);

Creates a new CoglTextureRectangle texture with a given width, height and internal_format. This texture is a low-level texture that the GPU can sample from directly unlike high-level textures such as CoglTexture2DSliced and CoglAtlasTexture.

Note

Unlike for CoglTexture2D textures, coordinates for CoglTextureRectangle textures should not be normalized. So instead of using the coordinate (1, 1) to sample the bottom right corner of a rectangle texture you would use (width, height) where width and height are the width and height of the texture.

Note

If you want to sample from a rectangle texture from GLSL you should use the sampler2DRect sampler type.

Note

Applications wanting to use CoglTextureRectangle should first check for the 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.

ctx :

A CoglContext pointer

width :

The texture width to allocate

height :

The texture height to allocate

internal_format :

The desired internal texture format

Returns :

A pointer to a new CoglTextureRectangle object with no storage allocated yet.

Since 1.10

Stability Level: Unstable


cogl_texture_rectangle_new_from_bitmap ()

CoglTextureRectangle * cogl_texture_rectangle_new_from_bitmap
                                                        (CoglBitmap *bitmap,
                                                         CoglPixelFormat internal_format,
                                                         CoglError **error);

Allocates a new CoglTextureRectangle texture which will be initialized with the pixel data from bitmap. Internally the data will be stored in the format given by internal_format. This texture is a low-level texture that the GPU can sample from directly unlike high-level textures such as CoglTexture2DSliced and CoglAtlasTexture.

Note

Unlike for CoglTexture2D textures, coordinates for CoglTextureRectangle textures should not be normalized. So instead of using the coordinate (1, 1) to sample the bottom right corner of a rectangle texture you would use (width, height) where width and height are the width and height of the texture.

Note

If you want to sample from a rectangle texture from GLSL you should use the sampler2DRect sampler type.

Note

Applications wanting to use CoglTextureRectangle should first check for the COGL_FEATURE_ID_TEXTURE_RECTANGLE feature using cogl_has_feature().

bitmap :

A CoglBitmap

internal_format :

the CoglPixelFormat to use for the GPU storage of the texture

error :

A return location for a CoglError or NULL

Returns :

A pointer to a newly allocated CoglTextureRectangle texture or if the size was too large or there wasn't enough memory NULL is returned and error set.

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.

object :

A CoglObject

Returns :

TRUE if the object references a CoglTextureRectangle, FALSE otherwise.