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Boolian Subtraction
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Boolian Subtraction // Archive: Tech Forum
Post by janetb // Jan 8, 2007, 12:12pm
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janetb
Total Posts: 35
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Can't boolian subtract the vertical blocks from the horizontal bar. I finally ended up trying them one by one. It works fine about half way thru and then gets screwy. Tried many different orders, but it always gets weird artifacts after about twelve subtractions. I have included an extra set of parts in the scene.
I have TS 6 and 2KPro.
Janet |
Post by hultek43 // Jan 8, 2007, 1:00pm
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hultek43
Total Posts: 234
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Step 1: union all triangular 'drills' into one object.
Step 2: Select bar then boolean subtraction
Step 3: select drill object. |
Post by prodigy // Jan 8, 2007, 1:27pm
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prodigy
Total Posts: 3029
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This seems to continue till ts7. Paramter setting (right mouse on boolean subtract) makes also a difference. Where I set the two params you get a "destructed" result, but I added the same object after a right click and as one can see the edges of the cuttings look perfect there. So the problem will be the "miss"assignments of edges, vertex and faces streams.
The other one where I just set one param looks better, at least the cutting shapes are there, but the surface looks a little like up and down the hills:confused: This looks a bit to me as if there maybe some kind of settings similar like "show triangles" which has the effekt that the edges that lost a vertex get pointed in a wrong direction. Question to the experts: is there a parameter where yoh can set similar like triangle/suqares ?
If you render.. you see the render its ok..
Thats why i delet my post.. because works without problems.. |
Post by TomG // Jan 8, 2007, 4:12pm
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TomG
Total Posts: 3397
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This is why many modelers call Booleans "evil" as they allow you to come up with complex shapes that look ok (and in the case of the tS offline renderers, are ok since they are very very forgiving about geometry), but which while looking fine are in fact something of a mess.
The problem is that many renderers and engines require faces with no more than 4 vertices. Some require triangles of course, just 3 vertices.
tS does NOT require that, and neither does Lightworks for that matter, so you can work with this sort of shape and not have a problem. The real-time renderers though get confused as they try and interpolate where a face is going - they work out the surface by seeing where it is going between one vertex and the next, and having too many vertices makes a mess of that and some confusion results are to what the normal is on the surface at some particular points.
THis is not an error in the booleans by the way, just the nature of 3D objects and the requirements of engines to have things triangulated for fast and accurate rendering.
You run into the same problems if you try and export to different engines too. And the answer is not to build things quickly using booleans, but to build them in a more controlled fashion by yourself. You ensure you have "extra" edges in there, ones that don't seem to serve any purpose from the point of view of the shape of the object, but they do serve a purpose for the render engine :)
You can also go through and manually add edges to a shape after having used booleans. That's often trickier, though, than just setting out and building it yourself without booleans.
If you don't take those steps, then automatic triangulation kicks in. This often takes one vertex and connects it up with an edge to another vertex. Where you started with a quad face, this works just fine. When you have a face with many vertices, though, it often connects the same vertex to all the others, as seen here. The result is a lot of "long thin" triangles that generally signify you are going to have problems with some engines (real-time, or otherwise).
Some programs don't include booleans at all due to this "evil" nature of letting you get into a real mess with ease. Some programs do include them, but when you see a tutorial, it usually doesn't use booleans :)
HTH!
Tom |
Post by SteveBe // Jan 8, 2007, 4:38pm
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SteveBe
Total Posts: 282
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That's why I've always liked NURBS. You can even bend them later and
they have a nice smooth curve. |
Post by janetb // Jan 10, 2007, 7:11am
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janetb
Total Posts: 35
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Hi Folks...Thanks for your replies....!
I think I have unintentionally misled you---It all works perfectly---IF I am working in Wireframe; or IF my goal is a render. There are no missing edges and it all worked beautifully from the start with ALL the cuts made in one step....
The problem is that I need this to work in Solid mode.....Attached is a picture of the finished piece (I don't know where in the post it will appear---we used to be able to put them in the body of the post).....I want to be able to play with changing the materials back and forth quickly (gold, silver, white gold, etc) and see how it looks with out having to do a render each time. It's more of a working diagram. Even for a final shot to send someone else, I find I get good metal effects with a screen capture of the TS workspace.
So the question actually was how to get it so you can see thru the cutout parts in SOLID mode to the contrasting metal liner which it will be placed over....In Wire mode it is perfect already. In solid mode I was having the same problems as pictured by the other posters....
