koobas.hobune.stream
Why does inverting two components of a normal break them?
I have a tool that is creating a mesh from existing data. This data was created in 3DS Max which uses a right-handed Z-up coordinate system.
When I import the vertices (and normals), I swap the Z & Y components then mirror (invert) the points along the X and Z axis. This works fine with the positions, but the normals become distorted (see the image below).
I cannot see why this is. I have not adapted any transforms or anything else that could be deforming the mesh incorrectly, these are just arrays of absolute positions in space.
If I do not invert the X component, the normals display correctly (although my model is mirrored, and I must apply a scale of [-1,1,1] to have it display correctly). Further, if I do not invert the Z component, but instead apply a scale of [1,1,-1], the model also displays correctly.
This last part confuses me the most - inverting the last component and multiplying by a transform scales it negatively, are equivalent are they not? Why can I invert one component and have the normal work, but not two? What have I missed?
(edit: note the teapot is meant to be tapered, so I can tell what direction its facing all axes) ![alt text][1] [1]: /storage/temp/24054-teapot.jpg
I used to have issues like this with Blender imports, no suggestion on how to fix them ins$$anonymous$$d lesson learned: on Blender FBX EXPORT, set the Y/Z "stuff" to be how Unity expects them and all is well. If you don't get a better Answer, something to try in the meantime...
@getyour411 this is a reply to your comment below (I cannot add a comment to the answer post) - I am trying to accept the answer but it says I do not have permission and must login as another user! (my rep isnt high enough to accept my own answer, perhaps?) Should I convert it to a CW? Or should someone else put the answer down under their name and I can accept that one?
A post on this thread prompted me to find the answer: if you want to do this transformation you have to invert the winding order! The coordinate system change is working now.
Good find, tick the Accept this answer below the thumbs!
