BlendEdge bug - rolling ball

Hi McNeel
I’ve been seeing this a couple of times, so here’s an example. When BlendEdge goes across tangent edges, it feels compelled to create strange patches, that dip rather than just continue across as seen on the V6 example. It looks as if it tries to create sort of a corner blend, but there’s no corner there - the sides are completely tangent (also according to EdgeContinuity). In this case it happens with a radius of 1mm, but not at 0.5mm. Other incidents have had it happen with other values. Just to see if it’s a “tangency vs curvature” thing, I made a shape with a curvature continuous transition/arc - same problem (the last shape marked Curvature). In that case 1mm works, but it makes the patches at 1.2mm. Is it my modelling and what should I do to avoid these weird, dipping areas - or is it simply a bug in the BlendEdge code?
Blendedge bug.3dm (18.8 MB)

Sysinfo in case it matters (I’m still on the last beta)
Rhino 7 SR0 2020-11-4 (Rhino 7 BETA, 7.0.20309.06003, Git hash:master @ 368ab021c8426434a95c36999f545f918e04df2c)
License type: Commercial, build 2020-11-04
License details: Cloud Zoo
Expires on: 2020-12-19

Windows 10.0 SR0.0 or greater (Physical RAM: 95Gb)

Non-hybrid graphics.
Primary display and OpenGL: NVIDIA Quadro RTX 4000 (NVidia) Memory: 8GB, Driver date: 9-22-2020 (M-D-Y). OpenGL Ver: 4.6.0 NVIDIA 452.39

OpenGL Settings
Safe mode: Off
Use accelerated hardware modes: On
Redraw scene when viewports are exposed: On

Anti-alias mode: 4x
Mip Map Filtering: Linear
Anisotropic Filtering Mode: Height

Vendor Name: NVIDIA Corporation
Render version: 4.6
Shading Language: 4.60 NVIDIA
Driver Date: 9-22-2020
Driver Version:
Maximum Texture size: 32768 x 32768
Z-Buffer depth: 24 bits
Maximum Viewport size: 32768 x 32768
Total Video Memory: 8 GB

Rhino plugins that do not ship with Rhino
D:\Dropbox\2D & 3D\GH\elefront421\ElefrontProperties.rhp “ElefrontProperties”
C:\ProgramData\McNeel\Rhinoceros\7.0\Plug-ins\Twinmotion Direct Link 2020.2 (e24ee14a-9514-47da-8fe6-f6e61b20160e)\Twinmotion Direct Link 2020.rhp “Twinmotion Direct Link 2020”
C:\Users\jn\AppData\Roaming\McNeel\Rhinoceros\packages\7.0\NVIDIADenoiser\0.1\NVIDIADenoiser.Windows.rhp “NVIDIADenoiser.Windows”

Rhino plugins that ship with Rhino
C:\Program Files\Rhino 7 WIP\Plug-ins\Commands.rhp “Commands” 7.0.20309.6003
C:\Program Files\Rhino 7 WIP\Plug-ins\rdk.rhp “Renderer Development Kit”
C:\Program Files\Rhino 7 WIP\Plug-ins\RhinoRenderCycles.rhp “Rhino Render” 7.0.20309.6003
C:\Program Files\Rhino 7 WIP\Plug-ins\rdk_etoui.rhp “RDK_EtoUI” 7.0.20309.6003
C:\Program Files\Rhino 7 WIP\Plug-ins\rdk_ui.rhp “Renderer Development Kit UI”
C:\Program Files\Rhino 7 WIP\Plug-ins\NamedSnapshots.rhp “Snapshots”
C:\Program Files\Rhino 7 WIP\Plug-ins\RhinoCycles.rhp “RhinoCycles” 7.0.20309.6003
C:\Program Files\Rhino 7 WIP\Plug-ins\Toolbars\Toolbars.rhp “Toolbars” 7.0.20309.6003
C:\Program Files\Rhino 7 WIP\Plug-ins\3dxrhino.rhp “3Dconnexion 3D Mouse”
C:\Program Files\Rhino 7 WIP\Plug-ins\Displacement.rhp “Displacement”

OK, just discovered something else. If you zoom in on the V7 version, you’ll see that the trim curve of the upper surface is… weird. Blendedge on such a simple shape shouldn’t cause such a weird result. I really hope this is something that can be fixed - I would hate V7 to be a step back in terms of realiability for FilletEdge and BlendEdge!


OK, so talking to myself here :slight_smile: One solution is to create the smaller shape without splitting at the tangents and moving the seam - but that’s another can of worms. Would be nice, it it just worked.

1 Like

Hi @pascal
Sorry to drag you into this, but I have no idea who else to call on. Could you put this to the attention of whomever would be resposible, since there’s been no response?
TIA, Jakob