Some polygons shading wierdly

Some polygons shading wierdly

by Matt Maxwell

on Aug 15, 2014 at 1:51:09 pm

I'm pretty new to C4D and the client gave me an OBJ model. When I render I'm getting visible unwanted lighter shading between some edges. See the attached grabs showing the mesh and the improperly shaded areas.

I have tried optimizing the geometry and experimented with other mesh commands (that are mysterious to me and seem to create uneven results, but I believe that the problem isnt the mesh, but the few triangles that are shading incorrectly. And the client is very picky and I cant have a lumpy surface.

Please help if you can. I need these to render without these edges showing!

The problem render:

The wireframe:

Wireframe zoomed out (for context):

Another view close-up (click to zoom in for a better view):

Re: Some polygons shading wierdly

by Brian Jones

on Aug 15, 2014 at 3:28:27 pm

no triangles would be better. Try selecting all the points and run an Optimize, then select all the polys and Align Normals (and make sure they are all facing outwards), then try to Untriangulate - you'd have to play with the settings to get as many as possible to change to quads and you won't likely get all of them - it might not be necessary anyway. if it is it might take doing it by hand

Re: Some polygons shading wierdly

by Matt Maxwell

on Aug 18, 2014 at 10:05:40 pm

Thank you for your response. It helped me get closer. The mesh was a nasty mess with all sorts of redundant points. I optimized and de-triangulated, Much nicer. But I still have shading issues.

The polygons that are shading incorrectly have little white lines pointing in the wrong direction. I am assuming that these little white lines represent the direction that the light will bounce. See attached. Note the few polys that have white lines that don't point in the right direction.

How can I make these problem little white lines point correctly? I have tried deleting one of the problem polys and recreating it but when I create the new poly, its white line does the same thing.

Re: Some polygons shading wierdly

by Brian Jones

on Aug 19, 2014 at 1:14:07 am

the white lines are the representation of the 'surface normal' the not necessarily the direction light will bounce (since that depends on the angle the light originates from) but the average direction the polygon is facing. Your problem polygons appear to be coming from the diagonal lines in those upper polys that are not untiangulated. In poly mode normals won't show unless a poly is there so the 'line' has to be a very skinny poly. The upper. larger polys with the wider/thinner chunks should be deleted and the the thinner one below it with the three (at least) polys deleted as well then use the make poly tool to add two polys, one thin one below matching the others below it and on larger one on the top (well top in the picture anyway).