Skin binding and weight painting
Video: Skin binding and weight paintingSo we've got all our controls set up on our skeleton and we're at a point now where we need to bind the skeleton to the character's geometry. And that's going to allow the position of the skeleton to determine the position of the geometry. So we'll do this using a process called smooth bind. And smooth bind lets each bone in the skeleton affect vertices in the character's geometry. So let's get this set up in the Outliner here. I'm just going to select my skeleton and Shift+Select my geometry.
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Get a thorough overview of techniques for creating characters for video games or real-time rendered applications. Author Chris Reilly covers low-poly modeling, texturing and animation, using 3D model and texture assets created in Maya and Adobe Photoshop. The course also includes an overview of Unity 3, including importing characters and making interactive animations with the Script Editor.
- Optimizing, extruding, and sculpting geometry
- Modeling a character's head and body
- UV-mapping the head and body
- Mirroring and texturing
- Setting up the skeleton
- Rigging the head and body
- Skin binding & weight painting
- Controlling animation with scripts in Unity
Skin binding and weight painting
So we've got all our controls set up on our skeleton and we're at a point now where we need to bind the skeleton to the character's geometry. And that's going to allow the position of the skeleton to determine the position of the geometry. So we'll do this using a process called smooth bind. And smooth bind lets each bone in the skeleton affect vertices in the character's geometry. So let's get this set up in the Outliner here. I'm just going to select my skeleton and Shift+Select my geometry.
Then under the Skin menu, I'll go to Bind Skin > Smooth Bind, with options. So I want to bind to the Joint hierarchy and I want to set this Max influences to 3. So what that means is for any vertex in the character's geometry, only three of the bones will be able to control it. And that's just going to help to simplify our process as we go through and determine which bones affect which parts of the geometry. So I'll go ahead and click Bind Skin. And now if I go ahead and move my skeleton around, I should see that the geometry is moving along with it.
So let me select this left foot control and let's go ahead and turn off X-Ray Shading. So I'll click Shading and uncheck X-Ray. So now, as I bring this foot control up, I can see that the character's geometry is moving along with the skeleton. I can also see it's moving in kind of a weird way. So you see as I move the foot up, parts of this wing and the lower abdomen are moving along with it. So we need to go through and kind of do some fine-tuning to tell Maya which bones affect which parts of the geometry. So I'm just going to undo that movement there. So to edit the way that the skeleton influences the geometry, I'm going to use the Paint Skin Weights tool.
So I'll select my character's geometry. I'm going to go up to Skin > Edit Smooth Skin > Paint Skin Weights Tool, with options. So if you notice when I brought up the Paint Skin Weights tool, my shading changed on my character. So the Paint Skin Weights tool is going to give me a visual indication of the influence for each joint to the character's geometry. So let's just expand this a little bit here. So in my tool settings for the Paint Skin Weights tool, I'll see the entire hierarchy of my character's skeleton.
So this is another reason why the naming conventions are so important. So I know exactly which bones I'm dealing with here and that's just going to make it so much easier as I go through and adjust the weights. So right now, I've got the root bone selected. Let's go down. I want to look at the left knee. And I'll zoom in a here a little bit on the left knee. So the visual that I'm getting with the Paint Skin Weights tool is the wider the geometry is the more influence the current bone has over that geometry. So I can see this part right here, the knee joint has a lot of influence over this geometry.
And then I can see up here on this kind of wingtip is a little bit gray. So that would make sense because as we were lifting that leg up and down, that wingtip is kind of moving around. So there's a little bit of influence from the left knee joint to this wingtip. So we want to go ahead and get rid of that. In my Paint Skin Weights tool settings, I want the Mode set on Paint. I want the Value set on 0. So for each joint in the skeleton, I'll have the option of a weight from 0 to 1.
Now right now, I want to get rid of all of the weighting from that left knee that's applied right now to this bottom of the wing. So I'm just going to set this value to 0, so essentially I'm erasing the influence from that left knee to this area of the geometry. And right now my Brush Size is very small, so I'm going to increase this a little bit. I'm just going to hold down the B key and click with my left mouse button and drag and just increase that Brush Size a little bit. And I'll just go ahead and click and I'm just kind of paint over that area of the wingtip.
You can see as I do that, the color changes from gray to black. So that's a visual indication that I'm removing the influence from that left knee joint on this part of the geometry. And I can see there's even some on the back here too, so I'll just spend a little time painting over this geometry. Let's take a look and see how that worked. So now, as I select that left foot control again and use my Move tool to move it up and down, I should get less distortion.
There's still a little bit, and I think that's probably coming from some on the hip joint and some on the ankle joint, so I need to go through each individual joint and make sure that it's influencing the geometry in the correct way. And that's going to take a little bit of time, but it's not too bad. This is another point in our process where we can take advantage of symmetry. So really all we need to take care of painting skin weights for one side of model and later on I can mirror those over. And I can do that using Skin > Edit Smooth Skin > Mirror Skin Weights.
I want to actually do this right now but I'll just go over the options, so I'll bring up the options for this. And just like when we mirrored the skeleton, I want to mirror over the Y-Z plane, and I do want Positive to negative. So I'm just going to continue like I've been through this whole process, working in the positive X direction and we'll mirror that into negative X. So as I go through the process, I can mirror as I go or I can mirror at the very end. But the point is I really only have to focus on one part of the model until I get all my weights painted correctly. So I'm going to spend some time finishing out the weight painting on the rest of this geometry.
In the next video, we'll look at animating.
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