class QSGTexture¶

The QSGTexture class is the base class for textures used in the scene graph. More…

Inherited by: QSGDynamicTexture

Synopsis¶

Methods¶

def __init__()
def anisotropyLevel()
def convertToNormalizedSourceRect()
def filtering()
def horizontalWrapMode()
def mipmapFiltering()
def resolveInterface()
def setAnisotropyLevel()
def setFiltering()
def setHorizontalWrapMode()
def setMipmapFiltering()
def setVerticalWrapMode()
def verticalWrapMode()

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description¶

Users can freely implement their own texture classes to support arbitrary input textures, such as YUV video frames or 8 bit alpha masks. The scene graph provides a default implementation for RGBA textures.The default implementation is not instantiated directly, rather they are constructed via factory functions, such as createTextureFromImage() .

With the default implementation, each QSGTexture is backed by a QRhiTexture, which in turn contains a native texture object, such as an OpenGL texture or a Vulkan image.

The size in pixels is given by textureSize() . hasAlphaChannel() reports if the texture contains opacity values and hasMipmaps() reports if the texture contains mipmap levels.

Materials that work with textures reimplement updateSampledImage() to provide logic that decides which QSGTexture ‘s underlying native texture should be exposed at a given shader resource binding point.

QSGTexture does not separate image (texture) and sampler objects. The parameters for filtering and wrapping can be specified with setMipmapFiltering() , setFiltering() , setHorizontalWrapMode() and setVerticalWrapMode() . The scene graph and Qt’s graphics abstraction takes care of creating separate sampler objects, when applicable.

Texture Atlases¶

Some scene graph backends use texture atlasses, grouping multiple small textures into one large texture. If this is the case, the function isAtlasTexture() will return true. Atlases are used to aid the rendering algorithm to do better sorting which increases performance. Atlases are also essential for batching (merging together geometry to reduce the number of draw calls), because two instances of the same material using two different QSGTextures are not batchable, whereas if both QSGTextures refer to the same atlas, batching can happen, assuming the materials are otherwise compatible.

The location of the texture inside the atlas is given with the normalizedTextureSubRect() function.

If the texture is used in such a way that atlas is not preferable, the function removedFromAtlas() can be used to extract a non-atlased copy.

Note

All classes with QSG prefix should be used solely on the scene graph’s rendering thread. See Scene Graph and Rendering for more information.

class WrapMode¶

Specifies how the sampler should treat texture coordinates.

Constant

Description

QSGTexture.Repeat

Only the fractional part of the texture coordinate is used, causing values above 1 and below 0 to repeat.

QSGTexture.ClampToEdge

Values above 1 are clamped to 1 and values below 0 are clamped to 0.

QSGTexture.MirroredRepeat

When the texture coordinate is even, only the fractional part is used. When odd, the texture coordinate is set to 1 - fractional part. This value has been introduced in Qt 5.10.

Constant	Description
QSGTexture.Repeat	Only the fractional part of the texture coordinate is used, causing values above 1 and below 0 to repeat.
QSGTexture.ClampToEdge	Values above 1 are clamped to 1 and values below 0 are clamped to 0.
QSGTexture.MirroredRepeat	When the texture coordinate is even, only the fractional part is used. When odd, the texture coordinate is set to `1 - fractional part`. This value has been introduced in Qt 5.10.

class Filtering¶

Specifies how sampling of texels should filter when texture coordinates are not pixel aligned.

Constant

Description

QSGTexture.None

No filtering should occur. This value is only used together with setMipmapFiltering() .

QSGTexture.Nearest

Sampling returns the nearest texel.

QSGTexture.Linear

Sampling returns a linear interpolation of the neighboring texels.

Constant	Description
QSGTexture.None	No filtering should occur. This value is only used together with `setMipmapFiltering()` .
QSGTexture.Nearest	Sampling returns the nearest texel.
QSGTexture.Linear	Sampling returns a linear interpolation of the neighboring texels.

class AnisotropyLevel¶

Specifies the anisotropic filtering level to be used when the texture is not screen aligned.

Constant

Description

QSGTexture.AnisotropyNone

No anisotropic filtering.

QSGTexture.Anisotropy2x

2x anisotropic filtering.

QSGTexture.Anisotropy4x

4x anisotropic filtering.

QSGTexture.Anisotropy8x

8x anisotropic filtering.

QSGTexture.Anisotropy16x

16x anisotropic filtering.

