Paint Blend Weight - Weird...

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Old 01 January 2013   #1
Question Paint Blend Weight - Weird...

Hi,

I started by having only rigid weight for all vertices to their corresponding bones and when I paint blend weight it acts weird.

The example shows what I mean. I simply blended at the lower leg but once I look at the pelvis weight, I can see it is now affecting the knee. The same thing happens for a lot of bones. Is there a way blending will only blend between the closest bones?

 
Old 01 January 2013   #2
Nothing?...
 
Old 01 January 2013   #3
Yeah the skin modifier normalizes weights, which is what you want. The best way to blend is to give the major bones 100% weight from the start, or 1.0 in the ABS dialog. Never give vertexes 0 weight but put all the weight on the main bone then you can blend over to the next bone by unweighting it. What this does is monopolize the weights of the verts in the region you want them.

Having weights on the wrong verts usually happens if you accidentally select verts and then weight them like selecting through a model. To make absolutely sure weight the hips, thigh and calf at 100%. Animate your skeleton into the position you want it to move so you can see the deform and then use the brush to blend. Select a bone and paint over the next region to steal a bit of weight from it, hold alt to reverse the process. I usually have my brush set at about 0.2 max strength.


Painting weights is so much better than the alternative however you will have to tweak a few verts manually.

Cheers
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Old 01 January 2013   #4
Thank you very much for replying!

The way I did it for this character is I started off by giving the pelvis 100% weight on all vertices of the whole character. Then, in vertex mode, I selected the upper leg and gave it the whole leg vertices to it, then I selected the lower leg, etc.

I ended up with a fully rigid skinning. Then I went to the knee (selected the lower leg bone) and did a bit of blending. That's where some vertices started to blend with the pelvis instead of just blending between the lower and upper leg.... That's what's super strange. Same thing happens when I blend at the fingers, but it blends with the clavicle I think...

I think from now on, I'll just paint weight (no blend!) with a low strength like you said. Or just eventually get my hands on "Bones Pro" and never get any problems.
 
Old 01 January 2013   #5
Sounds like you are doing it properly.
It should have nothing to do with the skin modifier but, is this a CS skeleton you are trying to skin on top of.

I ask only because I had some strangeness with a biped myself this week.
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Old 01 January 2013   #6
Sounds like the approach I'd use. Rigidly assign everything to one bone, then manually add a second and weight across those, and so on, blending to smooth it off.

You might find it works better if you do a "remove zero weights" before attempting to blend anything. At the moment it's probably got verts assigned to bones based on the original envelope sizes, which might be massive, but with 0 weights. So it's possible that the lower leg is assigned to the pelvis with 0 strength, then when you blend it might add some to this. Not sure why it would, but it might be.

If you remove all zero weights it shouldn't do that. In theory. I haven't actually done much skinning in the last few years so it could be a bit buggy.

You might also want to adjust the max weights from the default of 20 to something like 4. Then you won't end up with lots of small bone weights which can be confusing. Especially when you end up with some verts weighted to say the clavicle by 0.004 or something. It'll make them swim about and can be hard to catch. If you set the max to 4, It'll only use the four you actually assign. But then I work in games. We need no more than four bones per vertex most of the time any way.
 
Old 01 January 2013   #7
Sorry for my late reply. I was intensively being tested for a job so I didn't have time.

Kanga - Thanks! I'm using a CAT rig, not the biped rig. In my mind, the problem can only be at the skinning level no matter what bones I use.

robinb - Thank you for your time. Your explanation makes a lot of sens. The "remove zero weights" might just be the solution. I'll have to test it out later.

When you say the "max weights" do you mean "Bone Affect Limit"? I'm not sure I understand.

Thanks again!
 
Old 01 January 2013   #8
Yeah Bone Affect Limit (stupid name). It's the max number of bones that can affect a vertex.
 
Old 01 January 2013   #9
In the advanced parameters rollout set Remove Zero Limit to 0.01 and then press the Remove Zero Weights button above it. Then try blending.
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Old 01 January 2013   #10
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