Real-Time Ray Tracing3D Modeling of the Future

Marissa Hollingsworth Spring 2009

OBJECTIVES

• Current method: Rasterization• What is Ray Tracing?• Ray tracing Algorithm• Applications• Why ray tracing? Why not?• Conclusions• Questions?

Current Method: Rasterization

• Current leader for rendering 3D graphics

• Implemented on most standard GPUs– Meaning speed and efficiency

• Takes one triangle at a time, projects it to the screen and paints all covered pixels– linear complexity with respect to scene size:

– Requires additional shading/shadow/texture algorithms

What is Ray Tracing?

• Technique for rendering 3D graphics• Accurately imitates properties of

light rays–Reflection, Refraction, Shadows

• Allows for global illumination

http://www.oyonale.com/modeles.php?lang=en&page=40

Ray Tracing Algorithm

Viewpoint

Image

Light Source

Scene Object

1.Scene Description

2.Ray Generation

3.Ray Traversal

4.Object intersection

5.Shadow rays

6.Recursive reflection and refraction rays

7.Pixel coloring

Applications: Video Games

Oasen Quake III

•Collision detection using rays

•Simple code for realistic effects

•First game using ray tracing

•Complex illumination model for daytime, weather conditions etc.

Interactive Global Illumination

• Simulating global lighting through tracing rays• Greatly increases realism by adding global lighting

effects

Wald, I., Kollig, T., Benthin, C., Keller, A., and Slusallek, P. 2002. Interactive global illumination using fast ray tracing.

With Without

Massive Modeling

Can render entire CAD

models without

simplification

Scales logarithmically with scene size

Why Ray Tracing?

• Highly realistic images• Physical correctness and dependability• Ease of implementation• Highly efficient–Parallel computations

• Ray reuse (i.e. distance detection)

VW Beetle With Correct Shadows and ReflectionsSlusallek, P., Shirley, P., Mark, W., Stoll, G., and Wald, I. 2005. Introduction to real-timeray tracing. In SIGGRAPH '05: ACM SIGGRAPH 2005 Courses. ACM, New York, NY, USA,1.

Why Not?

• Slow rendering times

• Not fully supported in hardware…yet

–Mostly implemented in software

–Programmable RPU (Ray processing unit)

• Computationally expensive!

Summary

• Ray tracing renders highly realistic 3D models

• Allows for efficient computations, but SLOW

• Many useful applications

• Not feasible for real time implementation in

near future…but eventually!

QUESTIONS?