LayerBlendMode Enumeration
Represents the blend mode that will be used to blend the content of this layer into result of previous draws.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CECore assembly)
Syntax
public enum LayerBlendModeValues
| Value name | Value | Description |
|---|---|---|
| Normal | 0 | This mode will use the alpha component of the pixels to determine how much each pixel contributes to the final result. |
| Multiply | 1 | This mode will blend the red, green and blue components by using multiplication of the source and destination pixels. |
Remarks
The blend computation will be performed per pixel, where the source pixel is the pixel that is about to be drawn to the layer and the destination is the pixel that was already in the layer before the blend. The blend mode will modify two variables, s and d, in the blend equation: Fc = Sc * s + Dc * d, where Fc is the final color, Sc is the color component of the source pixel and Dc is the color component of the destination pixel. All variables in the blend equation have a range of [0, 1].
All implemented blend modes will compute the result alpha component for each pixel in the same way using the blend equation with s = source alpha, d = 1.0 for the alpha channel. This simplifies the blending equation to Dc + Sc * Sc, thus drawing an image with a non zero alpha component will always increase the opacity of covered pixels.
The opacity of the layer can be used to regulate how much the layer should contribute to the blend. A blend of a layer with opacity 0% will have no contribution, an opacity of 50% would have half the contribution, and an opacity of 100% will have full contribution.
Examples
Here follows a few examples of how the blend modes can be used and how they are computed.
Blend mode Normal
This mode will blend the red, green, and blue color components using the blend equation with s = source alpha and d = 1.0 - source alpha:
Fc = Sc * Sa + Dc * (1.0 - Sa)
If a pixel is drawn with an alpha value that is fully opaque, then only the source pixel will contribute to the result. If a pixel is drawn with 70% opacity then the resulting pixel is the sum of 70% of the source and 30% of the destination pixel.
Blend mode Multiply
This blend mode will perform component wise multiplication of the red, green, and blue components by using the blend equation with s = destination color and d = 0:
Fc = Sc * Dc + Dc * 0.0
Simplifying this and separating the components gives us the color:
(Fr, Fg, Fb) = (Sr * Dr, Sg * Dg, Sb * Db) where F is the final color, S is the source and D is the destination pixel. The subfixes r, g, and b is the red, green, and blue color components.
If a blue pixel with full opacity from a layer with blend mode multiply is blended into a white pixel with full opacity, then blue layer could be seen as a filter that only takes the blue channel from the destination pixel. The result pixel would have the resulting value:
(0.0, 0.0, 1.0) = (0.0 * 1.0, 0.0 * 1.0, 1.0 * 1.0)
A typical good use case for this blend mode is to blend the result from a ShadeOperator into a layer visualizing land use with unshaded colors. The opacity of the layer with the blend mode can be used to regulate how shaded we want the layer to look.
Restrictions
Blend modes does not work between layers under SurfaceOverlay and layers in GlobeView.SurfaceLayers.
Platforms
Windows, Linux, Android