Phantom surfaces in VRay render from Grasshopper

V-Ray V-Ray for Rhino Issues
1

I’ve been trying to get to grips with Grasshopper and V-Ray recently. Mostly it’s going well but I’ve found one issue that I haven’t been able to resolve - V-Ray seems to be adding extra surfaces that shouldn’t be there. They only appear in the render, not the Grasshopper preview, so I’m guessing its a V-Ray issue rather than Grasshopper.

Can anyone give me some tips to resolve this? I am more or less a beginner with Grasshopper so it is possible I’ve overlooked something obvious. Thanks in advance.

GH VRay Issue.jpg
GH VRay Issue.jpg933×536 77.4 KB

2

Hi @Iain ,

We have not heard of such issues and can’t pinpoint the cause only looking at the two images.
Please share the definition and we’ll take a closer look.

Thank you in advance,
Konstantin

3

Hi Konstantin,

Thanks for your reply and offer to take a closer look. I’ve tried to attach the Grasshopper definition but get a message telling me I’m not allowed to upload a *.gh file. Same thing when I try and to private message. Can I send it via email?

4

Hi Iain,

You can send it via https://support.chaos.com/hc/en-us/requests/new or a file-sharing service of your choice.

Konstantin

5

Thanks for your guidance, Konstantin. I’ve submitted a ticket so hopefully a solution can be found.

All the best, Iain.

6

Hello, @Iain ,
Thank you for supplying the .gh file!
The issue you illustrated comes from Rhino’s API which automatically returns a brep with 4 points from 3-point surface inputs.
For this reason V-Ray needs to have surface output manually processed through brep components. In most cases, directing the Surface output into a Mesh node should do the trick.
If you are unsatisfied with the resulting mesh quality, use a Mesh Brep node instead and hook up a “Settings (Quality)” node to it.

surface_input_to_mesh_brep_example.jpg
surface_input_to_mesh_brep_example.jpg1049×477 89.9 KB

We hope to have this workflow improved in an upcoming v5.2 hotfix dropping the need of manually adding extra mesh nodes.

Kind regards,
Peter

7

Hi Peter,

Thanks very much for the explanation and solution. That makes perfect sense in hindsight, that the whole four sided surface is showing.

I shall give it a try this morning.

Best wishes, Iain.

8

That worked perfectly - thanks again for the solution, Peter. I would never have worked that out for myself!

Cheers, Iain.

9

Hi,

There is a new stable build uploaded here - https://nightlies.chaosgroup.com/mai…table/20211112
You can download it and test if your Grasshopper definition renders fine without the workaround.

Thank you in advance,
Konstantin

10

Thanks, Konstantin. That new build works without the mesh component. Thanks for being so responsive.

Cheers, Iain.