View Full Version : Subdivision and lathe, is this possible?

11-10-2011, 06:24 PM
I'm trying to make a lathe object, but instead of having a high side count, I'm trying to use subdivision surfaces to make it round. I'm having trouble however getting it to work.

I figured applying weights (and maybe some creative welding/unwelding, and quading the top/bottom?) was the answer, and even though I read that LW9 supposedly added edge weights, I'm wondering if this is really true as I don't seem to be able to control the horizontal edges independently of the vertical edges, or I'm doing it wrong (so I'm thinking they're really just vertex weights via an edge selection?)

Anyway, is there a way to make this thing perfectly (well, indistinguishably) round, as if lathed, while still having a flat disc-shaped top/bottom with a sharp 90deg angle between vertical and horizontal, while keeping a low face count?

I realise I might also be able to use "smoothing" in the surface editor, but I'd rather it actually be round as this could be important for other reasons.

11-10-2011, 06:37 PM
Why not just use the lathe tool? A setting in the numeric panel of like 48 will give you a fairly smooth object.

11-10-2011, 06:49 PM
You are needed at http://forums.newtek.com/showthread.php?p=1194017 :D

You must use Catmull Clark for weighting edges; Subpatch weights points. So with Subpatch you will be snapping the points.
With CC weight (Map>Set Sharpness) wou will be snapping the point, but not in all 3 coordinates, so it can go curve.

Bottom line, if you apply Edge Weight like in the image you will get what you are requesting I think.

OpenGL shading can deceive, so you better freeze to check if that is the way you like it.


11-10-2011, 07:57 PM
You are needed at http://forums.newtek.com/showthread.php?p=1194017 :D

Thanks, I'll have a look there, later; I'm going to be a bit busy for the next little while :). I tried to find docs on these edge weights, but they seem to not be documented beyond having been added in lw9.

Why not just use the lathe tool? A setting in the numeric panel of like 48 will give you a fairly smooth object.

I realize I could do that, but I'm trying to keep the poly count down, assuming adding all these weights doesn't offset the savings. (And I'm also trying to learn how to properly use Sub-Ds in more complex cases).

I've had cases in the past where I've just resorted to cranking up the repeat count to get "round", but it seems so brute-force. I want to learn how to optimize (and when I can't).

11-11-2011, 03:26 AM
The other option is to simply add an extra edge very close to the edge you want to sharpen. ie. As per image - sure, it'll increase poly count, but not that much... :thumbsup:

11-13-2011, 03:16 AM
Ok, I got this work (thanks for the pointers). Now If I can just figure out how to interpret the display of the weight-shading.

In this case, horizontal outer edges are edge-sharp 1.0, all other edges (including horizontal point-towards-the-object-axis edges, of which there are some besides the endcaps) are edge sharp 0.0. This towards-the-axis bit is necessary to make the sharp edges curvy.

Side question: What is the difference between "pixar" SubDs and CC SubDs with edge weights?

P.S. lathe made a bunch of extra points and polygons and some flipped normals (I got rid of them here with MergePoint and UnifyPoly), which I haven't decided if that is an error yet or not (did it make an inside as well as an outside?) I assume this accounts for the particularly strange looking subdivision in my picture at the beginning of the thread.