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Old 12th September 2007, 03:22 AM   #1
jerrylynnb
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Default Create Convex Surface Object - odd result

I wanted to create the inside of an irregular ditch. I used the polyline feature and drew curved lines from the top of the ditch at one end going down and up to the other side. I moved down the ditch a bit, and drew another line from top, down into the ditch, and back up again. I repeated this several times, making each curve different from all the others so that it would appear not to be dug with a machine, but, by hand and therefore not smooth nor even.

Then I used vertex mode, selected all the vertices from all the lines, and then selected Create Convex Surface Object, but the result was wierd. The bottom part of the ditch was like I wanted, where every vertex from adjacent lines was connected and a bunch of triangles were formed, but on the sides of the ditch, many vertices were ignored, and widely separated vertices were connected bypassing all my hand-created vertices in between. Why did it do this? How can I get it to connect each vertex to the nearest one on an adjacent line?

Also, I didn't want it to close the top, nor the ends - how do I prevent that from happening? I tried to delete the top by deleting the uppermost vertices, but, since it had skipped over most of the vertices on the side, this wound up deleting too much of the sides on of the ditch.

This feature is what I have heard called "lofting" elsewhere, and I was thinking it would figure out more precisely which vertices should be matched up with those closest on adjacent lines - am I missing something?
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Old 12th September 2007, 05:54 AM   #2
Andy
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Default Re: Create Convex Surface Object - odd result

The convex surface/object is just that - Convex. Imagine streaching a large rubber balloon around the vertices and then letting go. Any vertices on the outside of the enclosed shape would be touching the balloon and any vertices that are inside will not. (That's an odd descriotion but I hope it illustrates it 8-) ). This can still be useful for this sort of thing e.g. making ship hulls from profiles etc - you can easily select the 'top' surfaces and delete them.

To make your ditch, I think you probably want to use Vertex->Create-2d-mesh->plan on your vertices.
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Old 12th September 2007, 06:01 AM   #3
Dennis
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Default Re: Create Convex Surface Object - odd result

The "Create Convex Surface/Object" command will ignore surfaces that go "inside" what would be considered a shell of your selected vertices. It doesn't sound like that's the command you want, since you'll have many ins and outs in your ditch.

You could try selecting pieces of the ditch and use the "Create 2D Mesh". you might want to do this for one side, the bottom, then the other side, then merge the meshes together. Depending on how irregular the vertices in the ditch are, however, this could be troublesome.

I came up with an alternate method you might want to consider. It does require a free 3rd party plugin for AC3D called "Noise" that works on Windows or Mac. If you're on a Mac, we can try to get this available to you if you're interested in this alternate method.

The results shown here are with very little care for customization. The contours of the bumps seem to hint more at a path eroded by a waterway, but you can tweak the noise parameters and the main structure of the ditch to get very different results, probably very close to what you're looking for.

The method is explained in the attached images.
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Old 12th September 2007, 06:06 AM   #4
Dennis
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Default Re: Create Convex Surface Object - odd result

Below are the rest of the ditch steps.

Couple more notes:

In the last screenshot above, I ended up making the surface 1-sided and flipped the normals.

Also, this makes a rather high-polygon ditch. If you need lower resolution, the Object -> Reduce command works very well. (You may want to commit subdivisions before performing a Reduce.)

Finally, you can find the Noise plugin at http://supercoldmilk.com/ac3dplug/noise.html

HTH
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Old 12th September 2007, 12:55 PM   #5
jerrylynnb
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Default Re: Create Convex Surface Object - odd result

OK, I get it now - I can wrap a football this way, but not a peanut. Makes sense- "convex". I feel kinda stupid right now for not seeing that myself.

I''lm going to try the other methods - that plugin has a "hair builder" tutorial that definetly sounds interesting.
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