DeleD Community Edition

[chronozphere]

Hey guys

I often want to attach a cylinder to a plane. This can be cumbersome because alot of vertices are involved. Now, I've found a nice workflow to weld a cylinder with a random number of segments to a plane:

1. Make a cylinder and an object you want to weld it to (I made a cube in this case, but it can be anything with a big polygon to put the cylinder through).



Make sure to remove the cylinder cap that sticks inside the cube. We don't need it!

2. Select the polygon of the cube that intersects with the cylinder. This must be one single polygon. Use the extract tool to turn that polygon into a single object. Make sure that "remove original polygons" is checked.

Select all the polygons of the cylinder that intersect with the cube and turn them into one object by using the same method.

3. Now, select the two objects that we just made (the parts of the intersection) and use the Unite CSG command. It should look like this:



4. Notice that the isolated polygon of the cube is now split into a number of small polygons. Select them and do extract again (use remove original polygons). Then use optimize to make the mesh look nicer.

5. You can now merge all objects together (There should be 4 of them).
The merge operation automaticly welds the vertices together, provided you have not moved any of the objects while doing this tutorial.
The result should look like this:



Hope you find this mini-tutorial usefull.

Cheers

Chronozphere

[paul_nicholls]

Hey, neat!

It works, even with LITE

Thanks for sharing

cheers,
Paul
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[AWM Mars]

This looks splendid.

I am a bit confused, when I use the unite operation, I end up with more polygons, edges and vertices then I started with, even when I use Optimise.

Using the method you describe above, what are the Polygon, Edge and Vertice counts, before and after?
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[Jeroen]

I'm probably not seeing it, but I'm a bit confused. If you want to attach a cylinder to a plane, why not only use the Unite CSG tool and use Optimize afterwards? If the cylinder and cube overlap, you get the same results. So why use Extract?

@AWM: you end up with more edges and vertices because the Unite tool (as any CSG tool) creates new polygons. Using Optimize after using CSG is good because, most of the time, it cleans up lots of polygons that are a direct result of CSG.
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[chronozphere]

This is why I don't use CSG directly:




As you can see, a lot of polygons of the big cylinder are split by the CSG operation. Only a few of it's polygons were actually intersecting the small cylinder. I'm not a big fan of DeleD's current CSG because it keeps cutting up your geometry.

Optimize wouldn't be a sollution because it affects your whole object. Let's say you deliberately made a few coplanar adjacent polygons. Those will dissappear as soon as you optimize.

Extracting polygons allows you to keep the rest of your geometry safe from any possible CSG violence.

[Jeroen]

Your new example is clear - I can see why you would use Extract in certain situations. It makes me think that it would be nice to have an Optimize tool that can operate on selected areas of the object only. Much like Smooth does too. I realize that wouldn't help much in this situation, but it's nice to have.

On a sidenote: it's in the nature of CSG routines in general to cut up geometry if you use BSP trees to perform the CSG action (which DeleD does). Using BSP trees speeds up the computation and provides a relatively clean algorithm compared to some other suggestions I've seen (back in 2005). Although DeleD's implementation isn't 100% full-proof, it can compete with packages like Maya (Elementrix mentioned that a while ago) so it ain't half bad.
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[chronozphere]

Maybe I could change the CSG code to automaticly select the intersected polygons of both objects and operate on only them. However I don't have time in say, the next two months to do this.