View Full Version : Breaking apart / subdividing polys?

11-27-2007, 08:22 AM
Hello all,

Im working on a model in which I will be exporting it to Zbrush for further detailing. Im using a enlongated Disc primative to create a cylindar for a spray can. The issue is that when I import my model, Zbrush only works with 3 and 4 sided polys (from the error I received) but the end of the cylindar is close to a 48 sided poly. When I created the cylindar, I gave the model about 48 sides but there are only two polys to cap off the top and bottom.

Is there anyway to break apart the top and bottom polys so I can export it correctly. The only method I can think of is the Knife tool, but I dont want to divide the entire model while cutting. Any suggestions?
I suppose I could just recreate my model in ZB but I like LW and its already made.


11-27-2007, 12:18 PM
You can easily subdivide the can. I would just use bandsaw on the sides, then use extender or bevel to create additional geometry on the planar ends. Once you have a loop or two cut in to help support the subdivison there you can use the scale tool on the remaining disc polygon to pinch in the polygons. Then delete the now 0% scale poly and merge the remaining points. This will create a circle of triangular polys that you will want to selectively merge until you have a circle of 4-point traingular polys.

The Cut tool will also help, it cuts polys in the order of selection, allowing you to create some twists and turns in your cut if you need it.

As a side note when freezing sub-Ds, Catmull-Clark sub-Ds can be n-sided polys and always subdivide into quad polys, even from triangles.

Im attaching a pic of how you want the ends divided because my explanation may be a little wordier than it needs to be.



-Oliver Thornton

11-27-2007, 01:00 PM
You can delete the ends and then create 4 splines with 12 points per spline. Patch it 12x12 and it will give you a grid of quads on each end of the cylinder.

11-27-2007, 01:09 PM
You can delete the ends and then create 4 splines with 12 points per spline. Patch it 12x12 and it will give you a grid of quads on each end of the cylinder.

I do so love learning new ways to do things, thanks Larry!

You probably want to use Splinegod's technique, it will give you a very nice even distribution of polys, which is great for ZBrush. It completely avoids the issue of the uneven sizing of polys that pops up using mine, saves time spent merging points and polys, and you can still add cuts if you need to add sharpness to the edge.


11-27-2007, 02:01 PM
Thanks for the quick replies othornton and SplineGod, I appreciate it!

Im not entirely on the same page as you guys, so Im still a bit confused haha. After deleteing the ends, do I go Create>Curves>Spline Draw, or some other tool?

With the picture Ive uploaded, I used the beginning your suggestion, SplineGod, but created a point at the bottom center of the cylindar. Then I selected two points from the rim and the center point and hit the "make polygon" tool (will do the same for the top).

My only real concern with all of these processes is whether they are "water tight" or not. Reason being, after I complete this model I will be sending it in for 3d printing to be made into a real model for a gift. In order for the company to make it, the model has to be completely sealed off, so that is why I am asking. Im sure Im trying to do too much with my current knowledge level in these programs...but its so cool :D


11-27-2007, 02:54 PM
There are a couple of tutorials on making splines, most of them written by Splinegod. You could start at his homepage or do a search for other posts he has made.

There's also Scott Cameron's excellent collection of LW tutorials on the web:

That being said, you want to delete the end polys, then select the points at the end and copy them to a new layer. Use these points in the new layer to create your spline patches using Make Open Curve and the Make Spline Patch tools and paste them back into the base layer. Delete any left-over splines on the scratch layer you used, then return to your base layer and use merge 'm' to close up any holes in your mesh.

should look a bit like this: