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ShaderImage

Provides Image access to shader programs. More...

Import Statement: import Qt3D.Render 2.4
Since: Qt 5.14
Instantiates: QShaderImage

Properties

Detailed Description

To make the content of textures available for read and write operations in a shader, they need to exposed as ShaderImage. Textures can be composed of several mip levels, layers and faces. Additionally declaring a ShaderImage allows specifying which level, layer or face of the texture content we want to access.

ShaderImage has to be assigned as a Parameter's value and reference a valid Qt3D.Render.AbstractTexture to work properly.

If the referenced texture is a one-dimensional array, two-dimensional array, three-dimensional, cube map, cube map array, or two-dimensional multisample array texture, it is possible to bind either the entire texture level or a single layer or face of the texture level. This can be controlled with the layered property.

Support for ShaderImage is only supported with OpenGL 4 and partially with OpenGL ES 3.1 and 3.2.

OpenGL 4 supports the following image types:

GLSL Type OpenGL Type Enum Texture Type
image1D GL_IMAGE_1D Texture1D
image2D GL_IMAGE_2D Texture2D
image3D GL_IMAGE_3D Texture3D
image2DRect GL_IMAGE_2D_RECT TextureRectangle
imageCube GL_IMAGE_CUBE TextureCubeMap
imageBuffer GL_IMAGE_BUFFER TextureBuffer
image1DArray GL_IMAGE_1D_ARRAY Texture1DArray
image2DArray GL_IMAGE_2D_ARRAY Texture2DArray
imageCubeArray GL_IMAGE_CUBE_MAP_ARRAY TextureCubeMapArray
image2DMS GL_IMAGE_2D_MULTISAMPLE Texture2DMultisample
image2DMSArray GL_IMAGE_2D_MULTISAMPLE_ARRAY Texture2DMultisampleArray
iimage1D GL_INT_IMAGE_1D Texture1D
iimage2D GL_INT_IMAGE_2D Texture2D
iimage3D GL_INT_IMAGE_3D Texture3D
iimage2DRect GL_INT_IMAGE_2D_RECT TextureRectangle
iimageCube GL_INT_IMAGE_CUBE TextureCubeMap
iimageBuffer GL_INT_IMAGE_BUFFER TextureBuffer
iimage1DArray GL_INT_IMAGE_1D_ARRAY Texture1DArray
iimage2DArray GL_INT_IMAGE_2D_ARRAY Texture2DArray
iimageCubeArray GL_INT_IMAGE_CUBE_MAP_ARRAY TextureCubeMapArray
iimage2DMS GL_INT_IMAGE_2D_MULTISAMPLE Texture2DMultisample
iimage2DMSArray GL_INT_IMAGE_2D_MULTISAMPLE_ARRAY Texture2DMultisampleArray
uimage1D GL_UNSIGNED_INT_IMAGE_1D Texture1D
uimage2D GL_UNSIGNED_INT_IMAGE_2D Texture2D
uimage3D GL_UNSIGNED_INT_IMAGE_3D Texture3D
uimage2DRect GL_UNSIGNED_INT_IMAGE_2D_RECT TextureRectangle
uimageCube GL_UNSIGNED_INT_IMAGE_CUBE TextureCubeMap
uimageBuffer GL_UNSIGNED_INT_IMAGE_BUFFER TextureBuffer
uimage1DArray GL_UNSIGNED_INT_IMAGE_1D_ARRAY Texture1DArray
uimage2DArray GL_UNSIGNED_INT_IMAGE_2D_ARRAY Texture2DArray
uimageCubeArray GL_UNSIGNED_INT_IMAGE_CUBE_MAP_ARRAY TextureCubeMapArray
uimage2DMS GL_UNSIGNED_INT_IMAGE_2D_MULTISAMPLE Texture2DMultisample
uimage2DMSArray GL_UNSIGNED_INT_IMAGE_2D_MULTISAMPLE_ARRAY Texture2DMultisampleArray

OpenGL ES 3.1 supports the following image types:

GLSL Type OpenGL Type Enum Texture Type
image2D GL_IMAGE_2D Texture2D
image3D GL_IMAGE_3D Texture3D
imageCube GL_IMAGE_CUBE TextureCubeMap
image2DArray GL_IMAGE_2D_ARRAY Texture2DArray
iimage2D GL_INT_IMAGE_2D Texture2D
iimage3D GL_INT_IMAGE_3D Texture3D
iimageCube GL_INT_IMAGE_CUBE TextureCubeMap
iimage2DArray GL_INT_IMAGE_2D_ARRAY Texture2DArray
uimage2D GL_UNSIGNED_INT_IMAGE_2D Texture2D
uimage3D GL_UNSIGNED_INT_IMAGE_3D Texture3D
uimageCube GL_UNSIGNED_INT_IMAGE_CUBE TextureCubeMap
uimage2DArray GL_UNSIGNED_INT_IMAGE_2D_ARRAY Texture2DArray

OpenGL ES 3.2 supports all of the OpenGL ES 3.1 image types as well as the following:

GLSL Type OpenGL Type Enum Texture Type
imageBuffer GL_IMAGE_BUFFER TextureBuffer
imageCubeArray GL_IMAGE_CUBE_MAP_ARRAY TextureCubeMapArray
iimageBuffer GL_IMAGE_BUFFER TextureBuffer
iimageCubeArray GL_INT_IMAGE_CUBE_MAP_ARRAY TextureCubeMapArray
uimageBuffer GL_UNSIGNED_INT_IMAGE_BUFFER TextureBuffer
uimageCubeArray GL_UNSIGNED_INT_IMAGE_CUBE_MAP_ARRAY TextureCubeMapArray

Expected use would look like:

import Qt3D.Render 2.14

Entity {
...
    Texture2D {
        id: tex2D
        ...
    }

    Material {
        parameters: Parameter {
            name: "imageUniformName"
            value: ShaderImage {
                texture: tex2D
            }
        }
        ...
    }
 ...
}

Property Documentation

access : enumeration

Specifies the type of access we want to allow from our shader instances to the image. If a shader tries to write or read from an image that has incompatible access, the behavior is undefined.

Constant Description
ShaderImage.ReadOnly Read-only access.
ShaderImage.WriteOnly Write-only access.
ShaderImage.ReadWrite Read-write access.

The default value is ShaderImage.ReadWrite.


format : enumeration

Specifies the image format, which is essentially important when storing values in the ShaderImage from a shader.

The format doesn't have to be the same as the referenced texture's format. It however has to be compatible (matching in size but not necessarily by class type). For instance a texture of format R32F (size 32bits, class 1x32) could be used with an image of format RGBA8I (size 32bits, class 4x8). Table 8.27 of the OpenGL specifications shows the size and class for all supported image formats.

By default Qt3D will try to set the image format to match that of the referenced texture.

The default value is ShaderImage.Automatic.


layer : int

Holds which layer out of the referenced texture should be used for the ShaderImage. This property does nothing if layered is set to true or if the reference texture's type isn't compatible with layers.

Note: When the referenced texture is of type cube map or cube map array and ─║ayered is set to false, the face and layer are retrieved in the following manner:

cubeMapLayer = layer / 6
cubeMapFace = layer - (cubeMapLayer * 6)

The default value is 0.


layered : bool

*

If set to true, if the referenced texture is a one-dimensional array, two-dimensional array, three-dimensional, cube map, cube map array, or two-dimensional multisample array texture, the entire level will be bound for all layers. If set to false, only the single layer specified by the layer property will be bound.

The default value is false.


mipLevel : int

Holds which mipLevel out of the referenced texture should be used for the ShaderImage.

The default value is 0.


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