True Extrusion Length?

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Old 01 January 2013   #1
True Extrusion Length?

I want to extrude a horizontal slice of a box out 100 centimeters, but using the Local Normals setting so that the polygons stay connected. I notice when you do this, your extrusion doesn’t seem to actually go the designated length. So while I can input 100cm into the spinner, I end up actually getting a distance of 70.711cm away from my starting point.



Anyone know how I can get an actual extrusion of the correct length?
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File Type: jpg extrusion.jpg (79.2 KB, 10 views)
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Old 01 January 2013   #2
did you try the resetXform utility before extruding?
 
Old 01 January 2013   #3
My guess is it is measuring the new edge length. Which in the case of Local Normal is the diagonal edge, and not the extrusion length. To get the actual length you would probably end up needing to calculate a trapezoid height, which becomes a more complicated matter as you need the length of all sides.

Sounds like a good SAT/General Feature request for User Voice.
-Eric
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Old 01 January 2013   #4
In that case you could detach the faces and use the Shell modifier instead. With or without "straighen edges" option.
 
Old 01 January 2013   #5
Plastic, good question but this is a new box. No resetXform is needed.

The plot thickens, refer to the new image. Starting from the bottom up, the 4 operations are:

1. Extrude with Local Normals.

2. Extrude with By Polygon.

3. Faces detached with Shell Modifier, default.

4. Faces detached with Shell Modifier with Straighten Corners enabled.

So apparently detaching faces, then adding a shell modifier with Straighten Corners will work. I think this should be the default behavior of the Extrude operation by default. I guess I will add this to the SAT unless anyone has any other ideas. Also, Straighten Corners should be on by default in the Shell Modifier.
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File Type: jpg extrusion_2.jpg (81.5 KB, 12 views)
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Last edited by Decency : 01 January 2013 at 08:21 PM.
 
Old 01 January 2013   #6
I think straighten corner is set to off by default because with very sharp angles between faces the mesh goes crazy when it's on...
 
Old 01 January 2013   #7
Extruding by local normals is pretty bad actually. As you've seen the distance is the diagonal edge which isn't usually what you want. It's worse if the object is an L shaped box (like maybe a basic building shape) then you end up with distorted extrusions as each edge is extruded by the same amount, but the extruded polys don't end up straight. It's all a big mess IMO.

Shell with straightened corners is MUCH better at dong this.

And yes I agree it is something that could be improved soa feature request is a good idea.
 
Old 01 January 2013   #8
I submitted one this morning. It's weird how this never really occurred to me in the years I've been using Max, and it seems pretty silly to have to use a shell modifier to do this. I've been using AutoCAD and Sketchup recently and after seeing how easy it is to be accurate in these programs, Max feels pretty clumsy by comparison.
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Old 01 January 2013   #9
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