You may hate me for this, but I need to point out something that might be incorrect in the video, when you do the sphere-cylinder intersection at 17:22. This is a side view of the cylinder and sphere intersection. When you only follow the curvature of the cylinder, wouldn't that be the red line in the side view? If it's just something with flat surface, like a box or pyramid, it's definitely just the curvature of the cylinder; but when it's 2 curved surfaces interacting with each other, I think it has to follow the curvatures of both. To draw that accurately would require one to channel some Scott Robertson, but that became more like technical drawing than dynamic sketching. Fortunately, I found a simpler way to estimate it:
It actually looks like a diagonal slice of the cylinder, which curved into the curvature of the sphere, rather than a sharp turn like how you did in the video.
If the sphere wraps around the cylinder, it will look like a diagonal slice of the cylinder, without the transition to the sphere's curvature:
Aha, good catch! Yes, you're definitely correct. Intersections definitely are not my strongest suit. I'll make an annotation on the video that links to your comment.
But you'd best be lookin' over your shoulder from now on, having called me out in public. I'll strike when you least expect it!
Can you also add a note telling people to just google things like "cube intersect sphere" or "cylinder intersect sphere"? Having the 3d models to observe may help a bit in understanding.
[deleted]
2015-03-26 17:32
Thanks that was helpful. I can do much more complicated intersections when I think about it this way.
Grieffon
2015-04-01 02:01
You may hate me for this, but I need to point out something that might be incorrect in the video, when you do the sphere-cylinder intersection at 17:22. This is a side view of the cylinder and sphere intersection. When you only follow the curvature of the cylinder, wouldn't that be the red line in the side view? If it's just something with flat surface, like a box or pyramid, it's definitely just the curvature of the cylinder; but when it's 2 curved surfaces interacting with each other, I think it has to follow the curvatures of both. To draw that accurately would require one to channel some Scott Robertson, but that became more like technical drawing than dynamic sketching. Fortunately, I found a simpler way to estimate it:
http://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Is-spherecyl5.png/200px-Is-spherecyl5.png
It actually looks like a diagonal slice of the cylinder, which curved into the curvature of the sphere, rather than a sharp turn like how you did in the video.
If the sphere wraps around the cylinder, it will look like a diagonal slice of the cylinder, without the transition to the sphere's curvature:
http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Is-spherecyl4.png/200px-Is-spherecyl4.png
If I'm wrong, I apologize, but please have a look.
Uncomfortable
2015-04-01 02:09
Aha, good catch! Yes, you're definitely correct. Intersections definitely are not my strongest suit. I'll make an annotation on the video that links to your comment.
But you'd best be lookin' over your shoulder from now on, having called me out in public. I'll strike when you least expect it!
Grieffon
2015-04-01 02:20
:|
Can you also add a note telling people to just google things like "cube intersect sphere" or "cylinder intersect sphere"? Having the 3d models to observe may help a bit in understanding.
Uncomfortable
2015-04-01 02:22
Sure.