Step 10: Hinge Joints
| Elbows and knees are not modelled well with Skeletal joints, and so we will use a Hinge for each of them instead. A hinge joint constrains position absolutely and rotation except around a single axis. The axis of rotation is the X axis of the joint. Optionally, the joint can be limited, which means that its range of motion is restricted. You need to make all the elbow and knee joints into limited hinges.
To do this, select the joints (calf and forearm, both left and right), and bring up the Joint Properties dialog. Change the Type dropdown to Hinge, and check the Limit Active checkbox. |
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| Unlike the skeletal joints, the orientation of the joint itself is very important with the hinge. You must rotate the joint so that the X axis is the axis about which you want rotation. Normally you will find that using 'Q' and 'Ctrl-Q' repeatedly will give you the orientation you require. Alternatively, set angular snap to 90 degrees and rotate with Alt-Middle- or Alt-Left-Drag as normal.
The hinge limits are a little confusing also. The 'y' axis represents the initial position of the child, and is free to move in the arc described by the blue sector. To start in a valid position, therefore, the y axis should always be between the upper and lower limits. Note also that rotating the joint around the axis of rotation (x) will have no effect. The image to the right shows a correct elbow joint, allowing a small amount of backward motion (the arm is not perfectly straight in the default pose), and a lot of forward rotation. Remember that you can copy joint parameters by selecting the source and right-clicking the destination, but note that this does not rotate the destination joint. Set up the elbows and knees to reasonable values. Remember that you can tab back to the File tab, and double-click the Male asset in the workspace to see a finished skeleton if you are getting confused. |
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Step 11: Change the connectivity
| If you now simulate the asset without pinning it to the world, you will see that it is nearly correct, but that the Pelvis sometimes wobbles about a bit. The solution to this is to connect up the parts in a way more like a real human body. Because of the bone structure of the graphic, the Thighs are connected to the Spine rather than the Pelvis to form hips.
Select both Thigh joints, and display the Joint Properties dialog. Change the Parent Part from 'bip01 spine' to 'bip01 pelvis'. Note that this may reset the limits to the default cones, and you will have to set the limits again. This shouldn't take more than a few seconds though, and when you simulate, you will notice that the pelvis is no longer free to move. The joints should now be correct, and you are getting close to having a finished ragdoll. |
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