Constant	Description
QSGTexture.AnisotropyNone	No anisotropic filtering.
QSGTexture.Anisotropy2x	2x anisotropic filtering.
QSGTexture.Anisotropy4x	4x anisotropic filtering.
QSGTexture.Anisotropy8x	8x anisotropic filtering.
QSGTexture.Anisotropy16x	16x anisotropic filtering.

__init__()¶

Constructs the QSGTexture base class.

anisotropyLevel()¶

Return type:: AnisotropyLevel

Returns the anisotropy level in use for filtering this texture.

See also

setAnisotropyLevel()

commitTextureOperations(rhi, resourceUpdates)¶

Parameters:

rhi – QRhi
resourceUpdates – QRhiResourceUpdateBatch

Call this function to enqueue image upload operations to resourceUpdates, in case there are any pending ones. When there is no new data (for example, because there was no setImage() since the last call to this function), the function does nothing.

Materials involving rhi textures are expected to call this function from their updateSampledImage() implementation, typically without any conditions, passing state.rhi() and state.resourceUpdateBatch() from the RenderState .

Warning

This function can only be called from the rendering thread.

abstract comparisonKey()¶

Return type:: int

Returns a key suitable for comparing textures. Typically used in compare() implementations.

Just comparing QSGTexture pointers is not always sufficient because two QSGTexture instances that refer to the same native texture object underneath should also be considered equal. Hence the need for this function.

Implementations of this function are not expected to, and should not create any graphics resources (native texture objects) in case there are none yet.

A QSGTexture that does not have a native texture object underneath is typically not equal to any other QSGTexture , so the return value has to be crafted accordingly. There are exceptions to this, in particular when atlasing is used (where multiple textures share the same atlas texture under the hood), that is then up to the subclass implementations to deal with as appropriate.

Warning

This function can only be called from the rendering thread.

convertToNormalizedSourceRect(rect)¶

Parameters:: rect – QRectF
Return type:: QRectF

Returns rect converted to normalized coordinates.

See also

normalizedTextureSubRect()

filtering()¶

Return type:: Filtering

Returns the sampling mode to be used for this texture.

See also

setFiltering()

abstract hasAlphaChannel()¶

Return type:: bool

Returns true if the texture data contains an alpha channel.

abstract hasMipmaps()¶

Return type:: bool

Returns true if the texture data contains mipmap levels.

horizontalWrapMode()¶

Return type:: WrapMode

Returns the horizontal wrap mode to be used for this texture.

See also

setHorizontalWrapMode()

isAtlasTexture()¶

Return type:: bool

Returns whether this texture is part of an atlas or not.

The default implementation returns false.

mipmapFiltering()¶

Return type:: Filtering

Returns whether mipmapping should be used when sampling from this texture.

See also

setMipmapFiltering()

normalizedTextureSubRect()¶

Return type:: QRectF

Returns the rectangle inside textureSize() that this texture represents in normalized coordinates.

The default implementation returns a rect at position (0, 0) with width and height of 1.

removedFromAtlas([resourceUpdates=None])¶

Parameters:: resourceUpdates – QRhiResourceUpdateBatch
Return type:: QSGTexture

This function returns a copy of the current texture which is removed from its atlas.

The current texture remains unchanged, so texture coordinates do not need to be updated.

Removing a texture from an atlas is primarily useful when passing it to a shader that operates on the texture coordinates 0-1 instead of the texture subrect inside the atlas.

If the texture is not part of a texture atlas, this function returns 0.

Implementations of this function are recommended to return the same instance for multiple calls to limit memory usage.

resourceUpdates is an optional resource update batch, on which texture operations, if any, are enqueued. Materials can retrieve an instance from RenderState . When null, the removedFromAtlas() implementation creates its own batch and submit it right away. However, when a valid instance is specified, this function will not submit the update batch.

Warning

This function can only be called from the rendering thread.

resolveInterface(name, revision)¶

Parameters:

name – str
revision – int

Return type:

void

rhiTexture()¶

Return type:: QRhiTexture

Returns the QRhiTexture for this QSGTexture or null if there is none (either because a valid texture has not been created internally yet, or because the concept is not applicable to the scenegraph backend in use).

This function is not expected to create a new QRhiTexture in case there is none. It should return null in that case. The expectation towards the renderer is that a null texture leads to using a transparent, dummy texture instead.

Warning

This function can only be called from the rendering thread.

setAnisotropyLevel(level)¶

Parameters:: level – AnisotropyLevel

Sets the level of anisotropic filtering to level. The default value is AnisotropyNone , which means no anisotropic filtering is enabled.

Note

The request may be ignored depending on the graphics API in use. There is no guarantee anisotropic filtering is supported at run time.