#Info Needed
13 messages in this thread
If anyone has some tips or advice regarding all issues pertaining to
creating/using DXF output from another 3D application -> to import into 3D
Studio, I would greatly appreciate hearing it.
Thanks,
BILL
I'm by no means an expert in this area, but here are a couple of tips:
o Be aware that the .DXF format does not define what is the "outside"
surface. This of course is done in 3DS by assigning a "normal" to one
side of a face (normals can be flipped). So, sometimes after importing
a mesh via .DXF into 3DS you'll see black "holes" where 3DS guessed
wrong as to what was suppose to be the outside. These holes can be fixed
by flipping the normals on the selected faces or just using a two-side
material!
o Also, some programs have a hard time creating a .DXF mesh that has
continuous surfaces where there are suppose to be–I'm trying to say
that sometimes you will get "rips" or gaps along a seem. Basically,
the output program may make two vertices close to each other where there
should be only one. To correct this problem one must weld the vertices
together. Be sure to do this before you apply mapping though, welding
removes mapping coordinates.
All for now. Good luck.
-Dave
Dave:
>> Be aware that the .DXF format does not define what is the "outside" >>
surface. This of course is done in 3DS by assigning a "normal" to one >> side
of a face…
Well, yes and no! <g> There is no "inside" or "outside" of any face defined,
but every face has a normal (or in some cases an abnormal, but that depends on
your model! <g>)
If you remember the "right hand rule" from high school, that will determine
which way the normal is facing. 3DS renders every face which has the normal
facing the camera, and ignores the others unless you have "force 2 sided"
rendering turned on or assign a 2 sided material to the object in question.
Your response was basically correct, I just wanted to clarify why!
Greg Pyros
Thanks Dave. I appreciate the input.
BILL
Bill:
I bring .dxf geometry into 3DS from a CAD program called MicroGDS. I find that
when I create geometry using a solid modeller there are certain techniques
which cause trouble in 3DS. When I punch holes in solids and do many boolean
subtraction operations on a solid the resulting mesh may not import at all or I
get "Invalid Rat Nest" or "Invalid Mesh Object – Can't Cap" messages all over
the place. I have also gotten a "Bright Face" phenomena which may be related
to the non-unified normal issue which is also prevalent.
Bob
Hi Robert,
Thanks for the information. Are there any techniques you have come up with
which allows Boolean-operated objects to import with minimal problems ?
I've never had much luck, but haven't tried to come up with a workaround
either.
BILL
Bill:
Actually, further boolean operations can solve a problem or two. An example
would be a simple window frame. If it was created by carving a rectangular
hole out of a rectangular prism then you may have luck bringing in the geometry
to 3DS by slicing the continuous frame with one more boolean subtract to create
a discontinuity or a break in the donut if you will. I usually just avoid the
boolean subtract altogether and model 4 rectangular pieces. If you create a
concavity by a boolean subtract then you may have a problem on import. If you
just hack away on a solid with boolean subtractions then you should be O.K.
This has been all trial and error for me so I'm as interested in any tips on
this subject as well.
Bob
Hi Robert,
Thanks a lot for the info. This is the kind of stuff I'm looking for if you
have any more <g>. BTW, did you mean "concave" polygon ? Or perhaps non-planar
polygon ?
Regards,
BILL
Bill:
On the issue of concave solids I think an example best illustrates the problem
that I have had.
Say you had a cube 2'x2'x2' and lined up a sphere with a radius of 6" to be
half embedded in the center of one side of the cube. If you then boolean
subtracted the shere from the cube you would have a resultant cube with a
hemishperical dimple on one side. This solid shape with the concave dimple
when brought into 3DS causes a problem for me. If I create concave geometry
(such as a goblet) by surface of revolution means then I usually can bring the
mesh into 3ds. I can't say for sure that all solids which have a concave
surface resulting from a boolean subtract will fail to import into 3ds but in
practice I'm currently avoiding this modelling technique due to failures I have
experience.
Bob
Thanks Bob. BTW, have you ever been able to repair a surface such as that
inside 3DS ?
Regards,
BILL
Bill:
When one of these concave objects causes a problem it becomes impossible to
even load into 3ds. I have had one exception, one "donut" object actually came
into 3DS but I also got an extra face which cut off half of the rectangular
hole. I didn't mess with it since an identical copy of the object came across
without a problem. Its the seemingly random nature of this one exception that
keeps me trying different options and never saying never. These successful
"donut" objects were not created with a boolean subtraction but by extruding
two concentric rectangular loops, just want to make sure you get the whole
picture. Boulean or extruded, I avoid this type of geometry in my solid
modelling only because I can't predict if it will be importable to 3DS. I tend
to keep the solids simple and model up a bunch of simple pieces instead of one
complex whole.
Bob
I've successfully imported Infini-D DXF (Mac) files into 3DS. I had trouble at
first but followed a suggestion from a fellow CompuServe/InterNET animator to
edit out a couple lines from the DXF file. I deleted two lines and it opened
fine.
There is a problem w/ disappearing faces, much like what I read about when
importing from AutoCAD.
Thanks for the input Wade.
BILL