# Perp maker

Download the script from this page, sans line-numbers.

```
#
# $Id$
#
#
# perp_maker.py: Nothing to do with cops. Given a simple PyMol scene, attempts to
# create a CGO background triangle perpendicular to the vector created - which is
# parallel to the line segment drawn through the camera point and current center of
# mass - as obtained by "get_position," or "get_view."
#
#
# To use: Load your scene. Orient the scene as you wish. Run the script.
# Could it be any simpler?!
#
# The TTT Matrix has to be the identity, do achieve this result. So,
# run the following:
# -- 'reset'
# -- then orient your molecule as desired using the EDITING features!
# -- before running this script, make sure 'get_view' shows the identity
# -- matrix for the first 9 elements.
# -- then run the script
#
import pymol
import math
import sys
import random
from pymol.cgo import *
from pymol.vfont import plain
############################################################
#
# Methods
#
############################################################
#
# Given the viewVector and center, creates a random sized plane
# perpendicular to the viewVector through the origin. It is then
# the next step's responsibility to move the plane back some so
# it dosen't cut the molecule/scene in half.
#
def getPPlane( viewVector, center, side_length=100 ):
"""Returns a 3-tuple of 3D points representing the perp. plane."""
# for reproduceable testing
#random.seed(10)
#
# The formula for a plane with our chacteristics is defined by
#
# A(x - x') + B(y - y') + C(y - y') + D = 0, where
# A, B and C are not all zero coefficients in the vector
# Ai + Bj + Ck such that the plane is perpendicular to this
# vector; x, y, and z are points on the plane; x', y', and z'
# are the coordiates through which the plane shall run.
#
# This is fool-ass. Gotta' be a better way to do this.
# Declaring that rVal is a 3-Tuple.
rVal = [ [], [], [], [], [], [] ]
# Compose two triangles into a square.
# Never learned any GFX coding, so I'm sure there's something
# better than this; but, this works.
for i in range(0, 6):
if ( i == 0 ) or ( i == 5 ):
x = -side_length + center[0]
y = -side_length + center[1]
elif (i == 1):
x = -side_length + center[0]
y = side_length + center[1]
elif ( i == 2 ) or ( i == 3 ):
x = side_length + center[0]
y = side_length + center[1]
elif ( i == 4):
x = side_length + center[0]
y = -side_length + center[1]
if ( viewVector[2] != 0 ):
z = -(((viewVector[0]*(x - center[0])) - (viewVector[1]*(y - center[1]))) /
viewVector[2]) + center[2]
else:
print "Z-component of viewVector is zero. Now, I need a nonzero value here
so I'm just making one up. :)"
z = random.randint(-200, 200)
rVal[i] = [x, y, z]
return rVal
############################################################
#
# End methods
#
############################################################
#
# First, get the center and camera locations
#
view = cmd.get_view()
camera = [ view[9], view[10], view[11] ]
center = [ view[12], view[13], view[14] ]
#
# Sanity check
#
print "Camera is: " + str(camera)
print "Center is: " + str(center)
#
# Create the vector through the two points directed
# from the camera to the center - the viewVector
#
viewVector = [ center[0] - camera[0],
center[1] - camera[1],
center[2] - camera[2] ]
print "ViewVector is: " + str(viewVector)
#
# Create the plane perpendicular to the viewVector
# running through the origin
#
pPlane = getPPlane( viewVector, center, side_length=100 )
print "Plane points calculated as: " + str(pPlane)
#
# Now translate the plane down away from the camera along the viewVector axis
#
# now create the CGO and load from the points
obj = [
BEGIN, TRIANGLES,
COLOR, 0.2, 0.4, 1,
VERTEX, pPlane[0][0], pPlane[0][1], pPlane[0][2],
VERTEX, pPlane[1][0], pPlane[1][1], pPlane[1][2],
VERTEX, pPlane[2][0], pPlane[2][1], pPlane[2][2],
VERTEX, pPlane[3][0], pPlane[3][1], pPlane[3][2],
VERTEX, pPlane[4][0], pPlane[4][1], pPlane[4][2],
VERTEX, pPlane[5][0], pPlane[5][1], pPlane[5][2],
END
]
cmd.load_cgo( obj, 'pPlane')
cmd.set_view( view )
```