Loft and Sweep ends incorrectly displaying

Grasshopper
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1

I experienced a new display issue with lofts and sweeps that makes 2 bands at the start and at end of the sweep appear rounded instead of sharp. If you apply a swatch with the custom display component to these sweeps you get zebra stripping appear mixed in with the color. No matter the complexity of the curve, this only appears at the extreme edges of the sweep or loft.

I am creating the lofts/sweeps directly from a set of curve shapes wither using Brep.FromLoft(); or Brep.FromSweep(); then I pass the Brep out of the component. I tried exploding the geometry to check for any errors but the geo seems fine. It just doesn’t display correctly.

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When I bake the geometry and reference this issue stops existing.

2

try explode brep → brep join and preview that

1 Like
3

Thanks, had not tried that, this does fix the preview. Rejoining the Brep after exploding recreates the problem.

I would like to understand why this is happening to avoid it from happening. Is this a UV mapping issue?

I noticed that if I create a bounding box around the object and do solid intersection it resolves the problem. what operation in the solid intersection component fixes the preview of the brep?

4

Having a similar issue, with a similar solution. This must be a relatively new bug in 8.14.24317, since I haven’t experienced it before in all updates up to 8.9.

1 Like
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@Kane_Borg - can you post some simple .gh file that demonstrates the problem?

– Dale

6

Hi @dale sure thing, see below minified example. It’s easy to replicate any profiles lofted on any curve type (I think even if swept) will create this issue, when planar capped. extruded curves do not visibly show the issue, only profiles with sharp creases will show the extremity bands. Maybe an issue with the display mesh normals?

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(My current Rhino version Version 8 SR11
(8.11.24254.15001, 2024-09-10))
example file (7.4 KB)

7

Hi @Kane_Borg,

I’ve updated your C# code - please review.

example issue with display artifact.gh (5.1 KB)

– Dale

8

Hi Dale, didn’t know that Brep.Faces.SplitKinkyFaces would effect the edges of the loft in this way. Thanks for the insight.
Should this check be added to the default behavior when capping or is it by design working like this to cater for other edge cases?

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@dale One issue though is that the elements will now display the brep edges as shown above when rendered. Any way to circumvent this? Also the draw speed is increased by a couple of milliseconds when calling args.Display.DrawBrepShaded(brep, material).