scene translation time for heavy scene

[jasonhuang1115]

Hi,

I was glancing over this render engine review (https://cgworld.jp/feature/201704-cgw224T1-maya-2.html). Not gonna comment on the actual result as I saw render settings screenshot, but what got me interested is in the 2nd test where it's about heavy scenes that has many polygons and objects (all with default lambert shader and a dome light).
Based on the test results, the scene translation time is a big chunk of the overall render time for Vray (ranked last in comparison).


I had done similar test where Vray was taking a bit longer to kick off the rendering than other engines. Believe that improving scene translation time is under the radar of devs here. Just curious why is the scene translation time seems a bigger hurdle in comparison to other engines?

[vlado]

If you have scenes where you believe V-Ray is slower than it should be, please send them over so that we can profile them.

Best regards,
Vlado

[kosso_olli]

In comparison to 3dsMax the scene translation times often more than double in Maya on the same scene. But that might be Maya side of things, I suppose.

[vlado]

In comparison to 3dsMax the scene translation times often more than double in Maya on the same scene.

I'm not sure how that's relevant to anything. It can only tell you the speed differences between the Maya API and the 3ds Max API, nothing more... 3ds Max gives way more direct access to scene data.

Best regards,
Vlado

[Donfarese]

I think his main question is why the other renderers in that test seem to be doing scene translate much quicker than Vray.

[vlado]

I think his main question is why the other renderers in that test seem to be doing scene translate much quicker than Vray.

<shrug> If we knew that, we would have fixed it, don't you think One thing I know for example, is that Arnold doesn't deal with polygons with holes in them, whereas we try to triangulate them properly. This makes the Arnold export faster, but also broken in certain situations, however rare they may be. There are probably other things that we do and others don't. From our profiles though, most of that time is spent in Maya API functions, and not in V-Ray code. For sure it is possible that we are using the wrong (i.e. unoptimized) API calls, and we will have to look into it.

I could also argue that while the export time is larger, it is still reasonable and usually much lower than the total render time. Not that we shouldn't improve it, but in most cases it's not fatal in any way.

Best regards,
Vlado

[jasonhuang1115]

Thanks Vlado. The scene that I had tested was a production scene that I can't upload. As I test with other heavy scenes in the future that I can upload, I'd love to upload them for you to profile.

I am also curious with the Geometry/texture cache feature enabled, how much faster the scene translation time can be? Do you profile the difference as well internally?

[Donfarese]

Thank you Vlado, I'll be using VrayRT on an upcoming project and can give some insight on it's scene translate compared to say Redshift or Octane if that helps at all. I can provide the scene also. Really appreciate your help and info Vlado.

[kosso_olli]

3ds Max gives way more direct access to scene data.

Okay, nevermind then. As I said in the last post, most possibly it is Maya who is to blame for that. Nice to know that you can confirm it, so I can tell the Maya guys that 3dsMax is better

[snivlem]

Maya really sucks with scene translation with objects that have many face shading assignments. If you break up your objects on heavy scenes so that 1 shader is assigned to the object and not faces then it's much quicker. Or best yet, use vrmesh.

Not Chaos' fault, it's a core maya issue that will never be addressed as far as i'm concerned

[Bruce Allen]

I wish that the VFB's History had two timer values printed:
1. translation time
2. render time

This would help me diagnose which scenes to send to ChaosGroup.

Bruce Allen
Senior Theatrical Designer & TD - mOcean