I've awoken from my slumber

I've awoken from my slumber
Apr 22nd 2023, by Generic aka RSDuck

All the way back in early 2021 (I can't believe it's been 2 years) I wrote the compute shader renderer for the Switch port of melonDS as described in my previous post on it. If you don't know much about it the compute shader renderer then I recommend checking that post out.

After more or less completing it for Switch (the port desparately needs an update, it will come, I promise), I didn't really touch the code much. Over the last couple of weeks this finally changed.

The renderer had to be ported from Switch's homebrew GPU API deko3D to OpenGL, which fortunately wasn't that hard, because A. most of the complexity lies within the shader there is not that much buffer jougling and B. Nvidia GPUs (or atleast Maxwell) being somewhat of a OpenGL hardware implementation.

But let's come to the main attraction, besides some fixes, high resolution rendering is finally implemented for it. And it works wonderfully, with far fewer or no artefacts compared to the classic OpenGL renderer. And even on my integrated Intel UHD 620 I can reach up to 3x-4x resolution depending on the game.

With local wireless there is now another reason you might want to use it over the software renderer. If you are short on CPU cores for all the melonDS instances you can offload the rasterisation onto the GPU.

There are still a few things left to do. For some reason the shaders (which are all compiled on startup, so no stuttering while playing) seem to compile quite slowly on Windows for Intel and Nvidia GPUs. Bizzarely this seems to be related to the very large SSBOs, atleast reducing their size seems to lead to speed up. So my plan is to replace the large buffers which scale proportionally to the resolution with ones which have unspecified size or image load and store. If I had to guess the driver performs the layout calculation somehow for every array entry. In case I don't get the compile times low enough, I need to implement a shader binary cache.

The outlines generated through edge marking (e.g. used by the Zelda games) are always only pixel thick, which quickly becomes very thin for higher resolutions. Thus I want to add an option to counteract that (I am still not exactly sure how to do it.

Another issue that currently the compute shader renderer isn't integrated into the GUI at all, it currently just replaces the OpenGL renderer.

And like always there is still some clean up to be done in the code. As a last note, the compute shader renderer already uses a texture cache (which as part of this clean up should also be used by the OpenGL renderer). Implementing texture replacement on top of that is not hard and is on my list as well, but one step after the other.

And yes, it allows you to play Pokemon in higher resolutions with no back lines.

31 comments have been posted.

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Nin says:
Jul 8th 2024

Any update on texture replacement?

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