External .vrscene files

[ebbmeister]

Hello

I'm currently evaluating the 3.5 demo for Modo. The integration is very solid - congrats!

I've been testing importing assets from 3dsmax via .vrscene files. When importing into the scene they render as expected in terms of speed. Also, when exporting them to proxies and referencing the external .vrmesh they load and render as expected in terms of speed also.

However, when referencing the external .vrscene files they render much slower. This is consistent for Production, RT CPU and RT GPU.

Is this a known issue or limitation?

Cheers
Phil

[vladimir.nedev]

I don't think referencing the .vrscene should lead to any slow down in terms of render speed.
Can you send me the scene or attach it here ?
What's the difference in render times ?

Greetings,
Vladimir Nedev

[ebbmeister]

Thanks for the quick response, Vladimir.

Email with scene file sent.

Cheers
Phil

[ebbmeister]

Hi Vladimir

Did you receive my scene file ok?

If so were you able to recreate the issue?

Cheers
Phil

[vladimir.nedev]

No, I don't have any e-mail concerning this issue.

Greetings,
Vladimir Nedev

[ebbmeister]

That's unusual... please check your spam folder in case. I've just re-sent it to your email using another address in case that helps.

Thanks
Phil

[vladimir.nedev]

Sorry, it was indeed in the spam folder (both e-mails). I haven't had to check in there for quite some time.
Thanks for the scene.

Greetings,
Vladimir Nedev

[ebbmeister]

Great. Thanks for letting me know

Cheers
Phil

[vladimir.nedev]

I did some tests on your scene and the .vrscene reference version is indeed somewhat slower than the .vrmesh version.
I measured between 6-15% slower.

It turns out that the .vrscene referencing will turn the scene into "dynamic" geometry to make it possible to instance it.
Note that the .vrmesh is also dynamic geometry.
In this particular case, the .vrmesh is probably slightly faster because the meshes get further sub-divided into voxels when exporting them to a .vrmesh.

The version with MODO meshes is the fastest one to render, because internally V-Ray uses static geometry for it.
The .vrmesh version seems to be around 32% slower than normal meshes.
I think usually this difference is smaller, but in your case, the car is split into many separate meshes, whose axis aligned bounding boxes intersect a lot.

If you want to improve the performance of .vrscene / .vrmesh for this scene, you can merge the meshes before exporting them to .vrmesh / .vrscene.
To do this:
1. select all meshes for the car
2. right click on any mesh -> change type -> mesh to make them editable
3. right click on any mesh -> merge meshes
4. delete the "Normal" normal map that MODO creates for the new mesh, or your normals will be messed up
5. now export a .vrmesh using the Convert to V-Ray Proxy command, or export a .vrscene using the "File -> Export As..." command
These new versions should be faster.

After doing this .vrmesh is around 23% slower than static meshes and the .vrscene is around 11% slower than static meshes.
So the .vrscene actually is faster than the .vrmesh when the meshes are merged first.

Note that I did all tests without any complex materials, just a simple diffuse one.
The difference will be much smaller if the scene had proper materials.

Greetings,
Vladimir Nedev

[ebbmeister]

Hi Vladimir

Thanks for your detailed explanation and finding from the scene.

My tests based on your information confirm that re-exporting the .vrscene as a single mesh increases performance significantly. When made up of many meshes, rendering the .vrscene can reach 30-40% before an image of the car even appears in progressive mode. As a .vrscene made from a single mesh, the car first appears in the render around 2%. That pretty much matches the performance of the proxy version and is much closer to normal Modo meshes.

Thanks for clearing that up - good to know how it works.

Cheers
Phil