topic Striped patchy baked occlusion in VRED Forum

Striped patchy baked occlusion

Neil_Cross — Wed, 03 Jul 2019 11:09:42 GMT

Hi guys - I've seen this on almost every CAD model (Inventor) I've imported into Vred, regardless of import type (STP, INV, DWF etc)

When I bake the occlusion onto the models, again regardless of quality settings, I get these jet black areas on flat faces which I'm finding impossible to smooth out.

Are there any optimisation techniques to work around this? These areas are all exposed to the environmental lighting and aren't obscured by other objects, they're all outward facing.

Re: Striped patchy baked occlusion

Christian_Garimberti — Wed, 03 Jul 2019 12:08:37 GMT

Hi Neil,

have you tried to activate the subdivision option in the bake light and shadow panel?

Same box imported from inventor, the left has baked with subdivision, the right without.

Chris

Re: Striped patchy baked occlusion

Christian_Garimberti — Wed, 03 Jul 2019 12:05:43 GMT

This could happens if you have shared geometries. if the first bolt to be baked is completely inside the model (so it have no light) the other bolts, if shared, receive the same shadow.

Chris

Re: Striped patchy baked occlusion

Neil_Cross — Wed, 03 Jul 2019 14:32:27 GMT

Yea I think they're unshared, I've just went to this node and done an Unshare, Unshare Node and Unshare Subtree on it, then baked the shadows using subdivision (they were before too, I used the car presets) and it still came out like this:

It definitely looks like a shadow from another object but I don't know how what from, I can isolate that part on its own so it isn't part of a group of objects.

Re: Striped patchy baked occlusion

Neil_Cross — Wed, 03 Jul 2019 15:27:31 GMT

So I just cleared the shadows from an object, ran it again with the below settings and got this unusual effect. This doesn't look like shadows from another shared object?

Re: Striped patchy baked occlusion

Christian_Garimberti — Wed, 03 Jul 2019 15:38:29 GMT

It doesn't seems to be a shared object.. but check the scenegraph

In the image you see the icons for shared nodes.

Could you share a part of your model to make some test?

... another maybe stupid question. Have you checked the normals?

Chris

Re: Striped patchy baked occlusion

Neil_Cross — Wed, 03 Jul 2019 20:58:54 GMT

The model is too big to attach, if I delete parts the shadows don't behave in the same way! I'll try and get something put together though.

But yea here's the nodes and normals...

Re: Striped patchy baked occlusion

michael_nikelsky — Thu, 04 Jul 2019 05:31:53 GMT

Hi,

the issue arises when your tessellation is too low. The calculation for the subdivision works by inspecting the results of the two vertices on an edge. If both have the same value, no subdivision is done. So in these cases I suspect that the vertices of the triangles are completely occluded and therefore the triangle will be black, even though there are regions of the triangle that should be lit.

You can try to enable the highest subdivision level to fix this. In this case the middle of the edge is also evaluated, so you increase the chance of detecting these scenarios.

If that also fails, the only solution is to increase the tessellation on these objects or just add some additional subdivisions.

Kind regards

Michael

Re: Striped patchy baked occlusion

Christian_Garimberti — Thu, 04 Jul 2019 06:23:19 GMT

I tied to reproduce what you say, Mychael, in a typical mechanical geometry from inventor.

The problem is that regardless of the tessellation level you use, you have always the same type of triangles.

The first plate is imported with Coarse, the second with High.

and this is from Dwf

With this type of geometry, very common in mechanical design, almost every triangle has a vertex on a hole. And the hole normally has a bolt inside... so explained the black plates...

Testing the subdivision level, as you told, i think that to keep the model simple but with good shadows, for me the best options is to keep tessellation low and do the subdivision with the highest quality only on the parts that have the problem.

1° row = low tessellation on import

2°row = high tessellation on import

2° column = no subdivision

3° column = subdivision low

4° column = subdivision high

What do you think?

Chris

Re: Striped patchy baked occlusion

Neil_Cross — Thu, 04 Jul 2019 09:24:51 GMT

The model I'm working with now is a DWF import (it was by far the best performance even after the optimisation dance) but there are no tesselation choices on import for DWF. However, if I subdivide a problematic part using a max edge length of around 5, then use medium subdivision on baking, it seems to resolve the patchy shadows for the parts I've gone over so far.

The problem with that being I've got around 40,000 parts in this scene! Not every one suffers from this issue but there's too many to do it part by part, but if I focus on the ones that are clearly in view it should be good enough!

Thanks again guys.