Questions tagged [alpha]

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3answers
117 views

How do I add two color values containing alpha?

I started out writing my Color class as just containing R, G, B triplets. Adding colors in this situation turns out to be fairly simple. ...
0
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1answer
63 views

In alpha premultiplied sRGB a color component can't be greater than the alpha, right?

Afaik, in alpha premultiplied color the components stored so: [r * a, g * a, b * a, a] So the fully opaque white color is: ...
0
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1answer
70 views

OpenGL blending with the screen

I don't understand how OpenGL performs the blending of a texture on the screen. By default, the clear color is set to (0, 0, 0, 0). If we use the default blending equation GL_SRC_ALPHA and ...
1
vote
1answer
61 views

Given a background image B and a composie image of A OVER B, can we somehow recover image A?

I often find myself in the situation where I have some old image where I composed a translucent overlay on top of a background, but then lost (or more likely discarded) the overlay. I still have pre-...
3
votes
1answer
64 views

Repeating alpha over/under operation multiple times

I have two RGBA colors in linear [0..1] space, src and dst and I want to alpha blender src ...
1
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0answers
138 views

Sorting my geometry for alpha testing

Here is my predicament. I am trying to draw a multitude of dots that leave trails behind them real time. Heres the difficulty, that line fades. Each dot line has a defined z position and the goal ...
2
votes
2answers
2k views

How to perform additive blending in Metal. What do these terms mean?

Forgive me, I dont really understand the basis of alpha blending. Like I know the formula but when it comes to the terms blending operation, source blend factor, and destination blend factor I am ...
1
vote
1answer
52 views

Are w3.org docs correct?

I'm referring to this section: https://www.w3.org/TR/compositing-1/#simplealphacompositing Considering the formula co = Cs x αs + Cb x αb x (1 - αs) the docs state ...
4
votes
1answer
273 views

Avoid having an opaque and transparent variant of each pixel shader

Transparency can be achieved (or actually approximated) by using alpha-to-coverage (in case of MSAA) or basic alpha/transparency blending using the following approach: Bind a rasterizer state with a ...
0
votes
1answer
73 views

Make Object created in a list blend in/dissolve out of a scene

I have a number of (opaque) objects created using the glGenLists() glNewList() utilities. As generated, the Alpha values are all set to 1 Is there a way to make these objects when summoned blend into ...