Extrude modifier not capping correctly

[Nachi]

Hey folks,

I am creating a facade for a tower using splines, then using the extrude modifier to give the facade thickness and capping. It's a technique i use quiet often, its very comfortable for making adjustments,. The problem is that i am getting a broken up extrude cap (see images attached), it seems max doesn't know how to cap it correctly. does anyone have a good solution for this?? its a problem that reoccurs once in a while for me with this technique. Thx a bunch!!

[Ismael]

http://forums.cgarchitect.com/23986-extrude-closed-spline.html

[Stephen Thomas]

It's a good idea to go into utilities (the hammer icon on your command panel) and run 'shape check' on the spline to detect any problems too before extruding.

[Nachi]

Hey Ismael,

Thx for the reply, but all those options won't work for me. my spline was drawn in 3d's max. the vertices are corner vertices, so no handles exist and they are aligned. when i change the extrude method to grid, it gets a bit better but still, there are flaws, as seen in the attached image.

What could solve this?

[Nachi]

Ive also checked the shape check and it tells me that the shape is okay...

[luthias42]

One of the issues may be that one or more of the indiviual Splines could be causing the problem. I've had to redraw a shape or 2 at times to get the extrude to work right.

 

Another opion that might work is to bump a row of splines one way or another, it will your model slightly off but you should be able to make it close enough to not be noticed

 

the final option I can think of is to divide object in half (top,Bottom) which should also eliminate the problem.

 

the problem is that max can't always handle that many shapes in an object.

hope this helps

[Ismael]

Nachi,

Could you post a simple max file with the troubling splines? I would like to work on this problem, not that I am any kind of expert, I am just curious and sure thet someone will get to the bottom of this.

[TSuess]

Extruding a polyline with this number of openings is going to cause wacky geometry. The polygons are gonna be crazy. Either divide your long line segments several times before you extrude. Or better yet use the shape as a template for your geometry and fill in with boxes and since the geometry repeats copy, copy, copy. It'll be easier to edit in the long run as well.

[Peter M. Gruhn]

It's more work, but:

To create good geometry.

Extrude w/o capping.

Use shift-move to pull out some edges where needed.

Use lots of Bridge.

 

Only do one face.

Delete all the back stuff.

Add a shell modifier.

 

-------------------------------------

 

Make a plane under the spline. (a little below is OK for visibility, just never snap to Z)

Use edge connect.

Move loops with axis snap constraint.

And maybe some cut.

And maybe some move verts with snap axis constraints.

Delete window polys.

Shell.

[cupsster]

draw spline

check spline for continuity

add edit poly/convert to poly modifier

extrude

 

...untested

[Nachi]

Hey Guys,

Thx for all the replies. It seems that there is no perfect solution for this problem.

Ismael, ill post a max file tomorrow when i get into the office.

Meanwhile, (and Thx William..) the best solution i've found is to change the extrude method to grid, and

to tweak a row of splines a bit, which is not noticeable in the grand scale of the model..then everything works out.(strange that this works...???)

The option to polymodel the facade will work, but thats not really comfortable.

There should be a script or plug that fixes this problem...right??

[Ismael]

Thank you Nachi, I look forwards to it.

[TSuess]

Well, I think the point is even if this did work it wouldn't result in "good topology"

 

http://www.cgarchitect.com/news/newsfeed.asp?nid=5035

 

You would end up with these really awkward polygons.

[ATTACH=CONFIG]41865[/ATTACH]

[Nachi]

Hey, first of all, it seems that the uploader won't let me upload a max file.

not sure why that is.. ( sorry Ismael )

Second, about the topology, i dont see why clean topology is important in these kinds of facades if it wont affect the final render. am i wrong?

[David Arbogast]

Sometimes I get issues extruding complex shapes like yours (it's got a lot of holes with filleted corners and max is having trouble figuring out how to triangulate it). In your case there might be an easy work-around. Your facade has a lot of repeating patterns, so rather than trying to extrude the entire wall as a single shape, try to reduce the extruded shape to a smaller section of the wall, extrude it, and then just instance-clone the repeating sections. The advantange to that scenario, is that your extrustion will probably work because it will be simplified and you'll have more parametric control (if the openings change, you can change it in the one section and all the others instances would update).

 

But, if you really prefer doing it as a single extrude, you might try is to help Max out a bit by adding vertices along the perimeter of the facade. Max can use those vertices to better triangulate the extrusion and it will improve the topology of your extrusion. Doing that simply involves selecting the perimeter linework in the segment subobject mode and using the "divide" command (type in a number of divisions that corresponds to the repeating openings).

 

Hope this helps.

Edited March 16, 2011 by David Arbogast

[Ismael]

That's ok Nachi, thank you for trying, but in case some other time you need to upload a small scene, I am sure that we are allowed a zip file even if not a Max file. Other people use a free service, Megaupload or some other like that.

 

Thanks

[TSuess]

divide your long line segments several times before you extrude.

 

But, if you really prefer doing it as a single extrude, you might try is to help Max out a bit by adding vertices along the perimeter of the facade. Max can use those vertices to better triangulate the extrusion and it will improve the topology of your extrusion. Doing that simply involves selecting the perimeter linework in the segment subobject mode and using the "divide" command (type in a number of divisions that corresponds to the repeating openings).

 

This has been suggested twice now and will most likely solve your problem. Have you tried it?

[Peter M. Gruhn]

w/o checking, I'd worry that the root code for the convert to poly is the same as for the extrude modifier and would have the same problem.

[TSuess]

Dividing the line segments works with convert to poly as well.

 

1. Draw a rectangle, convert to poly, look at your poly count.

2. Draw a rectangle, convert to spline. Divide all segments by 3, convert to poly, look at your polygon count.

 

option 1 creates 1 Polygon

option 2 creates 16 Polygons.

 

Works the same with extrusion. David is correct this will fix Nachi's issue.