Experiments in Projecting Computer Renderings
Onto the Surface of a Statue

CS99D: The Science of Art
Rahul Gupta, Daniel Perkel, Semira Rahemtulla, Alex Roetter

Background
In 1998, Professor Marc Levoy experimented with the idea of using a system of projectors to illuminate the surface of a free-standing statue. Specifically, by aligning a computer-generated image of the sculpture with the actual statue, Prof. Levoy was able to virtually alter the surface of the model. Thus, he could fool the eye into incorrectly interpreting the material of which the statue was composed. For example, an important visual distinction between plastic and metal is that the specular highlights on the latter are the color of the material, while those of the former are the color of the light source. By projecting a flat-shaded image onto the original geometry, then, it was possible to color the specular highlights, in effect causing the statue to be appear as if it were composed of metal instead of plastic. A web page describing Prof. Levoy's experiments can be found at /projects/lumiere/.

For our CS99D Final Project, we have re-implemented the projection system that Professor Levoy developed in the Stanford Graphics Lab. Furthermore, we have expanded upon its functionality by using a variety of shading mechanisms, by incorporating a virtual painting system, and by simulating the presence of ambient sources of light. This set of web pages is meant to help the user understand how our group implemented the projection system and used the available technology to incorporate a series of cool effects. We hope that the material on these pages is as interesting to you as the project was to us!

An Introduction to the Topics

While we can't actually bring you to the graphics lab where we designed our projection system, we can give you some insight into the models and equipment that we used for our project. Alright, this page's a leeetttllleee strange, but you'd be surprised what three months in Florence can do to you.

A major component of this project was the calibration of the individual projectors. In order for the rendered images to conform to the surface geometry of the statue, each projector needed to be appropriately calibrated based on its location in the room relative to the statue. As this web page explains, calibration involves inputting a projector's properties into a rendering program so that the image to be projected is positioned appropriately on the screen.

This web page outlines the concepts behind the program we used to render the various shaded images. It also discusses how a three-dimensional viewing program known as Scanalyze was used to produce the images, and how we employed the moviemaking tool Adobe Premiere to simulate the aging process of stone. The images produced by the shaders and the animation were eventually mapped onto the surface of the statue. Also listed here is an explanation of how we modified the location of the light source, and a short video clip from our presentation which demonstrates this effect.

Lastly, this web page describes the program we used to create a virtual painting system, providing a link to the original research and detailing an overview of the important features. A short clip from our presentation demonstrating the virtual painting system is included. Also provided is a video capture of the actual geometry of the statue. In this still, an image altered through Adobe Photoshop has been mapped onto the surface geometry.

Please direct all questions to one of the following:

Rahul Gupta Daniel Perkel Semira Rahemtulla Alex Roetter