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View Full Version : Basic question on Extrude tool.



DMarkwick
04-11-2011, 05:04 AM
Whenever I use the extrude tool to extrude a poly or a selection of polys, I always find that the resulting new polys are reversed, in that they point in the opposite direction to what I would expect. I have to select the new polys and flip them.

Is there something basic I'm overlooking? I just select poly, use the extrude tool to extrude in the direction of the selected poly, and find that the new polys are all pointing inward.

Tobian
04-11-2011, 05:28 AM
When using the extrude tool, extrude along the opposite of the normal (the dotted line which comes of the face) and the extrusion will work correctly. If you want to go the other way just select the polygon and flip it (f), before the extrude operation. If you've already done it, just select all the affected polygons and flip them all, and their normals will be facing the right way then.

DMarkwick
04-11-2011, 05:31 AM
When using the extrude tool, extrude along the opposite of the normal (the dotted line which comes of the face) and the extrusion will work correctly. If you want to go the other way just select the polygon and flip it (f), before the extrude operation. If you've already done it, just select all the affected polygons and flip them all, and their normals will be facing the right way then.

Thanks for the reply :)

OK, so I need to do a flip either before or after the operation, but it sounds counter-intuitive to me... is it designed behavior? I would imagine that most extrude operations would be done along the normal anyway, why would the tool work along the opposite normal?

Tobian
04-11-2011, 05:54 AM
Well if you think about it, it does make sense, because an extrude operation (in LW, it means different things in different software) is turning a 2D object into a 3D one. Since there already is a 'front', you are adding everything 'behind' that, which is away from the normal facing.

On the contrary to this is 'shift' operations (using multishift, smoothshift or bevel) travel along the normal, because they are designed to extrude out from a surface, by design.

Ryan Roye
04-11-2011, 07:44 AM
Save yourself the headache and use extender plus by pressing "E" and save the hassle of even dealing with inside out polygons in the first place (unless you deliberately do it). I've found it much better for modeling purposes.

Tobian
04-11-2011, 02:17 PM
Hmm, well except extender is no good if you are extruding from the normal, or 'extruding' since it doesn't give a back-face, as extrude does. If you want a 3D extrusion, try the freeware script 'thickener'. Extender is great if you are doing subD work, or certain situations where you need to pull out an edge or face, it just doesn't replace extrude if you want to turn a 2D object into a 3D one.

DMarkwick
04-11-2011, 03:26 PM
So I guess an unwanted side effect of using the extruder tool in the way I described is that it leaves behind an unwanted extra poly... representing the back face of the newly created geometry?

Tobian
04-11-2011, 03:44 PM
No, if you've got an 'unwanted back face' then you wanted to do a 'shift' operation (LW parlance) not use the extrude tool. In which case use smooth shift, bevel, multishift or extend + a translation operation, as mentioned previously.

Extrude is a tool for making a 2d face(s) a solid object. The others are for pulling faces out from a surface, creating a ring of quads behind it.

DMarkwick
04-12-2011, 02:56 AM
I think I understand about the extrude tool now, I've gone from it making no sense to it working perfectly logically, thanks for the explanations :)