When I iray render a simple object I get white blotches. when it is more complex I get light and dark blotches.

Does anyone know how to fix this?

Craig

More prop details would not hurt Crag. Is it an iClone 3D cube? Or something you have imported?

This is a box that I made in sketchup and brought in through xchange then into iclone 7 and rendered in iray.
All of the models that I made in SketchUp have the same issue.

Craig

When you imported the model into 3DXchange did you click "Exclude SKP Back Faces" before exporting it to iClone?

Gerry

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System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.

I just did a quick test to show the difference.

The Box on the Left was exported to iClone with both Front and Back Faces, the same Box on the right had the Back Faces removed in 3DXchange before exporting:





Gerry

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System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.

I think the problem has something to do with cutting holes in surfaces. As long as there are no holes the model renders OK. But as soon as I put an opening on a surface the render gets messed up. 
I have rendered the object without backfaces, with backfaces, with 2 sides turned on and 2 sides turned off.

I also have imported into DAZ and have similar results. It must be something to do with sketchup. If I figure it out I will let you guys know.

If anyone else knows how to fix this please share it.

Thanks, Craig

Craig, Iray respects a *clean* geometry and will not tolerate 2 faces occupying the same space, such as produced by SketchUp.
Wires already presented a solution. Not much else you can do about it.
I do not work with SketchUp, but I download a lot from 3D warehouse.
And removing back faces before importing models into iClone is a standard routine, which should normally be followed (Iray or not).

The other way I often go with (mostly on complex models with sloppy modelling, where materials are not assigned uniformly) is,
import all into Blender, merge front and back faces, then clean double vertices and fix normals.

I found a workaround that seems to work. I export the Sketchup model as an FBX then import the FBX into xchange and then to iclone. 

It seems as though models textured in sketchup create the problem when imported as a .skp file. 

I attached a very complex model that I exported from Sketchup as an FBX. Some of the materials are from iray others are from the sketchup model via the FBX conversion. I had to get a plugin from http://www.simlab-soft.com/3d-plugins/FBX_Exporter_For_Sketchup-main.aspx for Sketchup to make it work. What is strange is that some complex models from sketchup look fine while others look like garbage. Eliminating the back face cuts the size down but it did not affect the iray render. For instance, this car model has all the back faces. Go figure? BTW I was messing around with the headlights. That is why they are screwed up.

When I get the details and a good workflow I will share it with you guys. 

Thanks, for all your ideas.
Craig
 
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Here is a more complicated model. I built it in Sketchup and exported it as an FBX then imported into xchange and then iclone. I replaced the metal with the chrome mdl, the yellow paint and the window with tempered glass mdl. The signage is from images I downloaded from the Internet and put them on the model. Overall I think this workflow is turning out to be quite nice.

This is just an experiment so when I get around to the final version I will post it again.

Hi all,

Please find the far information about how does Iray deal with back facing and overlapping meshes.
https://kb.reallusion.com/Product/52762/How-does-Iray-deal-with-back-facing-or-overlapping-meshes-v11


Thanks
Can(RL)