On Aug 10, 2007, at 4:04 PM, Elaine Meng wrote:

To manually position a structure relative to another, you could

interactively rotate/translate and/or use the "move" (translation) and

"turn" (rotation) commands. You can freeze/unfreeze a copy using the

Active checkbox in the Model Panel (in the Favorites menu by default),

the command "select," or the little checkboxes under the Command Line

(also under Favorites).

If you did manage to position copy 2 relative to copy 1 to your liking,

you could write the transformation matrices out (see "matrixget"

command). From those you could calculate the transformation of 2

relative to 1 and also generate appropriate matrices that would then

position 3, 4, ... correctly (see "matrixset" command). I admit I

don't know how to do those calculations. Anyone?

It's a little tricky. Basically, you want to get copy 1's matrix to be the identity matrix while keeping copy 2 in the same relative position. Here's one way to do it (and maybe someone can suggest something better):

1) open yet another copy (copy 3) as a reference

2) use "matrixset" to set copy 3's matrix to be the identity matrix

3) use the "match" command with the 'active' keyword to match copy 1 onto the reference (copy 3) while also moving copy 2 appropriately

I would imagine that copy 2's matrix is essentially all translation components (i.e. the upper 3x3 is all zeroes or near-zeroes) so all you need to do to place additional copies to multiply the translation components by 2, 3, etc.

--Eric

Eric Pettersen

UCSF Computer Graphics Lab

pett@cgl.ucsf.edu

http://www.cgl.ucsf.edu