28-02-2005, 06:27 PM
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#1 |
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Registered Member
Join Date: Aug 2004
Location: Abilene, Texas
Posts: 10
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Cutting holes in cylinders problem
I need a book on basic poly modeling or a web site on the subject. keep running into modeling problems I can't solve when working with poly modeling and subdividion.
For example: when I try to cut a circle in a cylinder, and then subdivide it, it gets all twisted up. I am just not sure how to approach this problem. Does this mean you can't do any cutting until you finish subdividing the model? I can delete faces just fine, it's circles and joining tubes at right angles that seems to cause my problems. Kori |
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28-02-2005, 09:25 PM
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#2 |
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Super Moderator
Join Date: Jan 2003
Location: Sunbury, UK
Posts: 2,339
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The problem you're getting is because a subdivision surface can only have polygons that consist of three or four vertices. Therefore when cutting using booleans, you have to be a little careful on the resulting geometry. The other thing you need to be careful of is the fact that a subdivision surface is the limit surface produced by a spline approximation to the control cage defined by the polygon mesh.
What this means is that in order to maintain the shape when deleting or joining geometry, you need to add further geometry around that point. For instance, if joining two cylinders at right angles, then try preforming a couple of bandsaw operations around the joint to add definition. Hope this helps. |
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09-03-2005, 06:07 AM
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#3 |
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Full Access Member
Join Date: Mar 2003
Location: Sarpsborg/NORWAY
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Maybe stupid quest, but where do want that hole - sides or ends?
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09-03-2005, 02:39 PM
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#4 |
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Registered Member
Join Date: Aug 2004
Location: Abilene, Texas
Posts: 10
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In the side. This is an example, not the model I am working on. When I cut a hole in the side of a cylinder and try to bevel it or extrude it, weird things happen.
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09-03-2005, 08:27 PM
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#5 |
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Full Access Member
Join Date: Mar 2003
Location: Sarpsborg/NORWAY
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The easiest way is to stensil a disk to the sylinder (with # of points = the points "surrounding" the stensil) . Then select the polys surrounding the disk and KILL it (K). Delete the points you don't need to form the stensil. Then make new 4 p polys "around " the stensiled points. You see ?
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09-03-2005, 08:29 PM
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#6 |
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Full Access Member
Join Date: Mar 2003
Location: Sarpsborg/NORWAY
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More pics
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09-03-2005, 08:31 PM
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#7 |
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Full Access Member
Join Date: Mar 2003
Location: Sarpsborg/NORWAY
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and one more...
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10-03-2005, 12:09 AM
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#8 |
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Registered Member
Join Date: Aug 2004
Location: Abilene, Texas
Posts: 10
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bjørn
Thanks for the information. As you can see in the image below, your instructions worked, and the cut hole is clean. I see now that I needed to 'match up' the vertex number of the hole to the vertex number of the surrounding polys, to make quads around the hole. Thanks Kori 
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10-03-2005, 09:04 PM
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#9 |
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Full Access Member
Join Date: Mar 2003
Location: Sarpsborg/NORWAY
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Happy to be able to give something back to this superb forum.
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25-03-2005, 03:31 PM
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#10 |
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Full Access Member
Join Date: Jan 2005
Location: Madrid / SPAIN
Posts: 28
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Hey, nice trick. I will use it from now on.
 Regards from Spain Jose |
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