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by pjmlp
950 days ago
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The new modern APIs are not to be understood as graphics APIs, rather as GPU APIs, thus using them directly is more akin to writing a graphics device driver than a rendering engine. Most people are better served by using GL 4.6, DX 11 and such, or a middleware engine. Even console vendors have multiple APIs because of that, not everyone needs all little details of the GPU. Unity is supposed to have good DirectX 12 coming up, by the way. "Achieving Real Time Ray Tracing on Xbox with Unity and DirectX12" https://www.youtube.com/watch?v=giaEpbBGc6E |
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I've heard this repeated a lot in internet forums, but my experience working through hundreds of pages of Frank Luna's 800+ page DX12 book before concluding it pointless for 2D was that DX12 is actually fundamentally very similar to DX11 with most of the API focused on graphics rather than general compute. Compute shaders are just one chapter (13) of Luna's book, roughly 40 of the 800+ pages. I did some of the LunarG Vulkan tutorial and browsed the Khronos ref pages and reached a similar conclusion for Vulkan. I played with CUDA a bit and that's what real GPU programming looks like, almost no mention of graphics for much of the documentation. The "hello world" program isn't drawing a triangle, it's adding two arrays. Whereas a great deal of DX12, Vulkan, etc. is all about pixel formats, pixel shading, swap chains, geometry and tessellation, blending, depth and stencil, mipmaps and cube maps, clip coords, triangle winding and culling, the perspective Z divide, viewports, indexed and instanced draw calls, ... you know, graphics. But in chapter 9 of the DX12 book, end of 9.4, Luna writes, "Texture atlases can improve performance because it can lead to drawing more geometry with one draw call." So the conclusion I reached is that DX12 doesn't offer some fancy GPU compute way of writing a GPU program that can use 1000 distinct textures to draw 1000 distinct quads using only one CPU function call to launch this GPU program.
Now I've been doing more research and there is some sort of new feature called bindless textures not covered in Luna's DX12 book that might accomplish what I want (I'm not sure), but it seems to be Win11 only, WDDM 3.0 only, shader model 6.6 only, very new cards only. With this feature I might be able to set up 1000 distinct integer ids for my 1000 distinct textures, and then, with one single CPU draw call, have those 1000 textures applied to the correct 1000 quads, with no need to pack those 1000 textures into an atlas. Doing more web searching just now, this possibly can also be done in OpenGL on cards that support NV_gpu_shader5, but only semi-recent nVidia cards might support this. (I'm finding it difficult to get quick, quality answers to these sorts of questions using either web searches or LLMs.) Anyway, a gamedev forum or DX-focused reddit might be a better place for me to ask these sort of technical questions.