Ray Tracing

1. CS32310 Assignment JacekKruszynski (jck6) Ray Tracing

2. In Computer Graphics Ray Tracing is a technique devoted to generate images where light behave as naturally as possible. It is a very powerful and simple algorithm that currently is possibly most commonly used. Abstract

3. Introduction: • Way it works • Other methods • Complexity • Methods in Ray Tracing: • The basic idea and ways of improving • Results and Conclusion: • Difficulties and ways to deal with them Plan of Presentation

4. “Ray Tracing is a technique for image synthesis: creating a 2-D picture of a 3-D world.” [1] Basically Ray Tracing is trying to simulate the real physical process of light transport in a virtual world that we create using computers for achieving most realistic images. What Problem Ray Tracing Addresses 1. Glassner 1993, p1.

5. Scanlinerendering and rasterisation: • Method used by current graphics cards which produce images by projecting objects without any sophisticated optical effects. • Ray casting: • Method often used in computer games which is similar to Ray Tracing where optical effects if used are very simplified for better performance. • Radiosity: • Is a global illumination algorithm that include bouncing off the light from other surfaces (diffuse spreading light) and produce most photo-realistic images. It is used when the time of computation isn’t so important like pre-rendered movies. Different Methods of Rendering Processes

6. Despite that the most basic Ray Tracing algorithm is very simple the amount of data (single rays) that need to be calculated is a very large problem. • With the resolution grows the amount of rays to trace so the computational problem grows as well. • Optical effects that are simulated make it even more complex problem: • Reflection • Refraction • Scattering • Chromatic Aberration Why Ray Tracing is computationally expensive

7. In Ray Tracing light is traced in backward direction compare to the real world where rays are traced from light source (computational problem): Basic Idea of Ray Tracing • It works by sending a ray of light from a imaginary camera/eye in a virtual world through each pixel of image/virtual screen. After the ray determine what surface was hit set the colour of the pixel to the value returned by the ray. Ray Tracing (graphics). Wikipedia.org.

8. To avoid a sharp edges of shadows we need to use other techniques like Distributed Ray Tracing or Stochastic Ray Tracing. Way to achieve that is to send more than one ray through a pixel in random part of it. Used for depth of field, motion blur, shadows and reflections. Lead to computational problem Ray Branching (Spawning)

9. Ray Tracing spend most of the time on computing intersections. Computing same functions slows it down. More objects on the screen more intersections to be done. More reflecting surfaces even more intersections. Computational Complexity

10. Way to speed up the Ray Tracing is to split the work between processors (parallel computation). Every ray is independent from the other (computational independence). Ways to Speed-Up

11. Ray Tracing as a relatively simple Global llumination technique produces high quality images. To produce a HQ image a number of different techniques needs to be incorporated. To close computational time in bearable boundaries further optimizations are needed. This is a still developing area. Ray Tracing a Method producing HQ images

12. Anti-Aliasing is a very expensive method to use, but the final effect is sometimes worth the effort. To avoid using anti-aliasing we can use Stochastic Sampling mentioned earlier. Anti-Aliasing An example of picture without a Anti-Aliasing or any other method. Cooksey. Antialiasing and Raytracing. Shows what should we see Shows rendering result Radiosity. Wikipedia.org.

13. Putting the texture map onto objects to add a surface detail, can imitate and give effects like: • Diffuse, Specular Colours, • Transparency controlled by value, • Bump Mapping. Texture Mapping for Speeding-Up

14. Glassner, A. S., 1993. An Introduction to Ray Tracing. 4th Edition. Academic Press Limited. Cooksey, C., 1994. Antialiasing and Raytracing. http://local.wasp.uwa.edu.au/~pbourke/miscellaneous/aliasing/ (Accessed: 17.11.2009). Distributed ray tracing. Wikipedia.org. http://en.wikipedia.org/wiki/Distribution_ray_tracing (Accessed: 17.11.2009). Radiosity (3D computer graphics). Wikipedia.org. http://en.wikipedia.org/wiki/Radiosity_%283D_computer_graphics%29 (Accessed: 17.11.2009). Ray Tracing. Siggraph.org. http://www.siggraph.org/education/materials/HyperGraph/raytrace/rtrace0.htm (Accessed: 17.11.2009). Rendering (Computer Graphics). Wikipedia.org. http://en.wikipedia.org/wiki/Rendering_%28computer_graphics%29 (Accessed: 17.11.2009). References