plane.py

"""A ray-traceable Plane is a Plane through a given
   point with a given normal and surface material.
   It needs an intersect method that returns the
   point of intersection of a given ray with the
   plane and a normal method that returns the normal
   at a given point (which is irrelevant for a plane
   as the normal is the same everywhere)."""

from geom3 import Vector3, Point3, Ray3, dot, unit
from math import sqrt
from hit import Hit

class Plane(object):
    """A ray-traceable plane"""
    
    def __init__(self, point, normal, material):
        """Create a plane through a given point with given normal
        and surface material"""
        self.point = point
        self.norm = unit(normal)
        self.mat = material

    def intersect(self, ray):
        """Returns a hit, or None if the ray is parallel to the plane"""

	t = None
	hit = None
	angle = ray.dir.dot(self.norm)
	if angle != 0:
	    t = (self.point - ray.start).dot(self.norm)/angle
	    if angle < 0:
	        hit = Hit(self, ray, t, (), self.norm, self.mat)
	    else :
	        hit = Hit(self, ray, None, t, self.norm, self.mat)
	else:
	    vector = unit(ray.start - self.point)
	    if vector.dot(self.norm) < 0:
	    	hit = Hit(self, ray, None, (), self.norm, self.mat)
	    else:
	    	return None
	if self.mat.texture and hit.entry > 0:
	    hit.texCords = self.texCords(ray.pos(t))
	return hit


    def texCords(self, point):
    	vect = point - self.point
	u = vect.dx
	v = vect.dz
	return (u, v)