Using cycles-x latest headless on Linux, I notice that in 4cf3efaa43b of July 13 Brecht removed cycles.preferences.get_devices() which I had been using to initialize & enable the CUDA devices in my headless renders, in my render startup script. If I don’t call that, my renders don’t seem to get CUDA-accelerated (I don’t know of a debug flag to definitively prove that but the renders are slow).
I’m guessing that wasn’t ever part of the public API, and I should be doing something else to enable CUDA/OPTIX.
I’ll note that if I do this instead of calling get_devices I get my CUDA speedups back:
import _cycles
for device_type in ('CUDA', 'OPTIX'):
self.update_device_entries(_cycles.available_devices(device_type))
I encuntered an interesting issue when trying to use Photographer addon’s physical light workflow in Cycles X, something seems to be wrong with the light threshold.
For those don’t know, Photographer addon provides physical light units like Lumen and Candela, but because the actual brightness of lights can differ drastically (sun at noon when using Nishita at 90 degrees sun height, vs a 800 lumen light bulb that is around 1 to 2 blender w), it usually needs to be used along with Photographer addon’s physical camera exposure. When having dim light and adjusted exposure to brighten the scene, the light would become extremely noisy because Cycles would lower the samples of dimmer value light. Solution in the master is to adjust the light threshold according to the exposure or you can also just turn it to 0:
I tried to to the same thing in Cycles X and something about the light threshold is not right. I recorded a video here, I did not use the addon tool and I adjust everything with Blender built-in buttoms:
What is going on? I want to ask whether this is a bug or a “feature”, if it is not a bug, I am afraid the physical light workflow in Blender would suffer a huge impact. If it’s just a bug then I am more relieved that it would probably get fixed later on.
the AO pass is kinda messed up, latest cycles x build on the right (blender-3.0.0-alpha+cycles-x.e596936336d9-windows.amd64-release)
i usually use eevee to set the material blend mode and shadow mode to alpha hashed in all materials with transparency, but cycles don’t care about it, even eevee cares about it, anything that i do makes cycles x care about AO in my transparent materials
The most likely cause for the AO pass being “messed up” is due to the fact that the AO pass isn’t fully implemented yet. It has been added back to Cycles-X recently by making use of shader ray tracing, as talked about here: rB9aa5aeee46ae however shader ray tracing AO probably doesn’t take into consideration transparency properly and as such that might be why you’re facing this issue. It will hopefully be fixed when the AO pass is updated to use a technique other than shader ray tracing, something that seems to be planed based on the list here: ⚓ T87836 Cycles X - GPU Performance
is there any way of bypassing it? if I’m desperate enough i could use eevee just to render an AO pass separately and blend it into my composition, or use a older version of blender just for the AO pass
In the case of your scene it seems like transparency is used to cut out pixels from something resembling a Minecraft character. What you can do to get AO working “properly” is to cut out those pixels yourself by removing geometry rather than using a transparency texture.
If you don’t want to go through the process of cutting everything out, I would personally recommend rendering the AO again in a different render engine, regular Cycles or EEVEE, or render the entire scene in regular Cycles rather than parts in Cycles and parts in Cycles-X. As a side note, AO doesn’t need a lot of samples to resolve to a relatively noise free result, so if you’re rendering the AO pass in regular Cycles you can probably get away with a much lower sample count and still get comparable image quality.
So I was wondering if with all the recent progress on the Cycles-X project that is visible on the phabricator we can have some info about AMD and Intel GPU support?
I noticed a point about AMD in 2021-06-08 Blender Rendering Meeting
Can we possibly have a little snek peek what’s going on inside?
hmm not in my case, The denoise in the compositor uses open image which is completely fine on my side even with normal. Are you having problems with both optix and opening image?
Optix Viewport:
Open image is completely fine in both compositor and render tab both viewport and final, while optix has problem in the viewport and also in final render (EDIT: I messed up the setting in the previous edit and now the screenshots are fixed)
PS Also Cycles X is finally consistently faster then master on my machine now
also I thought the OIDN in render tab and compositor were the same, but apparently the compositor one is better.
I think it’s specifically the Optix denoising step that is much slower when both cards are enabled. When disabling Optix, using duel cards is substantially faster in the viewport. However, when enabling optix in the viewport, things get very very chuggy. There seems to be something broken about optix when more than one GPU is being used.
Cycles X is saying “Out of Memory” when rendering scenes @ 10,000x5,000 pixels, while non Cycles X would normally have handled this exact render. Is this a new limitation & need to upgrade 32gb ram or a bug maybe?
Hi, tiled rendering use less memory, they are working on tiles for high resolution images. This will be slower but you can render. Luxcore use this for Years now.
@mib2berlin While I like Luxcore overall, tiled rendering technically is available but I would not call it usable. It did a lot of tests, cause I often render high res scenes and it was not satisfactory. For one it’s almost impossible to set up and find the best settings unless you are willing to do a lot of test renderings for each scene. And then it comes with a compromise in quality if you really want to keep speed and memory in reasonable regions. The developers themselves admitted, this this is a relic that needs a lot of work to get up to date.
Just in case for those with GTX 9xx series and GPU not available and grayed out on render tab (at least on Linux). A workaround is, open the scene and then in Edit > Preferences > System tab, you do some modification there, for example choosing Optix tab and then CUDA tab again. In this way there is some kind of refresh and GPU will be available in render tab.
