Infinite cone-ray intersections
Similar to the case of the cylinder: substitute q = p+vt into the equation, find the coefficients A, B, C of the quadratic equation, solve for t. DenoteDp = p- pa .
cos2 a (vt + Dp - (va, vt + Dp )va)2 -
sin2 a (va, vt + Dp ) 2 = 0