Maya for 3D Printing - Rapid Prototyping
In this course we're going to look at something a little different, creating technically accurate 3D printed parts.
# 1 08-09-2013 , 03:59 PM
boybokeh's Avatar
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Join Date: Sep 2013
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Weird question re discrete scaling

I've been using the scale tool with discrete scaling along edge loops to align the vertices along the same axis. Initially I was just using this to straighten out my geometry, but I also realised that by doing this and aligning the scale axis to a relevant face (or whatever custom axis orientation) I can align different edges to one another. I know, I know, pretty basic, but I've only been modeling for a couple of days, so this was quite handy for me to discover.

My actual question is: why does discrete scaling have this effect? I was googling how to straighten out / align my vertices which is how I came across the initial solution, but I wouldn't have figured it out myself. I can say that pretty safely because now that I know what to do, I still don't understand why it's happening.

Specifically, I don't understand why vertices will lock at the same point if you scale discretely along a given axis instead of just continuing to be scaled onwards in steps, which is what I would have guessed would happen. Is the step size important to what I'm doing? I wouldn't have assumed it was, and changing it doesn't seem to make any significant differences the behaviour.

If someone can explain in layman's terms to me what is happening I would hugely appreciate it. If this was an align tool that was specifically intended to do this exact thing then I wouldn't question it, but because it's interesting behaviour in the scale tool I'm trying to find out a bit more.

# 2 16-09-2013 , 02:05 PM
LauriePriest's Avatar
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Join Date: May 2003
Location: London
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Looks as though this is actually a bug ... kind of.
The best way to think of scaling is multiplication, scaling can be defined as:
New Position = CurrentPos - pivot * scale amount + pivot.

All I mean to point out in this is that scaling is just multiplication. So by default the scaling tool lets you go to negative scaling values so you can effectively invert the model, this is a good thing! For some reason (weird), when descreete scaling is turned on it clamps the lower range you can scale by to 0 which means you effectively line up your result.
Hope thats useful for you.


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