#inconsistent rendering
6 messages in this thread
I'll try to simplify my problem. My .3DS file is actually about 4.5MB in
size, but I don't know what details matter except those listed below.
1) I created a three dimensional box in AutoCAD. 2) I arrayed the
box vertically about 15 times. 3) I DFX'd OUT the resulting drawing. 4)
I loaded the DXF file into 3D Studio 2.0, with weld set to 0.001 5) I
applied two or three omni lights above the boxes and rendered them.
The problem is that partway up the vertical element, I get triangular
shaped dark areas at the horizontal seams of the boxes. Not at all the
seams, and not at any given vertical repetition. Maybe the seams at rows
five and eleven will have the dark areas.
The vertical element created by the piled-up boxes should be completely
even in color or at least shaded slightly, but what I'm getting is
definitely not desirable. I've checked my geometry and it's OK. Everything
meets mathmatically at the seams with no gaps whatsoever in ACAD.
Any help will be appreciated. I'll provide more info and even upload some
files if you would like.
Thanks -Joe Miller
Joe,
Do you get the same problem forcing 2-sided rendering – could be the
result of flipped normals.
Kevin Krell – Computer Support Associates
Kevin:
The darkening he's seeing is like one of the surfaces is at an
angle, and catching a shadow. Like this:
______________ ______________
| | |\ |
| | | \ |
| | | \ |
| | render | \ |
|————–| ———-> |————–|
| | | |
| | | |
| | | |
|______________| |______________|
Two polygons Upper polygon has diagonal shadow
Evan,
While flipped normals are a possibility (remember, there's a lot of
use of triangles, here), Gary's suggestion of setting the smoothing group
would work if that is not the case, unless there is some duplicate geometry
stacked up.
Kevin Krell – Computer Support Associates
You can apply a two-sided material to the boxes to compensate for flipped
face normals, or display, geometry, all lines and see if the black
triangles conform to any of those faces. If so, do a surface, normal, face
flip. This is a little tedious but it can avoid the need for a 2-sided
material which is double the rendering for those faces you apply it to.
This definitely sounds like a smoothing group problem. Note that using
2-sided faces will NOT solve this problem, because smoothing is dependant
upon the surface normals facing the _same way_ for smooth-shading to happen
within a smoothing group.
If you use a 1-sided material, and the surface normals are facing the same
way, try this:
– Under Surface/Smoothing/Object, clear all smoothing groups. – Then, do an
AutoSmooth on that object.
If this doesn't solve your problem, you've either got double faces in that
area or some other geometric anomoly.
– G