Question: Centroid Function

[cgijedi]

Hi all, I'm trying to get the centoid of a sop using the centroid function. In help, The syntax is as follows:

centroid(SOP, type)

it then goes on to describe the types as eithr D_X, D_Y, D_Z.

does this mean centroid("/obj/geo1/sopName", D_X) would return the X component of the centroid for that SOP?

I don't seem to be getting a result for this or when i subsitute TX, or just X in for D_X.

What am I obviously missing here?

thanks

~cgijedi

[Jason]

Hi there,

D_X is like an enumeration for the index into the position - which is a float[3].

You can use the (lexical) enumerator OR the numeric value it represents:

D_X is 0

D_Y is 1

D_Z is 2

So no other enumerations are defined for the centroid function.

Does that make sense?

Hope it helps,

Jason

[cgijedi]

Yes, that makes total sense. I'll give it a shot.

danke~

-Andrew

[grasshopper]

Another way to go when finding the centroid of a SOP is to append a bounds SOP to calculate a bounding box and then an add SOP which adds a single point set to the centroid using the variables: $CEZ $CEY $CEZ.

You can then reference the centroid from elsewhere with point expressions that reference the centroid. The centroid will be the 9th point in the list of points in the add SOP as the other 8 points are the corners of the bounding box but you need to refer to point 8 rather than 9 as counting starts at 0. That is, point ("/obj/geo/add",8,"P",0) can be used to get the X value, point ("/obj/geo/add",8,"P",1) gets the Y and point ("/obj/geo/add",8,"P",2) gets the Z.

Hope hat makes sense!

john.

[edward]

In case anyone is wondering why would anyone want to do it in such a convoluted manner, I'll defend john. It might be more speed efficient if you have lots of centroid expressions referencing the same geometry because it would then recompute it each time whereas the SOP approach will only do it once.