#Flashing Faces
16 messages in this thread
Gary,
Recently on 2 separate animations I've all of a sudden started developing a
phenomenon I can only describe as flashing faces. In one case, it's a house
where the soffit or the surface under the overhang has a couple of separate
faces that decide to flash a couple, 3, 4 times over the course of a 500 frame
animation. I've played with smoothing groups, gone in to try to make sure
there aren't any duplicate faces. There are only 2 keys in the entire
animation. Both are camera moves. No light keys. One shadowcasting spot
overhead to simulate the sun. One non-shadowcasting light at about an equal
angle underneath to simulate a reflected light. I'm really puzzled. Got any
hints what might cause a face just to go blooey all of a sudden? Maybe
something I could have screwed up in the set file? Help! I've rendered this
thing 4 times at 15 hours apiece.
Roger D.
Hi Roger,
<< .. developing a phenomenon I can only describe as flashing faces. … Both
are camera moves >>
How close is the camera coming to the objects that display this effect?
When you view one of the files where the effect occurs, describe what you see,
is the texture map missing from the face(s) or is the texture map distorted?
jonas[adesk]
Hi Jonas
<<..How close is the camera coming to the objects that display this effect?..>>
96-Units. ..?..
<<..is the texture map missing from the face(s) ..>> no texture map, one-sided
Phong material. ..?..
Roger D.
There are almost always one of two reasons for flashing faces:
1) Coplanar geometry imported from a CAD program.
2) Shadow-mapped light sources with shadow maps that don't have
enough resolution.
Did you get the geometry from a CAD system or did you make it with 3DS? And…
are you using shadow-mapped lights?
– G
Gary,
The offending piece was created inside Studio. It appears as though it was all
smoothing group problems. I'm going to have to go back and read up on
smoothing groups, but a flat surface consisting of 6 faces should all fall
within the same smoothing group, shouldn't it? Whenever I autosmooth this
thing, it puts the same surface in 3 different smoothing groups. Somehow this
is what the problem seems to be. One of the faces that's in a different
smoothing group than the one next to it all of a sudden flashes every once in a
while. I do have the shadow map size down to about 600, but I ran it all the
way up to 2000 with the same results. Also it wasn't just autosmooth. This
piece lofted like that. It's not exactly a real complex piece of geometry.
It's just basically a square, flat cube with a notch out of the middle of one
side. The whole underside only consists of 6 faces. Like I said, the only way
I can get it to render is to remove all smoothing completely. ?????
Roger D.
From your message to Alan, it sounds like you found some coplanar faces in
there. Is that true?
– G
Roger,
Was this mesh imported from Acad (DXF). I'd like to know cause it has happened
to me too.
-Kouros
Kouros,
See my message to Gary regarding smoothing groups. That's one of the major
problems I've had with Autocad imports also.
Roger D.
In addition to what Gary has mentioned, Roger, I have had the flashing face
problem a couple of times with objects that have been through a few Boolean
operations.
The more typical problems I've had after boolean ops are the occasional flat
face which doesn't always render the same as it's co-planar brothers, and
Auto-Smooth just doesn't seem to work. In these cases, I've detached *just the
surface invloved* as a seperate object, done the Auto-Smooth op (try different
settings and check with the real-time renderer in Optimize.PXP, if you've got
it), and re-attached. It has worked well this way for me.
Once, by mistake, I partially cut off a rounded corner with a flat Boolean
subtraction, and the renderer would flash the face as if it wasn't sure if the
surface was smoothed or a hard corner. I re-booleaned the area with a proper
amount of curvature, and it rendered fine.
Hope this helps a little,
-Alan
Thanks, Alan. Shortly after I posted the last message, I did find some
co-planar faces that I swear I have no idea how they got there. But I have
been working on and off with this thing for a couple of months, so who knows?
I found them by selecting the faces that should be there, splitting them off,
and looking at what was left. There were three faces that basically just
formed an edge to the object. I deleted those, and now Autosmooth works
properly. It was taking up multiple smoothing groups to do one flat plane.
Now it's only one. Wouldn't it be cool to have a check object for co-planar
faces button? Or delete co-planar faces? Thanks, Alan, and everyone else.
Roger D.
Ah ha! There were coplanar faces… (I knew it.)
– G
A) Will Optimize remove coplanar faces?
B) Isn't the DXF import routine in R3 supposed to weed out redundant faces?
-Donald
Hi Donald,
<< A) Will Optimize remove coplanar faces? >>
I don't think so.
<< B) Isn't the DXF import routine in R3 supposed to weed out redundant faces?
>>
It welds coincident vertices based on the WELD-THRESHHOLD parameter (pg 3-38
ref.man.), not faces.
I thought a post talked about Optimize removing coplaner faces with a setting
of "one in the bais" or somthing . I too would like to know if this will
work…
-Brandon
Cyberdreams..
<< I thought a post talked about Optimize removing coplaner faces with a
setting of "one in the bais" or somthing >>
The Bias parameter is used to prevent long thin faces (slivers). The range is
0-1.
See pg 39. of your Disk #7 manual.
jonas[adesk]
The best way to remove coplanar faces in 3DSr3 is to import the DXF file with
the REMOVE-DOUBLE-FACES switch ON. If you've got a 3DS model that you'd like
to do this to, export it as a DXF and then re-import it. The Optimize PXP,
however, only optimizes geometry… it doesn't look for double faces.
– G