Step 12: Tweak Collision Volumes
| Switch back to the Default view mode, and take a look at the collision shapes. The importer automatically fits spheres and sphyls (fat-lines/capsules) to the bones. It does a good job, but it is not perfect. For example, you can see that the skin extends well beyond the Spine collision volume. You might want to increase the radius of that sphyl.
Select the spine, and bring up the Edit-In-Place dialog, by pressing the button at the bottom of the Geometry list. Change the radius in the dialog to about 0.15. Note that the spinners increment the values by the current Linear Snap value on the toolbar. You might try tweaking a few of the other volumes as well, but leave the head alone for a minute... |
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| Sometimes you may need to make major changes to the collision geometry of a part. To do this, you need to enter the Geometry Editor. Select the 'bip01 neck' part from the part list, right-click it (in the list) and select Edit Geometry. You will now be in the Geometry Editor. In this mode, different collision primitives for a part are displayed in blue.
Select the tiny blue sphere (or click on the 'bip01 neck_1' element in the list to the right). In the properties section, change the radius to 0.1 and move the sphere so that it is aligned with the head. Click on Finish when you're done. Note that there is no undo within the Geometry Editor, but you can always click cancel to undo the whole edit. Alternatively, if you click Finish, then the change is put onto the asset's undo stack. This means you may want to make a complex change in several stages to benefit from undo. |
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| If you now simulate the asset, you will notice strange behaviour and contacts (red lines). This is caused by parts of the asset colliding against each other now that they are different shapes and sizes. To stop these collisions, you can either select groups of parts to disable, and use the context menu, use the disabled collisions grid (on the flyout menu under the Part List), or select Perform Action and use the 'Disable Part Collisions' action. The last is the easiest for what now needs to be
done.
Invoke the action, and select all the checkboxes. This will enable all parts of the asset to collide against each other, apart from those that are touching in the starting pose, and those that are jointed together. Disabling jointed parts is important to allow overlapping collision shapes at joints. Save your work. |
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Step 13: Simulate and Play
| Try simulating the ragdoll. It should behave properly, and be ready for some serious abuse.
There are loads of things you might like to tweak to get the effect you want. Try altering the mass properties of parts (note that to be really correct, you should redo the mass props calculations after changing collision volumes) including damping parameters. In Mass Properties view mode, you can move the centres-of-mass and graphically play with the inertia. Try using different joint parameters, and joint types - although remember that any joint that allows linear movement (such as Prismatics) may stop ragdoll simulation in UT2k3. Play with the simulation options to explore Karma, but again remember that these are dictated by UT and not the .ka file when in game. That's all for now. Enjoy playing with KAT and Karma, and create some cool stuff. Details of how to use your ragdoll in UT2k3 will be posted either here or at udn.epicgames.com soon. |
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