Thanks Alok! That works and gives me a nice rig for controlling the distance manually along Z, but I actually need to move the controller around the frame and have it "snap" to geometry, or at least give me a vector I can use to test for an intersection.

On 9/26/2013 4:49 PM, Alok Gandhi wrote:
1 create an ice tree  on a null(call the rig) >
2 get scalar to 3d vector node (you will only change z through a slider, x, y, should be 0)>
3 get a srt to matrix node >
4 plug the scalar to 3d into position of srt to matrix>
5 get a 4x4 matrix node>
6 connect the srt to matrix out to value of 4x4 matrix>
7 get data node camera.kine.global>
8 get a multiply node and connect 4x4 matrix into first port, camera.kine.global into second(order matters)>
9 get a set data node>
10 connect the multiply node's out into value of set data and give it a name like 'xfo' or something>

11. On the controller to snap, create another ice tree. Get data rig.'xfo' and set data to self.kine.global.

you are done. Just move the camera and the controller will follow. To move it on the camera ray path just use the slider created in the step 2.

Wrote this right of the top of my head, did not try it in ice actually. But should work.

Just get the distance between the controller and the camera through an expression or through ice. I suggest expression because getting vector lengths is expensive in ice (that is also the reason we have squared distance node in case it is just a comparison of distances).

Cheers!

Alok.


On Thu, Sep 26, 2013 at 5:15 PM, Tim Crowson <tim.crow...@magneticdreams.com <mailto:tim.crow...@magneticdreams.com>> wrote:

    But the distance I want is the distance between the camera and the
    closest point on an arbitrary geometric surface behind the target.
    Now maybe the easiest thing to do would be to snap the target to
    said surface and get that distance. But there again, I need to
    identify the position in space where the ray from the camera
    intersects that surface.

    -Tim


    On 9/26/2013 4:09 PM, Christian Freisleder wrote:
    Hey Tim,
    I would use a expression.
    open the exression editor-->Function-->Distance-->distance to camera
    the result would be something like
    ctr_dist_cam( null. )
    null. would be the object name you're using to mesure the distance.
    hope that helps
    christian

    On 26.09.2013 22 <tel:26.09.2013%2022>:58, Tim Crowson wrote:
    I'm trying to set up a camera rig that will let me use an item
    of some kind (null, curve...) to act as a kind of focal point
    that can be moved around the frame. Basically I want to have a
    control parented to the camera which I can move around the
    frame, and which can be used to create a vector between the
    camera and whatever surface is "behind" that focal control. I'd
    then get the distance between the camera and that point on the
    surface and pass that to my lens shader.

    I'm really a noob when it comes to ICE in general, so I'm
    wondering how best to do this. I suck with vectors...
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