Plausible Blinn-Phong Reflection
of Standard Cube MIP-Maps

Technical Report

Morgan McGuire, Williams College
Daniel Evangelakos, Williams College
James Wilcox, NVIDIA and University of Washington
Sam Donow, Williams College
Michael Mara, NVIDIA

Abstract
BibTex
Paper (PDF)
G3D Library (contains full OpenGL GUI implementation)

Abstract

We describe the technique used in the G3D Innovation Engine 9.00 to produce reasonable real-time environment lighting. It adds two lines of code to a pixel shader to reasonably approximate Lambertian and Blinn-Phong glossy reflection of a standard cube map environment with a MIP-chain without preprocessing. That is, we combine Blinn's BSDF with Blinn's environment mapping in a modern physically-based way. This technique has the advantage of operating without preprocessing on standard assets and dynamically-rendered light probes. A limitation is that it produces overly boxy blurring for highly varying environment maps with very broad glossy exponents. This technique has been widely explored before. Our contribution is a principled derivation of the constants needed to best approximate with a single texture sample per BSDF term, giving an efficient result in which glossy reflections of the environment and light sources have comparable highlights and intensity.

BibTex


@techreport{mcguire2013cubemap,
 author = {Morgan McGuire and Daniel Evangelakos and James Wilcox and Sam Donow and Michael Mara},
 title = {Plausible {B}linn-{P}hong Reflection of Standard Cube {MIP}-Maps},
 number = {CSTR201301},
 insititution = {Williams College Department of Computer Science},
 pages = {8},
 address = {47 Lab Campus Drive, Williamstown, MA 01267, USA},
 month = {September},
 day={9},
 year = {2013},
 }