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Postby Azy » Wed Jan 10, 2018 7:47 pm

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  Azy
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Subject title: Form Intersections Critique

Hey all, I'm pretty sure quite a few of these are wrong but I can't quite work them out in my head. I specifically had a lot of trouble with sphere and cylinder intersections. If someone could point out the correct intersections that would be great!
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Postby Bugpal Hopeday » Thu Jan 11, 2018 1:06 am

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These are tricky. The main thing that stood out to me was that if the sphere is a pacman, his bottom jaw wasn't receding enough and was acting cube-y.

Image

I think that is easy to correct if you think of the sphere more in terms of cross sections. I think of it as being like the way they show brain MRI scans on the news sometimes, showing the slices of the brain one at a time.
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Postby Bugpal Hopeday » Thu Jan 11, 2018 2:04 am

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I've just opened up Blender to double check my answer... for science. At this point I'm just following my own curiosity but I'll post it in case it's at all useful.

Image

So it really is like a pacman chugging a beer. The hard part is obviously not the flat part of the cylinder 'cause that acts the same as a cube. It's the curved part.

The intersection of two curved surfaces at these angles often seems to increase the curviness. What I mean is that if pacman were sucking a cube from these angles, the bottom jaw of the pacman would be a bit closer to a ) than a ⊃.

But from the lower angles it's a different story.

Image

Then you get this double curve or S shaped curve. Could also be called the underboob curve. I think the process to follow for this curve it to think about the lines that would go around the curve and the cylinder, and then try to have them converge on a line in the middle. Like this:

Image
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Postby Azy » Thu Jan 11, 2018 6:39 am

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Thanks a ton for going through all this effort for my post! Yeah, thinking of a sphere in terms of cross sections like it could be sliced into sections with a knife is a much better way of thinking than what I was doing, also the pacman analogy is great. Thanks for showing me a better method for going about these intersections.

 

Postby Bugpal Hopeday » Fri Jan 12, 2018 1:11 am

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No worries, glad it was useful. :D
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