Sadly we had to disable point cloud rendering in HIP-RT (what is probably used for particle rendering in the scene you’re testing) as it brought a 3x performance regression to ALL scenes, making it significantly slower than normal HIP.
We are aware of this issue and apparently AMD is working on making some adjustments to HIP-RT, and potentially Cycles to fix this issue in a future release of Cycles.
We are also aware of a bunch of other issues with HIP-RT. And this is why it is disabled by default and is labeled as an experimental feature.
Unfortunately. Despite great progress and surprisingly fast rendering in many situations, for rx 6600 xt, HIP is still an experimental feature. Many demo projects from the official website don’t run on Linux. E.g. the one with the glacier and boat, the one with dinosaurs and one with interior visualization. I’m talking about the ones I’ve tested. The program, after trying to preview, just shuts down. Barbershop takes a very long time to load. I thank the developers for improving the situation, but I think Hip should still be officially recognized as an experimental feature and not tested thoroughly enough. I’m still keeping my fingers crossed for AMD.
I’m not aware of most of those issues with HIP on Linux. I’ll double check here with my GPUs.
I think I know what that one is about. HIP uses the BVH2 BVH, and it can take a long time to construct the BVH2 BVH in “viewport mode” in that scene due to the number of objects and scene settings.
With at least RDNA1 (and possibiliy RDNA2 based on your report), scenes containing Manifold Next Event Estimation can freeze when trying to render them.
I would still recommend you do a bit of your own investigation to see if it is actually the same issue.
The one with dinosaurs (I assume you mean Art Gallery — Blender Cloud). That scene has a lot of hair in it, and the BVH2 BVH used by HIP isn’t that memory effcient with hair. This results in that scene typically seeing a a 50+GB peak of memory usage during scene intialization. During rendering it uses ~17GB of memory, which exceeds the VRAM of your GPU, and may not work properly with the host memory fallback feature.
This isn’t a issue limited to HIP, it’s a issue with all backends that use the BVH2 BVH:
CUDA
Standard oneAPI
Standard Metal
And CPU (with some debug settings)
This has typically been “fixed” by using more effcient curve representations in the BVH provided by the GPU manufacturer (E.g. OptiX, MetalRT, and Embree). But sadly HIP-RT doesn’t (currently) offer a memory effcient curve representation, and I believe there may actually be a issue in Cycles that leads to “super memory ineffcient curve representations” when using HIP-RT.
The Interior visualization scene (I assume you mean Blender 4.1 – Lynxsdesign from here). I’m not 100% sure about this one.
It consumes a bit of memory due to the hair on the rug, but I’m not sure if it’s enough to cause issues for your system with the amount of RAM and VRAM you have.
Or mabe there’s some other issue with this scene, I don’t know.
Just so things are clear for users about the current state of HIP and HIP-RT.
Both HIP and HIP-RT are known to have issues. HIP-RT more so than HIP, older GPUs more so than newer GPUs, and Linux more so than Windows.
Just to give some perspecitve on that, the Cycles module has a “standard” test suite. It tests many different areas of Cycles.
Thre is a more “complete” test suite, but it’s rarely run as it’s impartical to align the test results across many different devices.
At this current point in time:
My AMD RX 7800XT passes the standard test suite with HIP on both Windows and Linux.
My AMD RX 5700XT does not pass the standard test suite with HIP on either Windows or Linux, with Linux having 1 or 2 more failures. Luckily the issues are limited to a small area of Cycles, shader ray tracing (Bevel and shadow caustics).
Neither my RX 7800XT or RX 5700XT pass the standard test suite with HIP-RT on Windows or Linux with many test failures.
Along with that, different hardware also appear to have their own set of issues. Here’s a list of the issues I know about so far:
Instinct GPUs are not supported.
Older Instinct GPUs have major rendering artifacts.
Newer Instinct GPUs do not appear to have native texture handling and so the kernels fail to compile. This could be worked around, but was deemed not worth doing at this current point in time.
Depending on your HIP-Runtime version on Linux, rendering with 3D textures (like a OpenVDB file) can cause Blender to crash.
This has been fixed in Blender 4.4, there are plans to backport this to 4.2 LTS.
On some devices, volumetric materials can render with artifacts with HIP on Linux. RX 7600 and RX 6800 have been confirmed to have this issue. Yet the RX 7800XT and RX 5700XT do not, so this issue is highly device dependent.
Upgrading the HIP compiler seems to fix this, so there is a plan to upgrade for Blender 4.4.
Shader ray tracing (Bevel shader and Shadow Caustics) on HIP on older GPUs (E.g. RX 5700XT) can have rendering artifacts, or lock up Blender or the GPU driver
There are plans to refactor the shadow caustics system, which as a side effect may fix the shadow caustics issue.
Alternatively updating the HIP compiler or making adjustments to the code may fix the issue.
HIP-RT fails to render many scenes properly
Point clouds do not render.
As mentionied in a previous comment, this was done to avoid a performance regression
Curve motion is incorrect for motion blur and motion vector passes.
Transparent shadows can render improperly.
Meshes with subsurface scattering and with motion blur enabled, can render black.
Some scenes will fail to start rendering if specific (rarely used) settings are enabled.
There are precision issues with:
Large objects
Probably small objects
Objects with certain transformations
Rays that travel long distances (common in Orthographic view)
HIP-RT is less memory effcient than HIP with curves (And HIP already wasn’t that effcient)
And related to HIP, HIP OIDN only supports a small number of AMD GPUs.
For the HIP-RT issues, some of them are on the Cycles integration side, some of them are on the HIP-RT library side. I do not know for certain where each issue falls.
Almost all of the issues above are being tracked on the Blender bug tracker (and some may be on AMD’s internal bug tracker).
Just to quickly add a note. I am a triager, I see a lot of bug reports, and I personally have a wide range of devices I can use for testing. No GPU backend is perfect. CUDA, OptiX, HIP, HIP-RT, oneAPI, Metal all have their own set of issues. It’s just that HIP and HIP-RT are significantly more likely to have issues than the other GPU backends when testing with recently released GPUs.
You said “My AMD RX 7800XT passes the standard test suite”, and then said
“Neither my RX 7800XT or RX 5700XT pass the standard test suite.”. So I think you meant neither passed the complete test suite.
The RX 7800XT passes the standard test suite with HIP, but doesn’t pass the standard test suite with HIP-RT. This clarification is already in the original comment.
