Hi Elizabeth,
There is probably a better way to do this, but since Orion doesn't have particle support at the moment, I have a routine for drawing the particle at position "r" onto a volume rendered image with arbitrary orientation.
import numpy as na
def add_star_projected(r,ax,cam,ms):
""" Adds the particle at position r to Axes ax. Needs information on the orientation of the image plane contained in cam """
north_vector = cam.unit_vectors[0]
east_vector = cam.unit_vectors[1]
N1 = cam.resolution[0]
N2 = cam.resolution[1]
c = cam.center
r = r - c
W = cam.width[0]
y_pixels = floor(na.dot(r,north_vector) * (N2/W) + N2/2.0)
x_pixels = floor(na.dot(r,east_vector) * (N1/W) + N1/2.0)
ax.hold(True)
ax.plot([x_pixels],[y_pixels],'wo', markersize = ms)
ax.hold(False)
ax.axis((0,N1,0,N2))
Assuming you're using the Camera interface, that contains all the information you need to do the conversion. If you can get a list of particles w/ their positions (we have our own way of doing this that probably doesn't apply), you can then loop through that and add them at the correct position on the off-axis projection.
Andrew M