[Gate-users] trpd geometry

[Stephen Adler]

http://wiki.opengatecollaboration.org/index.php/Users_Guide_V7.1:Defining_a_geometry 


In the above wiki page, if you scroll down to "Commands of the sub-tree 
geometry for different shapes" table, you'll find the parameters 
involved with defining a trpd object.

I've been working with trying to define such an object in a small 
simulation and have had trouble making it work.

First of all, it looks to me that the "setX1Length: Set half length 
along X of the plane at -dz position" should actually read "setX1Length: 
Set length along X of the plane at -dz position". I'm not sure where the 
"half" bit is coming from but from my detailed debugging of my geometry, 
the number I enter for setX1Length is actually the full length not the 
half length.

Furthermore, I'm having trouble with setting the Z length of the trpd 
object. If I set it too long, then the trapezoidal shape turns into 
something which looks like a broken crystal. Or a trapezoid with someone 
taking a hammer a banging out a chunk in a corner. Are there limits to 
what the Z length should be relative to the X1, X2, Y1, Y2 lengths?

Finally, I'm having a hard time generating a ring of trpd objects since 
I would like the to form a ring of objects with each one touching the 
side of the other. Because of the definition of the trpd object, I have 
to do an initial rotation of the object to align it properly so the 
short face of the trpd object "faces" the Z axis or center of the field 
of view. Then when I apply the ring duplication, my trpd object gets 
rotated out of the XY plane because I applied that original rotation to 
the first trpd object. This could be avoided if there was a Z1 and Z2 
lengths I would set, but it looks like the trpd object assumes the Z 
length to be the same, or the "thickness" to be aligned along the Z 
axis. (If that makes any sense.)

Anyhow... any reply is greatly appreciated.

Cheers. Steve.