Could any one help me to solve some fundamental issues in rendering shafts of light. I am following the paper "Interactive rendering method for displaying shafts of light" by Dobashi, Nishita and Yamamoto for rendering light shafts. Since I am new to graphics programming, i am finding difficulties in calculating the total intensity of the scattered light Is (Second term of the equation) I struck with the following problems How to construct the virtual plane How can I find the direction towards the intersection point of the ray with the virtual plane? How to store the intensity distribution of light sources as light maps Implementation of projective texture mapping techniques