now vulkan can do screenshots too. however, it depends on blits being
available between swapchain and rgba8 formats, so if it's not the case
for some reason, the resulting image will have mixed components.
after we've updated how brush index buffer references vertices to allow
for draw call coalescing ray tracing broke on amd.
this is because amd cards expect a correct value in
VkAccelerationStructureGeometryTrianglesDataKHR::maxVertex. make sure we
fill a correct value there.
make all geoms share the same constant vertex offset so that continuous indices can be exploited to generate only a single draw call for a group of geometries with the same texture
from: Mark Jarzynski and Marc Olano, Hash Functions for GPU Rendering, Journal of Computer Graphics Techniques (JCGT), vol. 9, no. 3, 21-38, 2020
http://www.jcgt.org/published/0009/03/02/
this is mostly copied from ray tracing gems 2 chapter 7 (Texture Coordinate Gradients Estimation for Ray Cones, by Wessam Bahnassi).
There's a weird bit about radians vs degrees. We'll figure it out later when the book becomes available.
this is very proof-of-concept quality. it should be definitely done some other way
e.g. we should control reflectivity and transparency differently (and not together)
and they should be based on texture ids, not on render_mode
it's also unfortunate that transparency required a lot of bounces. we should probably control transparency bounces separately from light bounces.
alternatively, transparency effects (beams, sprites) should be done with custom intersection shaders and not based on transparent geometry
We used to dispatch rays anyway even if there was no models to render and tlas wasn't built (which is the case for the first few frames).
This ended up crashing AMD gpu when using some (but not all) variants of rgen shaders.
With this change we'll check for whether there are any models to render, and if there are none, then we'll just clear frame to black.
This change also refactors ray tracing a bit.
for some reason amd will lose device whenever the first rendered frame has multiple push-constant-depndent bounces and break on line 138 in rgen.
when both break is commented out and bounces are compile-time constant, it will work just fine.
moreover, if we start xash with the workaround shader, get it to draw a few frames, and only then bring back both break and pc-bounces, recompile and reload shader, it will run just fine. not losing device and all.
wtf
- use non-uniform indexing because AMD requires it (which is technically correct by spec, it's just nvidia that supports it transparently)
- disable immutable samplers, as that breaks filtering on amd for some reason (TODO)
on amd gpus it won't draw anything at all unless you have the entire ray tracing pipeline set up fully and correctly:
- have at least rgen, rmiss and rchit shaders
- set up shader groups to reference them
- set up sbt to reference shader groups
it is not enough to just have a single rgen shader operating like a compute shader. amd will have a shader preamble that checks for something and exit early w/o actually running any shader code you wrote
meh