I tried with just the upper half of the cuts (ie the parts I sent in my original post) using each one indidvidually to see if I could locate a culprit cutter. But each cutter worked fine IF it was one of the first twelve or so cuts. The interesting thing that kept happening over and over was that I started at one end, made cut by cut until there were about twelve perfect cuts, and then on the thirteenth, ALL the former cuts totally disappeared and there was no way to get them back! I tried it first from one end, then again starting from the other end, then again taking cuts from alternate sides. In the first two cases, the earlier cuts disappeared, while in the last case, I got the artifacts like the other posters. If I cut them all at once, I also got the artifacts. It always worked fine up to a certain quantity of cuts, and each of the cutters worked so long as they were done early enough on. So it wasn't the geometry of any of the cutters, and it couldn't be the geometry of the slab because that was just a flattened cube or an extruded plane (I tried both).....
So how can I get to see thru my cuts in solid mode.....?
By the way, an additional problem I thought of is that I forgot to cover the bar with the million vertices that will be needed to bend it into round---that will undoubtedly challenge the boolian cuts, no....?
Another by the way---I did a band ring with cut-out letters a long time ago---that should have been more difficult because of the curves, but it worked...I don't remember if I had any trouble with it.....
Thanks for the input!
Janet in Jerusalem |
Post by janetb // Jan 10, 2007, 7:30am
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janetb
Total Posts: 35
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As soon as I posted that last post, I solved the problem a minute later....:-)....
1) Made all the cuts at once (with boolianed cutters) and then
2) Hit the Triangulate button.....:-)
Now, what's the best way to prepare it to bend into a ring? Please recall that I have TS6, not 7.....
Janet |
Post by Bobbins // Jan 10, 2007, 9:05am
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Bobbins
Total Posts: 506
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There's a tool called "Bend Current Object" that should do what you want. I find it easiest to rotate the object to fit the tool when using it. |
Post by janetb // Jan 19, 2007, 5:48am
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janetb
Total Posts: 35
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There's a tool called "Bend Current Object" that should do what you want. I find it easiest to rotate the object to fit the tool when using it.
The Bend tool will not bend a strip into round unless the strip is first given a lot of vertices perpendicular to the bend---at present it has none....The question in effect was if it is possible to do this after all the cuts have been made....I think not....It would have to be done before the cuts if you want to use the Slice tool (to add parallel vertices). I think the last time I did this (it was a long time ago) I used the Sweep tool to create the strip to get equal increments (Is there a way to get equal increments with the Slice tool?). I just have a feeling that all those vertices would make the cuts more difficult to do afterwards....Either way, this seems like a difficult thing to do with TS...Is there an easy way to do this? I have many such designs that I would like to do models of....
Janet |
Post by Norm // Jan 19, 2007, 6:43am
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Norm
Total Posts: 862
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i believe it boils-down to geometry/density of mesh. If I was to approach the scenario I would create the band first, then I would begin to create the drill objects; object used to punch holes in the band. You could build the drills 360 degrees around the band, boolean union them together and try a single boolean subtract between the band and the drill. Alternately you can rotate the band and punch a pattern from it.
Bend tool distorts geometry and one would expect, so to expect non-bent geometry afterwards is going to lead to frustration.
It is all math and trueSpace should not be left to make decisions on its own. If your drill has a dense enough geometry, the boolean operation should be successful. If not enough geometry is present, you would not see the result you hope to see.
In the case of a ring/band, there are two diameters; id and od. Id is smaller than od, so looking at a cross section of your drill(s), they should have an equal taper to them. This would ensure proper hole is left afterwards.
Not sure what else to say. hmm ... the area of intersection is the most important in my mind. That is where the geometry is required to help the math do a proper job. If you have little lines/edges of intersection along the area, you get funky results.
If you use "Delete Edges" from boolean settings panel, this to me can cause problems as the drill will leave a footprint of its geometry across the area of intersection. Deleting Edges removes this footprint.
You are correct about using bend tool and requiring perpendicular edges. I suggest you also require horizontal edges. I discovered this making some Tiffany Lamp shapes. As I added horizontal divisions I ended up with a smoother end result. So both vertical and horizontal edges are required along the mesh to ensure proper bend of the entire object. But again this will distort depending on degree of bend.
I say boolean are complex rather than "evil" :) |
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