Phantom surfaces in VRay render from Grasshopper

[Iain]

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.

[konstantin_chaos]

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

[Iain]

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?

[konstantin_chaos]

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

[Iain]

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

All the best, Iain.

[Peter.Chaushev]

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.


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

[Iain]

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.

[Iain]

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

Cheers, Iain.

[konstantin_chaos]

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

[Iain]

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

Cheers, Iain.