Program3 - CSci 5108: Programming Assignment #3*...

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* due: 9pm, Tuesday, March 23 Rendering requires the computation of many different types of integrals. In this assignment you will take a close look at how pbrt computes the radiance reflected from a surface in a certain direction by integrating the surface's reflection function (BRDF) against incoming light from all directions. Because these sorts of integrals generally don't have analytic solutions, pbrt numerically estimates their value by Monte Carlo integration. As you are now well aware, the variance of a Monte Carlo estimator manifests itself as noise in a rendered image. It is therefore very important to the quality of your rendered image to choose samples from the domain of integration such that variance in the integral estimate is minimized. Importance sampling is a variance reduction technique that draws samples using a distribution that has the same shape as the function being integrated. This means that we are more likely to choose samples which will make a large contribution to our estimate. In this assignment you will explore various approaches for sampling irradiance on scene objects due to an infinite area light source (environment light) and explain why and when certain approaches are preferable to others. Background Reading Read Chapters 13 (especially 13.5), 14 (especially 14.3) and 15 (especially 15.6.5) in the pbrt book. This assignment will require a solid understanding of importance sampling, so please read these chapters carefully. Important Notice: Older versions of the pbrt book have a typo in the multiple importance sampling equation on page 676. The code in core/transport.cpp is correct, but the equation given in the book is wrong. Instead of multiplying both summations by the factor 1/( n f + n g ) , the first summation (sum over samples drawn from a PDF from f ) should be scaled by 1/ n f . The second summation should be scaled by 1/ n g . Part 1 – Basic Monte Carlo Integration Question 1 : Write a program to verify numerically that = (4 x 2 0 2 ) 1/2 dx . Use the Monte Carlo method and 2500 random numbers. Part 2 – Importance Sampling an Infinite Area Light In the real world, light incident on an object comes not just from light emitters, but is reflected or scattered from all directions. One way of approximating this effect in pbrt is to use an environment light (infinite area light), which defines light entering the scene from all directions due the surrounding environment. Environment lighting can greatly enhance the realism and richness of your renderings. However, since computing
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This note was uploaded on 10/21/2011 for the course CSCI 5108 taught by Professor Interrante,v during the Spring '08 term at Minnesota.

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Program3 - CSci 5108: Programming Assignment #3*...

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