Trouble Displaying Meshes and Breps at the Same Time

Hello Wonderful Developers of Grasshopper!

I have noticed a peculiarity in the display output in the Rhino scene when there are both meshes and breps previewing in the scene. Below you can see an image of some Breps of a box with the preview on and a chart that I coded in GHPython. The chart has its bars and text that being output as colored meshes. However, you can see from the two images below that the mesh can only be previewed from one side (the direction that the normals of the mesh are facing).

However, when I turn the preview of the brep off such that there are no Breps displaying in the Rhino scene, I can see the mesh from both sides:

The weirdest part of the issue is that, if I turn the preview on of the same brep geometry but use a grasshopper preview component that was placed on the canvass after the component that generates the meshes, everything works fine.

I would very much like to be able to always see the meshes from both sides and the breps at the same time. Is this something that is in the works to fix this or is there a decent work-around for the time being?

I have attached the GH file that illustrates the issue.

Thanks, as always,

-Chris

Attachments:

Breps_Meshes_Preview Error.gh, 73 KB

Replies to This Discussion

Permalink Reply by David Rutten on December 6, 2014 at 2:21am

Hi Chris,

this is the first I've heard of this bug. Somehow the open meshes are drawn with normal culling on, which means only the front-faces of the triangles are drawn. Typically closed meshes are always drawn this way, it's both faster and it doesn't result in wrong pixels near sharp silhouettes. Somehow the culling flag isn't set correctly.

If this bug requires changes in Rhino5 code then it probably won't be fixed in R5, as development has been halted.

I've installed both LadyBug and Python to be able to open your file, but I'm still getting errors.

Can you perhaps internalise the meshes and breps and post a GH file without any special components?

Permalink Reply by Chris Mackey on December 6, 2014 at 3:52pm

Hi David,

Thank you so much for the quick response and sorry about the GH file. I had failed to realize that my Python tuples would not be correct internalized in the GH "Data" component. The attached GH file should show you the error correctly on you machine.

Thanks again,

-Chris

Attachments:

Breps_Meshes_Preview Error2.gh, 71 KB

Permalink Reply by Chris Mackey on December 7, 2014 at 2:54pm

David,

I just noticed that you had requested a file without any special components and, attached you can see the issue using data internalized in native GH components. There's a chance that the error might go all of the way back to how I generated the meshes with RhinoCommon so you have the original code and method of generation in the previous file if that is where the problem is. Specifically, the meshes are generated with the RhinoCommon Rhino.Geometry.Mesh.CreateFromBrep(Brep) method. If the mesh generation is where the problem is located, it might be a good idea to post this issue to the GHPython category instead of here. The issue just seemed so related to the order of components on the canvass and I could imagine other ways of making single-sided meshes in GH that I decided to post it here initially.

Let me know if there is anything else that I can do to expedite the identification of the error.

Also, I forgot to say thank you for the explanation about the normal culling. It makes sense and I can see how it is useful.

-Chris

Attachments:

Breps_Meshes_Preview Error3.gh, 298 KB

Permalink Reply by Dimitrios Papadopoulos on February 10, 2015 at 1:02pm

Chris and David,

I am currently having a similar problem.

Not sure if it s the latest Rhino Update (5.10.41201.11145, 12/01/2014) or very latest GH,LB,HB update, because I am sure I could see both faces rendered properly 1 month ago in the same file.

I attach the relevant file.

Have you found any solution to this?

Thanks,

Dimitris

Attachments:

Forward_Raytracing_01.gh, 438 KB

Permalink Reply by Dimitrios Papadopoulos on February 10, 2015 at 1:04pm

I also attach two images.

dimitris

Attachments:

Imd_1.JPG, 268 KB
Imd_2.JPG, 211 KB

Permalink Reply by Chris Mackey on February 11, 2015 at 1:12pm

Dimitrios,

There's no solution I know of yet except to turn the preview off on the breps. I also remember never experiencing this problem a few versions ago.

I have edited a lot of the Ladybug and Honeybee components to try to make meshes appear in the usually more desired direction and, in the images that you post, I know that you can flip your starting brep and that should make the final mesh colors appear on the side you want.

Hopefully, GH team has a response for us soon.

-Chris

Permalink Reply by Dimitrios Papadopoulos on February 11, 2015 at 1:19pm

Thanks a lot Chris!

I ll go around it for the time being.

Dimitris

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