**Yang Shen>>
CS5610>> ****Final ****Project**

**Project paper:**** Chris Wyman. ****¡°An
Approximate Image-Space Approach for Interactive Refraction¡±.** **ACM Transactions on Graphics 24(3), 1050-1053.
(August 2005)**

**Introduction****:**** ****Realistic rendering and efficiency are both important
in interactive applications, while with the framerate
constraints, realism is always limited because of its high cost. For
refraction, current interactive techniques are restricted to a single
interface. The author proposed an image-based method to approximate refraction
of two interfaces. This method can suffice for many applications because of its
low cost and plausible refraction.**

**1. ****Index of refraction: 0.66. **

**2. ****Index of refraction: 1.0**

**Procedure****:**

**(1)
****Approximating
the point P2.**

**P2 can be approximated by the
following equation:**

**P2
= P1 + dv*T1**

**Where P1 is the hitpoint, T1 is the transmitted direction, and dv is the distance between backface
and frontface in the direction of T1.**

**dv**** can be approximated directly by the distance between
frontface and backface. To
get the distance, Chris suggested that firstly, get the depth buffer of frontface and backface, then compute
the distance using the two z-buffers. **

*Distance
to **frontface**, distance to backface,
distance from frontface to backface.*

**(2)
****Determine
the normal N2.**

**The idea of determining N2 is
using the normal texture of backface. Once get the position
of the point P2, P2¡¯s corresponding uv coordinate in
the image space of the backface normal texture can be
obtained. Hence, N2 can be obtained from the backface
normal texture.**

*Normal
texture of frontface, normal texture of backface*

**(3)
****Result**