Flipped normals when i mirror a block

Rhino Rhino for Windows
27

Hi @wim sorry I don’t have a picture for it, but I realize I didn’t explain properly what was happening. As the datasmith export to Twinmotion puts the gumball in the middle of the exported mesh (the tree block), we have created a small flat disc inside the tree blocks acting as a placeholder for substituting the trees for the hight quality trees in Twinmotion.
Those trees are included inside the larger blocks (villas) and those are sometimes mirrored. The small flat disc inside those trees>mirrored villas, appear to have the normal fliped and therefore once substituted in Twinmotion, places the trees upside down

28

Hello @pascal and @wim ,

Is it another one bug with long-long story, which is still not solved in V7 and V8?
Since 2014.
So dissappointing.

30

How can I repeat this?

Thanks,

– Dale

31

Simplest case:

create a Rectangle
ExtrudeCrv Solid=No to create a box without top/bottom
Block with the extruded polysurface as content
Mirror the block to some other position
ExtractRenderMesh on the mirrored block

The extracted render mesh has inverted normals w.r.t. the block it was created from.

32

Hello @dale.

Here is the file attached. And a video to review steps.

  1. Try to BooleanDifference Cylinder (which is a block) from the box. It works as intended.
  2. Mirror the block. Try boolean operation again. Here we are.

It is the same for V8.
Animation (1)
123.3dm (42.0 KB)

1 Like
33

Thanks @Screamer - I’ve logged the issue.

https://mcneel.myjetbrains.com/youtrack/issue/RH-82669

Thanks for reporting.

– Dale

34

Hi Screamer -

RH-82669 is now fixed in internal builds. Note that this is not the same issue as the one originally reported in this thread, which is RH-26525, and which still is open.
-wim

2 Likes
35

RH-26525 is fixed in Rhino 8 Service Release 28 Release Candidate