Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] Bug Reporting => [Max] Resolved Bugs => Topic started by: johan belmans on 2015-10-02, 11:44:49

Title: Animation : parts of ballustrade in glass renders black
Post by: johan belmans on 2015-10-02, 11:44:49

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

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: Frood on 2015-10-02, 13:10:21

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

Good Luck

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: johan belmans on 2015-10-02, 13:21:09

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

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: maru on 2015-10-02, 14:12:05

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?

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: johan belmans on 2015-10-02, 15:46:22

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

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: johan belmans on 2015-10-02, 16:01:24

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

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: fellazb on 2015-10-02, 16:42:19

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

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: maru on 2015-10-02, 16:50:38

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.

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: johan belmans on 2015-10-02, 17:55:47

I will do Maru

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: romullus on 2015-10-04, 12:23:47

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.

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: Ondra on 2015-10-07, 16:13:45

maru: let me know what was the cause

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: maru on 2015-10-07, 16:32:27

@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

Title: Re: Animation : parts of ballustrade in glass renders black
Post by: johan belmans on 2015-10-07, 18:58:35

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.