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Bug 3594 - Bitwise blending mode
Summary: Bitwise blending mode
Status: RESOLVED WONTFIX
Alias: None
Product: SDL
Classification: Unclassified
Component: render (show other bugs)
Version: HG 2.1
Hardware: All All
: P2 enhancement
Assignee: Sam Lantinga
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-03-01 08:44 UTC by Vitaly Novichkov
Modified: 2017-08-14 08:11 UTC (History)
0 users

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Description Vitaly Novichkov 2017-03-01 08:44:22 UTC 
I wasn't found the way to have bitwise "or" and bitwise "and" blending mode,
I.e. as

"buffer.rgb |= img.rgb" and "buffer.rgb &= img.rgb"

I want to use this mode for some graphical effects are impossible with alpha-blending, like the mountain has the invisible tunnel which can be shown when a special light filter will be drawn over the mountain.
Comment 1 Sam Lantinga 2017-08-11 17:47:37 UTC 
Feel free to submit a patch for the various rendering implementations, including the software renderer.
Comment 2 Sam Lantinga 2017-08-14 07:12:17 UTC 
As far as I can tell these blending modes are impossible without a custom pixel shader, which is outside the scope of the SDL renderer.
Comment 3 Vitaly Novichkov 2017-08-14 08:11:58 UTC 
My thinks:
- In case of software renderer that must be easy
- In case of OpenGL I guess, some extensions are needed (the example where are various render modes shown: https://github.com/WohlSoft/LunaLua/blob/ee86b73c1976051d3ad18f259e36724310de2124/LunaDll/Rendering/GL/GLDraw.cpp#L54-L90, it uses GLEW library which is used to manage extensions)
- In case of OpenGL ES would be similar as with desktop OpenGL.
- In case of Direct X - IDK, I never used DX by myself. Did you actually meant Direct X?