Here is how I made my iris shutter. It’s a little tedious but it allowed me to use different materials on the blades. Nozzy’s dupliverts would be much simpler, so by all means use dupliverts if they suit you. Procedure details are added for newer users.
In top view, make a mesh circle the size of the fully open hole / portal, with as many sides as you want blades. This will be the guide for accurate placement of the blades, as well as the parent object for all the blades.
Model the blade shape shown in Figure 1 (I took apart an old camera to find the correct shape). Its total length should be about twice the length of one side of the guide circle. Move the blade’s Object center to the indicated position (select blade in object mode, LMB to put the 3d cursor in the desired location, F9->Centre Cursor). In front view, add a slight rotation as shown, to prevent the blades crossing each other when the iris closes.
Now to add the bone that you will use to control iris open/close. This driven IPO is not absolutely necessary, but I think it makes subsequent animation simpler.
Go back to Top view. Add a one-bone armature in the center of the circle
Select the blade. Open an IPO window and do all the following steps while pointing at the IPO window.
Click dRotZ. Press the N key and Add Driver.
Fill in the fields like this.
Driver type: Pose
Loc X: change to Rot Z.
Press I-key and select one-to-one.
Now if you rotate the bone in pose mode (R-Z), the blade should rotate.
4. Snap the blade to a vertex of the circle. Using R-Z, rotate it so the middle of the inside arc just touches the circle (Figure 2). Parent the blade to the circle.
- Now the most tedious step: duplicating the blade around the circle. This will make instances of the original blade that will inherit the IPO driver, and will be easier to edit as a group. Select the blade and use Alt-D to duplicate it. Snap the new blade to the next vertex of the guide circle and rotate it so it touches the circle. Repeat this Alt-D / Snap process until every vertex of the circle has a blade.
When you rotate the driver bone in Pose mode (R-Z), the iris should open and close.
If the shape of the blades is off, you can edit any one of the duplicates and they will all change.
The movement may also end up off-center when you close the iris; here’s a way to correct it. Go to Top view to look at the gate face-on. Rotate the driver bone (in Pose mode) to close the iris about halfway. Select the guide circle and Shift-S, snap Cursor to selection. Add another mesh circle and scale it to fit just inside the current opening. One by one select each blade and rotate it so it just touches the circle. Delete this circle when you’re done.