Merge branch 'master' of forge.bexus.org:Stephan/geometryfactor

geometryfactor.py

@@ -1,7 +1,7 @@
 #! /usr/bin/python3
 
 from sys import argv, stdout, stderr
-from math import pi as π
+from math import pi as π, floor
 from math import atan, atan2
 import numpy
 from numpy import sqrt, sin, cos, tan, array, arange, empty, cross, newaxis
@@ -270,12 +270,23 @@ def box(x=1.0, y=1.0, z=1.0):
         plane(vector(y= y), vector(x=1), vector(z=1)),
     ])
 
-def prism(n=6, a=1.0, z=1.0, φ=0.0):
+def prism(n=6, a=1.0, z=1.0, φ=0.0, n1=0, n2=None):
     p = [
         plane(vector(z=-z), vector(x=1), vector(y=1)),
         plane(vector(z= z), vector(y=1), vector(x=1)),
     ]
-    φ = 2*π * arange(int(n))/n + φ
+    if n2 is None:
+        n2 = n
+    else:
+        c = cos(2*π/n * n1)
+        s = sin(2*π/n * n1)
+        p.append(plane(vector(), vector(c,s), vector(z=-1)))
+        c = cos(2*π/n * n2)
+        s = sin(2*π/n * n2)
+        p.append(plane(vector(), vector(c,s), vector(z= 1)))
+ 
+    φ += 2*π/n * arange(int(floor(n1+0.4999)),
+                        int(floor(n2+1.5001)) )
     p.extend([
         plane(
             vector(a*c, a*s),