hiding lines when body parts cross each other

basshole · Post by **basshole** » Sun Mar 16, 2008 11:37 am

Sorry, don't know how to word it better than that.

What I mean is, sometimes when an arm or leg goes through it's arc of movement there's a point in that arc where one of the edges on the leg or arm should disappear, but should not stay invisible all the time. I've been able to solve this to some degree just by drawing the limbs carefully, but sometimes this doesn't work.

My not-very-familiar-with-the-program solution was to create shapes on top of the limb that needs its edges hidden. These are small shapes that are shaped and placed perfectly to hide the edge of a leg or arm at a specific point during its arc of movement, but allow the edge to "reappear" when it looks right.

Here's my project:

http://joshbass.com/Site/Home_Page_file ... 2no3d.anme

Take a look at his left upper arm, for instance (the "L arm" layer). You'll see that in addition to the arm itself, there are two small shapes (I could've gotten by with one, but I thought I needed two, and I just left 'em) that combine to hide the edge of the arm at certain points when you move it.

This works okay, but I'm sure there's a better way. Just curious as to what it is.

slowtiger · Post by **slowtiger** » Sun Mar 16, 2008 11:56 am

Your solution is one I used myself.

Another way goes like this: I draw the line which eventually needs to disappear with some more points than necessary, then switch off one line segment between them. If I arrange the points very closely, nobody notices that. When I reach the moment a line has to disappear, I just move the two points around my line gap.

Not elegant, but it does the trick.

Rasheed · Post by **Rasheed** » Sun Mar 16, 2008 12:00 pm

I would use the

Line Width tool.

It is an animateable tool (keys in the Timeline). To use it, you select a point with the Line Width tool and drag the cursor to the right to make the width larger, and to the left to make it smaller. Sometimes, you will need to add an extra point in your design to have to best possible effect. If you click on a point, it immediately goes to line width zero.

You can remove line width by deleting keys in the Timeline windows, either in the global Line Width channel, or the local Selected Line Width channel (only applies on the points currently selected).

The tool also works on several points at once, but then you need the

Select Points tool. To speed up work, you'd probably use the key shortcuts (W = line width, G = select points).

I hope this helps.

basshole · Post by **basshole** » Sun Mar 16, 2008 8:59 pm

So you guys are actually suggesting to key frame the lines? I was hoping to find a solution where I wouldn't have to do that. I thought maybe there was some kind of way to draw/bind/ the points/lines so they would always disappear at the right place. If not, I'll use the method I came up with.

mkelley · Post by **mkelley** » Sun Mar 16, 2008 9:26 pm

I absolutely key the line width -- it's not nearly as onerous as it sounds. Just scrub through your animation and right before it crosses click the line width to add a key, then move a frame forward and reduce the width to zero and move to where it uncrosses and add another key and then copy the very first key to the end.

It takes all of a few seconds -- and most animations this won't happen often (perhaps once or twice) so at the most you're spending less than a minute to get it right.

I do the same thing for bending arms and legs -- that is, I key the vector point movements to look correct. It sounds like a lot more work than it actually amounts to, and while in theory something automatic would be wonderful it really isn't needed.

basshole · Post by **basshole** » Sun Mar 16, 2008 9:32 pm

Alright, Thanks.

slice11217 · Post by **slice11217** » Tue Mar 18, 2008 8:26 pm

Perhaps this might help you. After playing around with it I found that it gave me a lot to think about when I created my next character model:

viewtopic.php?t=4970&start=0&postdays=0 ... ght=joints

Probably one of the most valuable forum posts I've seen. I wish there was some way to have a 'favorites' link on the forum so that every time you sign in, it would keep the forum posts saved for your reference. I had to dig a little bit to get to this one.

Slice

basshole · Post by **basshole** » Tue Mar 18, 2008 10:49 pm

I remember seeing that before and being impressed, but thinking it looked complicated. I'll give it another look. For now, I think my "shape blobs" method of covering the lines when they need to be covered and revealing them when they don't works pretty well. I do have more characters to design, so perhaps I'll try that on one of them. Thanks.

basshole · Post by **basshole** » Fri Apr 11, 2008 9:07 am

Ok, another solution I've found without keyframing is to create another bone, bind a point on the problematic line to it, and have that bone be controlled by the movement of the limb that's causing the problem. What I mean is, for instance, when a thigh moves to a certain point, the line on the torso where the thigh meets it starts to overlap in an unsightly way. You make a bone, controlled by the thigh's rotation (using bone constraints, I mean), bind the point on the torso's outline that overlaps problematically to this bone, and tweak until the rotating thigh causes that point to move correctly so it never overlaps. I've used this a few times, may not work for all instances of this issue.