Light Baking Crash

[cnd7jones]

Running through our first project with vray for unreal. when attempting to bake it goes for over an hour and then completely crashes and says out of memory. Attached is the end of log file (original was too large to attach).

[Alexander.Atanasov]

Hi cnd7jones,

If it says out of memory then either your GPU memory or your CPU RAM isn't enough to bake out the whole scene. What were your settings from the V-Ray Settings and V-Ray Bake Settings tabs? What is your hardware specs? A good workflow is to have the Export EXR option enabled when lightbaking because this way you can have a resumable baking in cases of crashes. You can check the docs here: V-Ray Bake.

Can you please send the content of PROJECT_NAME/Saved/Crashes and Logs folders at support@chaosgroup.com so we can take a look in the dump files from the crash.

Best regards,
Alexander

[cnd7jones]

I just ran through another scene and same issue. Forwarded the log file as requested. I'm glad there is sort of a work around, but it makes for overnight baking impossible. I'd have to set an alarm every hour over night to keep restarting the thing. My settings are pretty much what is preset out of box, preview quality. I've tried setting the atlas resolution to 1k and 2k with the same result.

[cnd7jones]

Alexander, is it possible to explain a little more about geometry their lightmaps and how the atlases work? I just noticed a message in the Message Log saying that there were 742 atlases to bake, i'm assuming this is the cause for the out of memory issue but what can i do on my end to resolve that? thanks!

[Alexander.Atanasov]

Hi cnd7jones,

Sorry for the late reply.

Alexander, is it possible to explain a little more about geometry their lightmaps and how the atlases work?

To have a proper bug-free bake each static mesh in the scene must have proper lightmap UVs (not going out 0-1 UV range and to not have overlapping UV islands). The quality of the bake depends on those UVs and on the Bake settings in the V-Ray Bake Settings tab. You can choose between 3 quality presets - Preview, Medium and High. You can check in the docs here for detailed information: V-Ray bake. In the Lightmap Atlas Resolution you set the maximum resolution to which static meshes will be packed for each atlas. When light baking with V-Ray we combine lightmaps of multiple nodes(static mesh actors) into atlases - a compoud image that contains the lightmaps of certain nodes. V-Ray for Unreal exports the visible actors into such atlases. Grouping objects in atlases improves light baking time. Higher resolution requires more video memory but enables faster light baking.
For example if you have 6 meshes with 512 light map resolution and you have set the Atlas resolution to 1024x1024, you will have 2 atlases - in the 1st there will be 4 meshes(2x512 in x and 2x512 in y) and in the 2nd 2 meshes(2*512 in x and 512 in y.) If you set the Atlas Resolution to 2048x1024 you will render out only 1 atlas (4*512 in x and 2*512 in y ). If there are meshes that have larger lightmap resolution than the set Atlas resolution, then that mesh will automatically resize the atlas.

I just noticed a message in the Message Log saying that there were 742 atlases to bake, i'm assuming this is the cause for the out of memory issue but what can i do on my end to resolve that? thanks!

Seems that you have a lot of meshes that you are trying to bake. I have seen the log that you have sent and saw that you are using a 2080 Ti and you have ray traycing enabled for the project. Keep in mind that when light baking with V-Ray it uses the devices that you have enabled in the VRay CUDA GPU Device Select category in the V-Ray Settings. With ray tracing enabled means that Unreal will use more resources which means that V-Ray will have less resources to work with during the baking process.
I would suggest to disable the ray tracing only for the baking part and enable it after it is done. Also if the memory of the GPU isn't enough (in your case 11Gb) then disable the GPU in VRay CUDA GPU Device Select and enable only the CPU. This way V-Ray will use only the CPU RAM which is more than the GPU.


We have shipped a new build (4.20.00 - Download) yesterday where we have some improvements and bugfixes. Try it with the suggestions above and tell me how it goes.
Best regards,
Alexander

[cnd7jones]

Alexander, THANK YOU! great responses and i love that fact that we now get a status indicating progress. I will give the CPU version a try and report back. I noticed in the latest version that we can no longer select the rendering device from within Unreal? If using CPU only is the only way to bake large scenes it would be much easier to switch in the application than having to use the external one. Thanks again!

[Alexander.Atanasov]

Hi cnd7jones,

Thank you for the feedback. The lack of VRay CUDA GPU Device Select from within the V-Ray Settings is a bug. We will try to fix this as soon as possible.

Best regards,
Alexander

[cnd7jones]

Just wanted to report back that you were correct. Switching to the CPU render solved the memory issue. Not really a great solution since we don't have anything here CPU wise that is worth baking an entire scene on but its something. Thanks again for all the help.