#Boolean help needed
16 messages in this thread
I have a pipe, made out of two cylinders stuck together, one smaller than the
other, and revealing itself inside the larger one. (easy way to do 2 textures)
Now I'm trying to chop them up some. One I'm trying to cut in half, like a c
shaped pipe- half missing. The other I'm trying to cut the top off at an
angle.
I tried cutting the pipes apart with a basic cube, but it kept giving me
errors. I moved it about alot, and consulted the manuals.
I then made a higher detail polygon count cube using the grid IPAS. lots of
little polygons in that sucker, I forget how many. I tried it again, and it
kept giving errors.
I then proceded to make a text cylinder, with more parts to it along the length
of the pipe. I tried the subtraction boolean again, and no go.
Somehow I finally got a strange result (mabe on the last way I talked about, I
forget)- it was the half pipe, with one single plane left from the cube. I
don't understand it, so I thought I'd ask here. I know there were probably
many planes made up in that grid/cube type object, but I figured at least one
would get it. 🙂 I didn't know how to get a 6 sided, lots of polygons, cube
to use as a subtractor. Any pointers? I realize I'm not the polygon guru
here, and probably missed something really simple. (but I thought booleans
would be simple, if they worked..) The pipes look great, so I'd like to cut up
what I have now, instead of recreating them, if possible.
Thanks as always,
JNJ
Hello
I am definatly no boolian guru but i have created cubes with lots of polygons
by tesselating in Optimize, which works much better than 3d editor tesselate
because the polys are all in a grid.
Ed
Thanks Ed. I think my problem was different than I expected, the pipe needed
to be built differently. I'm not sure I'll ever really get all the guts of
this stuff. I guess I need digital putty or wood or something. 🙂 Then I'll
take my dremel and drill, etc and a VR goggleset and go to it! That'll be the
day. It won't wake up the neighbors either. 🙂 R5? hehe
JNJ
>>I guess I need digital putty or wood or something…
You may be interested in some software that FARO Technologies is working on for
use with their 3D digitizer. I put some details in another message (#156690)
with a more appropriate subject line.
JKJ
got your other message, looks very interesting.
>>cylinders-cube=???
John N. Jordan,
You said, "like a c shaped pipe" – did you using TUBE or are you using the two
cylinders to make the pipe? Does your pipe have inside and outside walls?
Have you attached something to give more than one element?
I just tried a number of combinations of cylinder and cube subtractions and
didn't have a problem.
Without more info, I can only guess, but if your subtraction object (cube)
crosses more than one element, especially if the elements overlap, the boolean
probably won't work. In this case, simply detach the elements, subtract copies
of the cube, then reattach.
Are you are subtracting a cube from a TUBE? Tubes are often problems for
booleans. If your pipe needs to be a tube (with inner and outer walls), the
cleanest way to cut one is to make it out of two cylinders: make the outside
cylinder to size, make an inside cylinder by scaling the other down in diameter
and up in length. Subtract the cube from the outside cylinder. Rotate the
inside cylinder a little (to keep down problems with coincident edges in the
boolean) and subtract it from the outside cylinder. This should give you a
perfect cut tube.
Note that with R3/4, you almost NEVER need to tesselate before booleaning.
Oh, a BIG step I about forgot: never, never try to boolean with long cylinders!
The culprit is long narrow faces, which the algorithms can't seem to handle
properly (single precision roundoff?). Cylinders (and tubes), due to their
nature, are the worst producer of long narrow faces. When making a long
cylinder (or any LONG object), I always use several segments to produce much
shorter, narrow faces.
If I'm confused about your problem (a high possibility <g>), then clarify or
simply email the 3DS file to me and I'd be glad to look at it. Long live the
bool!
JKJ
JKJ,
You are correct in properly interpreting what I was trying to say. I used the
TUBE, with probably the longest polygons possible between the top and bottom.
(didn't think I'd need that detail) I guess I should've looked into booleans
before I spent all that time getting the texturemapping right. Silly me. And
they look so real. 🙁 Hopefully I can pull off the mapping and reapply them
easily to the rebuilt ones.
I'll probably have to rebuild the 2 cut up pipes, like you mentioned, using
true cylinders and cutting them out with another.
I'll try that, thanks. Great help.
(thanks Jack)
JNJ
<<I guess I should've looked into booleans before I spent all that time getting
the texturemapping right.>>
Yes, it is unfortunate that you will loose the mapping you've done when you
perform a boolean, but there is a way to "safeguard" your mapping:
1) Create a copy of the object you want to retain it's mapping called COPY(for
the purpose of explaining)
2) Hide or freeze this object.
3) Perform the boolean on the original object.
4) Unhide or unfreeze the COPY object.
5) Acquire the mapping coordinates and texture from the COPY object and then
apply this mapping coordinate and texture to the booleaned object. The COPY
object will be in the same position/orientation as your original object so you
will get a perfect copy of your previous mapping.
6) Delete the COPY object.
If the object is too large to warrant a copy then you can use a "surrogate"
object such as a box(you can even use an object consisting of a single vertex).
If you have any more questions let me know.
David "Travelled the world on a spherical map" Gould
David, Just in case you didn't see my message to John. You don't have to copy
the object to keep it's mapping coordinates intact. Just do an Acquire from the
original object first. Then just do your boolean operation. Now go to mapping
and the icon will reappear exactly as it was last left – from the acquire. Just
reapply it and all is well. I use this all the time and it's much more
efficient than having to make a copy. Thought you might like to know this.
DM
Thanks for the reminder about the "Acquire" technique. Though this method is
effective, when you are doing a boolean between several objects and you want to
have the same mapping for the new booleaned components the "Copy and reapply"
method is the only one I can think of at the moment. Have you got any other
ideas on doing this?
David "Ideas welcome by the bagful" Gould
Good tip, David.
-David Swoboda
John, Actually there's even an easier way than DavidG's example of how to
retain your mapping coordinates. Just Acquire the mapping from your object
first. Then do your subtraction or whatever. Now just Go to Mapping and the
icon will appear exactly intact from your previous use. Just apply it back to
your object and go. I use this one all the time, works great.
DM
Thanks David, I haven't time to try out these ideas yet, but hopefully will
late next week. Right now I've got to figure out why my PAR doesn't want to
save from Windows. Sometime it doesn't like me manually copying an appropriate
.tga to it from a dos window! It worked before, but it's messed up. I used to
save static frames out of Picture Publisher all the time, but now it says there
is a write error.. any ideas?
JNJ
John, No, I can't save to the PAR directly from Windows either. I just leave a
DOS window open and I'll save then alt-tab and F3 to keep resaving the image to
tha PAR. I haven't had any corruption when saving from a DOS window though. One
thing that just happened (first time) is I had an animation punt half-way
through and do the table-cloth like thing. I had read a message from Don Landis
stating that the best block limit was 240 (2217A) I set mine at 240 (was at
200) and had some corruption problems. I turned it down to 220 and it's been
fine ever since. Hope you figure your problem out.
DM
Thanks. My problem is that I can't even run the PAR control in Windows.. it
looses my mouse. (Wacom UD-1212 tablet) I haven't played with PIF settings or
anything, mabe I can get it working.. but haven't had time to work on it. I
can't wait for Windows drivers.. but noone seems to know when they'll be out.
I'll finally have time to work on the boolean thing this coming week, crazy.
JNJ
As John K. says, add segments to your cylinder. Those long, narrow faces are
Boolean-killers.
– Jack