21 March 2011

Robot Dog (WIP) #6 - Iris Expanded

After the reels went up I was asked how I did the iris on the Robot Dog. I pointed them to wip #5 but i realised i'd actually done more on it since then so ill go over it again.

 First up this is one of the pieces of the iris from inside the shutter. Theres six of em in total and they're all a separate piece of geometry.
 Inside they're all lined up like this. But as i said before they're not flat. Each one is rotated pointy end up just a tad so when it closes, they all sit on top of each other nicely
 Each bit of the iris is parented to 1 of 6 bones, which are also tilted the same amount. Then each is given a copy rotation of the bone in the middle.

nice little tip. i had the pieces flat and the bones straight. did the parenting, then grabbed all the heads of the bones and scaled them out from each other. Giving them all the same tilt and taking the geometry with them.

This is where it starts to get a little fiddly
The range of rotation i want each of the outside bones is between -8 and 34. This'll be different for every shutter, but on this one its the range to open as much as it can before poking out the side and in to be completely closed. Having the limit on this bone means you dont need it on each of the outside bones.
It then has a Transform modifier copying the animating bone Scale and applying it to the rotation.

I have the scale range at 1.3 to .3 because the default pose of the iris isnt completely open and i dont want to have to scale the bone all the way to zero to close the iris.
If all this is done right then scaling the animatable bone should rotate the middle bone which in turn should rotate each of the outside bones bringing the geometry with them.
Iris control through 1 animation bone.

Those 2 other bones you can see are for the position and rotation of the rest of the eye and have no effect on the iris. So just forget about em for now, they weren't invited to the party ;)

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