OpenGL shading?

[JiffyRob]

This is an issue to debate the necessary-ness of implementing OpenGL GPU shaders in the game. This would allow for fast processing of effects to the screen and other surfaces. Some examples of what we could do would be:

• Dynamic shadows on all game objects
• GPU-accelerated day/night cycle
• GPU-accelerated camera scrolling
• Fancy particles and lighting system (yeah, dynamic shadows)
• GPU-accelerated limited-visibility in dark buildings, etc
• Interesting transition effects
• etc. Additionally, all of these would be rendered incredibly fast compared to doing it via vanilla pygame. Pretty much everything would be put in a separate package, probably bush.gl. This would have utilities for creating shaders and applying them to surfaces. Downsides:
• New dependency of the ModernGL library (I suppose we could use PyOpenGL, but ModernGL is a lot easier to use)
• OpenGL shading is a whole lot of work to implement
• In order to create all these effects we would have to learn GLSL, a language similar to C.
• Shaders don't debug nicely.
• The game might not work on (very) old hardware, depending on what versions we use
• There might be an issue of subtracting from the retro aesthetic of our game.

I'm kind of leaning toward yes, because bush was meant to be reusable, and not just specific to this game. If we decide not to use it now, we could still use it later.

At any rate, we should probably do this last, as most of the things listed above are either optimizations of current features or fancy eye-candy that leaves game play unchanged.

[JiffyRob]

This video is good if you want to know how to implement it: https://www.youtube.com/watch?v=LFbePt8i0DI

[JiffyRob]

As far as learning GLSL, the basics are not terrible. It is a wee bit impossible to debug though. I managed to make a colored lighting sphere with minimal pain.

[JiffyRob]

It also broke pygame.image.get_surface() which previously was used for screenshots. Instead you have to take the OpenGL context and send a buffer from it to a pygame surface. Then you can save that.

[JiffyRob]

Maybe this ought to be implemented sooner rather than later. This would replace a lot of code - particle effects(?), camera scrolling, weather cycle, camera shake, fancy map transitions, etc.

[JiffyRob]

Just found a downside: We very likely would not be able to make a web build if we used ModernGL. There is another library called ZenGL which allegedly works better on the web, but I don't know for sure.

[JiffyRob]

I've been working on particles and am not overly impressed with the performance I am getting. I house my benchmark program at this repo. Currently it is private, so you may not see it, but once it is successfully web built, it will be made public. I currently get about 4300 cows on desktop, and less on web. ZenGL looks to support the web platform, so I may try to get that to work.

[JiffyRob]

As of now zengl shading will not be added to the game due to the inherent constraints of the library. We'll see if pygbag can do another library or zengl improves down the line.