Animation : parts of ballustrade in glass renders black

[johan belmans]

Hi,

some part of my balustrade renders out black in some frames. Does any one has an idea to fix this? Or is this a bug?

Max 2016
DB: sept 6 2015
Ballustrade: instances of a box with chamfer modifier on
Material: glass thin (no refraction) enabled

Render settings: PT + UHD cache precomputed every 5th frame and reused for the whole sequence which is rendered on our farm with back burner.

If I render a frame locally with the same precaluculated UHD file, I sometimes do and sometimes don't have black parts in the ballustrade.

Not a valid vimeo URL

[Frood]

Looks like double faces to me. Can you check this?

Good Luck

[johan belmans]

No double faces, just a box with chamfer modifier on top.

[maru]

Can you check if this also happens if you disable UHD? (use pt+pt only)

Can you show the material, and the object up close?

[johan belmans]

Here you go. It seems that the glass is not thin. But still, mostly it renders well.
I will give PY + PT a try.

[johan belmans]

PT+PT will result in one hour extra rendertime per frame. Which is not an option.

[fellazb]

Perhaps it's the modifier? Try collapsing the geometry to an editable poly and see what happens.

[maru]

I just wanted you to check if this also happens when using PT+PT - this would mean that this is caused by UHD cache. You can for example region-render that part with the ballustrade for a few frames, or render it in lower res.

Also, please uncheck "legacy mode" in the glass material.

[johan belmans]

I will do Maru

[romullus]

Could be precission related. If scene units are set in meters and that glass plane is only few mm thick or if everything is quite far away from scene origin. Try to increase glass thickness and test render if it still happens.

[Ondra]

maru: let me know what was the cause

[maru]

@Ondra: I do not know yet. :)
@OP: did you manage to fix/overcome this? Can we have the scene, or the problematic part of it, at support? https://coronarenderer.freshdesk.com/support/tickets/new

[johan belmans]

Hi Guys

sorry I did not reply sooner. But we figured out what went wrong.
Circular xrefs, so the ballustrades where double in the file.

thanks for the suggestions.