清华大学：《计算机图形学基础》课程教学资源（授课教案）光线跟踪，递归算法，光线求交

History of Ray Tracing(光线跟踪 In 1980, Whitted proposed a ray tracingmodel, include light reflection andrefraction effects. A Milestone ofComputer Graphics

History of Ray Tracing (光线跟踪) • In 1980, Whitted proposed a ray tracing model, include light reflection and refraction effects. A Milestone of Computer Graphics

? Turner Whitted , An improved illuminationmodel for shaded display, Communications ofthe ACM, v.23 n.6, p.343-349, June 1980http.//www.raytracing.co.uk/study/home.htmeEKted rau tracexcencisIntroductioSmuatingtheRealWorkRayTracnaovancedF)condusoIntroductionsinceitsprooostionn196ebvAnoelravtracinnthederdinrenunfobiefedAscnincreasinglymorwerfu, thelevel ofqualtyanddotalthatjeyedeowinesandmoreandmore.comple:sesbecomeavoilsbln1980,Turttedsuodel thathreedimertingtightrayneprocesofcasnot focus ontheWhttedmethodaioebut ratherusestasarefericepcintfromwhich.todemoneed in ray path tracing and related methods such asgobalJlumneticUse the lnks isted ontoolbars above to navipstethe sitecidktheBecbuttonbeandfolonthnavigation markers to be systematicalystepped through each page

• Turner Whitted ，An improved illumination model for shaded display， Communications of the ACM, v.23 n.6, p.343-349, June 1980. • http://www.raytracing.co.uk/study/home.htm

: After receiving his PhD from NCSU in 1978.Turner Whitted left for Bell Labs and proceeded toshake the CGI world with an algorithm that couldray-trace a scene in a reasonable amount of time: He only has 14 papers, and Ray tracing is his firstpaper

• After receiving his PhD from NCSU in 1978, Turner Whitted left for Bell Labs and proceeded to shake the CGI world with an algorithm that could ray-trace a scene in a reasonable amount of time. • He only has 14 papers, and Ray tracing is his first paper

NATIONALACADEMYOFENGINEERINGMEMBERSHIPWEBSITEmemberdirectoriesDr.J.Turner Whitted (Print This)Senior ResearcherPrimaryWorkInstitution:MicrosoftResearchElection Year:2003PrimaryMembership Section:05.Computer Science &EngineeringCountry:United StatesState:WAMemberType:MemberElection Citation:For contributions to computergraphics,notably recursive ray-tracing He was elected as member of National Academyof Engineering in 2003

• He was elected as member of National Academy of Engineering in 2003

RayTracing(光线跟踪. Introduction of ray tracing·Ray intersection(光线求交)shadows(阴影)Transparence and specular reflection(透明和镜面反射)textures(纹理)

Ray Tracing(光线跟踪) • Introduction of ray tracing • Ray intersection(光线求交) • shadows(阴影) • Transparence and specular reflection (透明和镜面反射) • textures(纹理)

Introduction of ray tracing: Ray tracing Because ofits effectiveness, ray tracing is awidely used and very powerful rendering(drawing) technique Why we see objects?. Light can be interpreted as a collection of raysthat begin at the light sources and bounce aroundthe objects in the scenes..We see objects become rays finally come into oureyes

Introduction of ray tracing • Ray tracing – Because of its effectiveness, ray tracing is a widely used and very powerful rendering (drawing) technique – Why we see objects? • Light can be interpreted as a collection of rays that begin at the light sources and bounce around the objects in the scenes. • We see objects become rays finally come into our eyes

Basic Idea of ray tracingThink of the frame buffer as a simple array ofpixels, with eye looking through it into the sceneFor each pixel, what can we “see"?a ray casting from the eye through the center of thepixel and out into the scene, its path is traced to seewhich object the ray hits firstcalculate the shading value of the pointby the Phong modelcontinue to trace the rayin the scene to achievereflection, refraction

Basic Idea of ray tracing • Think of the frame buffer as a simple array of pixels, with eye looking through it into the scene • For each pixel, what can we “see”? • a ray casting from the eye through the center of the pixel and out into the scene, its path is traced to see which object the ray hits first • calculate the shading value of the point by the Phong model • continue to trace the ray in the scene to achieve reflection, refraction

Introduction of ray tracing: Features- Easy to incorporate interesting visual effectssuch as shadowing, reflection and refraction,since the path of a ray is traced through thescene- Besides geometric primitives(such as spheres, cones, cubes)easy to work with a richerclass of objects, includingpolygonal meshes, compoundobjects

Introduction of ray tracing • Features – Easy to incorporate interesting visual effects, such as shadowing, reflection and refraction, since the path of a ray is traced through the scene – Besides geometric primitives (such as spheres, cones, cubes), easy to work with a richer class of objects, including polygonal meshes, compound objects

Recursive Ray Tracing

Recursive Ray Tracing

Recursive Ray TracingIntersectcolor( vBeginPoint, vDirection){Determine IntersectPoint;Color = ambient color;for each lightColor += local shading term;if(surface is reflective)color += reflect Coefficient *IntersectColor(IntersecPoint, Reflect Ray);else if ( surface is refractive)refract Coefficient *color +=IntersectColor(IntersecPoint, Refract Ray);return color;1

Recursive Ray Tracing IntersectColor( vBeginPoint, vDirection) { Determine IntersectPoint; Color = ambient color; for each light Color += local shading term; if(surface is reflective) color += reflect Coefficient * IntersectColor(IntersecPoint, Reflect Ray); else if ( surface is refractive) color += refract Coefficient * IntersectColor(IntersecPoint, Refract Ray); return color; }