Effects

Orka provides a few packages which can be used for post-processing of textures.

Info

The various objects described on this page are declared in the package Orka.Rendering.Effects and its child packages.

Filters

The package Orka.Effects.Filters provides the following filters:

• Separable filter. Needs a Float_32_Array representing the kernel. A function which returns a Gaussian kernel is provided.
• Moving average filter

A Gaussian blur using the separable filter gives better performance than the moving average filter for small kernels (weak blurs). However, the moving average uses a computer shader with a O(1) time complexity and provides a consistent performance independent of the blur radius.

Separable filter

The type Separable_Filter can be used to apply a Gaussian blur to a texture. First create a kernel and then the separable filter by calling the function Create_Filter:

Kernel   : Float_32_Array   := Gaussian_Kernel (Radius => 24);
Filter_1 : Separable_Filter := Create_Filter (Location, Texture_1, Kernel);

The Kernel must consist of a sequence of offsets, followed by a sequence of weights. The function Gaussian_Kernel takes care of this. Good values for Radius for weak, normal, or strong blurs are 6, 24, and 48.

The filter can then be applied to the texture:

Filter_1.Render (Passes => 1);

For better performance, it is recommended to first downsample a texture to half the size (with procedure Resolve_To in the package Orka.Rendering.Framebuffers) before applying the filter to it. However, this can visibly reduce the quality of the image for very small kernels.

Moving average filter

The type Moving_Average_Filter provides a filter that computes the moving average per row in a compute shader for a O(1) time complexity. This gives it a consistent performance which does not depend on the blur radius. The filter does not require a kernel and can be created immediately by calling the function Create_Filter:

Filter_2 : Moving_Average_Filter := Create_Filter (Location, Texture_1, Radius => 4);

Good values for Radius for weak, normal, or strong blurs are 1, 4, and 8. After the filter has been created, it can be applied to the texture:

Filter_2.Render (Passes => 2);

With a single pass the moving average filter acts as a box blur. The filters should be applied multiple times so that it approximates a Gaussian blur. By default it is applied in two passes.