Project Raytracing

Content Goals Idea of Raytracing Ray Casting – Therory – Practice Raytracing – Theory – Light model – Practice Output images Conclusion

Specifications Ray tracer depends on how to represent objects Parametric equation for precision, not rapidity Develop a Ray Tracer in order to explore a new intersection algorithm Two teams : - for mathematics - for code

Main principle Create 3D pictures Mathematical equation Throw ray from eye to pixels Not FROM source light: TO it Number of reflections Great pictures but slow

Algorithms Ray casting - first method - no bounce Ray tracing - from eye to pixels - reflection - refraction - shadow

Fields of use Animation studio Pixar: with parsimony → light effects Video games → with triangles → faster and great

Ray casting For each pixel: ● Shoot a ray from the observer to the position of the pixel ● Test if the ray hits an object in the scene ● If there is a hit: the color of this pixel will be the color of the object ● If there is no hit: the pixel receives the color of the background

Ray casting What do we need ? ● A position for the observer (eye, camera) ● A direction/object to look at (and a « way up ») ● An object to show on screen ● A representation of the 2D screen in the 3D space

Ray casting

Our Ray Caster

From Ray Casting to Ray Tracing

We add : ● Lights ambient, diffuse, specular ● Shadows ● Reflexion => recursion : another ray is shot from the intersection ● Material properties ambient, diffuse, and specular coefficients

Lightmodel Used: Phong reflection model 3 types of light: ambient, diffuse, specular

Ambient and Diffuse

Specular

Shadows Only add diffuse and specular light, if a lightsource is visible Test for intersections between a point on the sphere and the lightsource

In practice ● Implementation of the ray casting algorithm ● From ray casting to ray tracing ● Demo, use cases ● Highlight of some interesting modules

From Ray Casting to Ray Tracing We add : ● Lights ambient, diffuse, specular ● Shadows ● Reflexion => recursion : another ray is shot from the intersection ● Material properties ambient, diffuse, and specular coefficients

Video link 1

Video link 2

Interesting modules ● Positionning of the screen in 3D space ● The RayTracer class ● That's the core of the program (light model) ● Shadows ● The use of inheritance to compute intersections ● Obtaining an animation ● Camera and lights movement ● Export a sequence of images, make a movie ● The Draughtboard

Difficulties - math libraries - C++, compilation, building environment - Screen implementation - Unexpected results (debugging)

Achievements Light effects Animation rendering Different shapes Antialiasing

Improvements Refraction and transparency Textures and noise Depth of Field Image mapping Bounding Volume Radiometry (power, energy, radiance...) Photon mapping

Thanks! Thank you for your attention!

Questions?

reims.fr/image/siRendu/Documents/2004- Chap5-BRDF.pdf tracing.gif?w=468