View Full Version : Extrude a flat surface, but end is capping?

Dan Wade
07 July 2002, 10:54 PM the title says.....i am extruding a flat surface in xsi, but i want the extruded face to be filled....but it isn't. Carnt see any option in my extrude panel that allows me to cap.

Dont want to sort this out afterwards, as my surface is made of many segments. I thought

Any ideas? I thought this would be easy?

Cheers in advance,

07 July 2002, 12:59 PM
Extrude a poly with capping.
Select poly.
Right click.

Does this not work on your machine?

08 August 2002, 06:49 PM
:rolleyes: select the polimsh you want to extrude, click ctrl D and translate the new poly in the X, Y or Z.

I hope it helps!!

08 August 2002, 11:12 AM
There's only one way around it that i know of...
If you think about it the side that you're pulling out is capped but the bottom is gone. if this were the side of an object it would be fine because you would already have another side.

the only way i know of to fix this is this:

1) select the polys you want to extrude

2) extract selected polys (freeze them)

3) now extrude from original model

4) merge the two meshes

5) should be a nice solid mesh (YAY!)

6) happy dance!

-EAP! (an avid XSI user!)

02 February 2005, 06:33 AM
OK, I though I'll contribute my 2 cents (if that) to this old capping discussion, since 1. It may help someone, who knows? 2. I'd like to make clearer what the problem actually is, since some of the previous posters seem to have missed it, 3. I think I should slightly refine the approach suggested by EAP! since it may create a small problem for the novice, and 4. someone may finally tell me that I'm an idiot and this can be done in a much more straightforward manner. Frankly I'm a bit surprised that it takes all those steps to achieve this simple thing.

So, what's the deal with capping an extrusion? In many cases, probably 99% of the cases, the simple Ctrl-d-move-component works fine. But consider this: you have a single, isolated square polygon, and you want to turn it into a cube. If you extrude that single polygon you almost get a cube, but not quite: the *bottom* is missing. That's the "capping" some people are asking about, I think.

Of course, if all you need is a cube, there's no need to start extruding squares. But there are cases (I've just been to one) where you have some more complicated flat geometry that is "open", namely it doesn't have an inside and an outside, and you want to "thicken" it to make it 3D, so that your current geometry becomes both the floor and the ceiling of the result. The original mesh is usually relatively flat but it may also be curved, contain holes, etc.; the only thing is that it's like a 2-sided sheet of paper rather than a surface already enveloping some 3D object.

So, here's what I think you need to do. In the following description I'm assuming the original geometry lies more or less flat on the X-Z plane so that "up" and "down" have the usual meaning.

1. Select your existing mesh.

2. Duplicate it by pressing d (not Ctrl-d!), or extracting the polygons as EAP suggests. Make sure the duplicated mesh is located at the exact same position as the original one. This duplicate will be the "floor".

3. Freeze the duplicate. This is particularly important if you extracted polygons; I don't think it's necessary if you used a simple Duplicate command.

4. Invert polygons in the duplicate. This is necessary since otherwise the merge later on will leave some troublesome hard edges. Basically you are making sure that the normals on the duplicate are pointing *outwards* (what will be outwards once we're done with the process).

5. Re-select the original mesh and extrude it as usual: select the polys, ctrl-d, and push upwards. This creates the "ceiling" and the "walls" of the final object; the floor is still there. Of course you may choose to extrude downwards in which case you don't need the inversion in step 4. Look at the normals if you're not sure.

6. Merge the original extruded mesh and the duplicate. That's it!

I hope this helps someone, somehow, and again - if this is not the right way to do this, just let me know.


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