On the XSI mailing list, a poster asked:

If I have a sphere and I want to get the point positions from the sphere and
see what their point positions are in reference to another null’s transforms
how would I do that?

It’s basically a two-step procedure. First convert the point positions from the local coordinate system of the sphere to global coordinates. Then, second, convert the global coordinates into the local coordinate system of the null.

It’s a little more efficient to combine the two matrix combinations, and then apply that to the point positions:

Here’s a video walkthrough of how to build an ICE tree that converts point positions from the local coordinate system (aka reference frame) of one object to the local coordinate system of a second object.
http://vimeo.com/24275969

For ICE beginners. A look at a few different ways to emit particles from the vertices (aka points) of an emitter object.
http://vimeo.com/24214573

Assuming that the PolygonIndex and PolygonPosition sets are in the same order, then given some polygon indices, you could get the corresponding polygon positions by using the indices to index into the PolygonPosition array.
Here, I’m using PolygonInsideNull, which is a set of polygon indices:

Here’s another screenshot that I took to verify that I was getting the right positions.
The purple numbers are the PolygonPosition and PolygonIndex arrays:
Continue reading →

Here’s a simple example of using an array instead of a loop in an ICE tree.
In general, for performance, you’d like to avoid repeats and loops in ICE.
This post is in repsonse to this thread.

var u = 4;
var x = -.05;
for (i=1; i <= u-1; i++) {
	x = x + 1/u ;
	LogMessage( x );
}
// INFO : 0.2
// INFO : 0.45
// INFO : 0.7