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GI flicker wont go away.. tried everything

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Daniel De Silva
GI flicker wont go away.. tried everything
on Mar 20, 2018 at 2:17:45 am

Hi everyone,

So in my scene, there are small clustered, white dancing flickering artifacts from certain angles on my model as it rotates.

I'm aware this is a GI issue, but i've tried everything to no avail. Different large, small and medium irradiance caches, small medium large sampling, turning up the raytraced hard shadow samples.

But nothing seems to beat it.

Any ideas clever people of Creative Cow?

Thanks!

Dan.


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Steve Bentley
Re: GI flicker wont go away.. tried everything
on Mar 20, 2018 at 7:07:07 am

These might be perfectly flat poly's (I know, I know, all poly's are perfectly flat) but I mean to the camera's eye. A perfectly flat poly will only reflect a single pixel of a reflection map adn sometimes the same goes for a shadow map. So as the angle of incident changes as the camera moves, it's like you are dragging that reflection map across an opening that is only 1 pixel wide and that one colored pixel is getting plastered over the entire poly no matter how big it is. That pixel will change drastically as it moves.
Try adding either a subtle bump map of noise to the texture (standard noise scaled to 1000 and set to 2 in the bump strength) or try increasing your angle value in your phong tag on the object to "round" things out.



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Daniel De Silva
Re: GI flicker wont go away.. tried everything
on Mar 20, 2018 at 7:56:50 am

Hi Steve,

Thanks for the swift response. Tweaking those options don't seem to change anything unfortunately.

My only other educated guess is that it's due to the immense mess the mesh is in as it was imported from CAD? See below for the wireframe.



Thanks again,

Dan.


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Steve Bentley
Re: GI flicker wont go away.. tried everything
on Mar 20, 2018 at 8:07:51 am

It might be how the various textures assigned to the different sets of polys are being mapped. Did you texture it? or are these textures imported from a the CAD package?

It might also be that many cad packages use Z for "up" in the geometry but that change in orientation doesn't always translate to the textures when they get converted. So a front facing plane that had a logo it might now be a front facing plane with the logo being projected from above - hence only showing up on a razor's edge or worse, smearing down across the front face.

It could also be that not all the polys were captured in the select (or they have been reordered on import) and you are either seeing through empty polys, or seeing non textured polys or seeing a pixel from the outside edge of the texture mapping dead center on the model.



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Steve Bentley
Re: GI flicker wont go away.. tried everything
on Mar 20, 2018 at 8:08:37 am

can you upload a little movie of the effect? We might be able to say "oh I know what that is" once we've seen it.



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Justin Thomson
Re: GI flicker wont go away.. tried everything
on Mar 20, 2018 at 2:55:27 pm
Last Edited By Justin Thomson on Mar 20, 2018 at 3:07:48 pm

Could it be the model itself? It looks pretty messy, anyway you could upload it? *Edit sry I did not read your earlier post


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Steve Bentley
Re: GI flicker wont go away.. tried everything
on Mar 20, 2018 at 6:34:02 pm

I think Justin is right - when I first looked I thought I could see through the model and hence those crossing lines were lines on the back faces. But on further inspection it looks like you have overlapping faces inhabiting the same planes. C4D will randomly pick which face is most forward resulting in a sparkling look.



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