CS 148, Summer 2012 Introduction to Computer Graphics and Imaging Justin Solomon

http://www.futuretech.blinkenlights.nl/misc/scene_1024x768.jpg CS 148, Summer 2012 Introduction to Computer Graphics and Imaging Justin Solomon

http://www.publicdomainpictures.net/view-image.php?picture=female-photographer&image=4360&large=1 http://bloodredpencil.blogspot.com/2010/09/need-help-get-help.html

http://www.publicdomainpictures.net/view-image.php?picture=female-photographer&image=4360&large=1 http://bloodredpencil.blogspot.com/2010/09/need-help-get-help.html

http://software.intel.com/file/37491

Light source http://software.intel.com/file/37491

Light interacts with objects in scene http://software.intel.com/file/37491

Image plane http://software.intel.com/file/37491

?? http://software.intel.com/file/37491 Most light doesn t reach the camera

?? http://software.intel.com/file/37491 Most light doesn t reach the camera

Many lighting effects are reversible

Trace rays from light to camera

Trace rays from light to camera

Draw viewing ray through each pixel

Intersect with geometry

Compute light ray

Evaluate shading µ

Take closest one

µ µ Redirect ray

µ µ Redirect ray

Rasterization for (each object in scene) drawobject();

Rasterization for (each object in scene) drawobject(); Ray Tracing for (each pixel in image) sendray();

Rasterization for (each object in scene) drawobject(); Ray Tracing for (each pixel in image) sendray();

for each pixel do compute viewing ray if (ray hits an object with t>0) then Compute normal Evaluate shading model else Set pixel color to background color Textbook page 85

~d = direction ~o = origin Ray

~d = direction Does not have to be unit length! ~o = origin Ray

t 1 t 2 (0; 1) ~o + t ~ d Point on Ray

~o + t ~ d t < 0 Point on Ray

~o + t ~ d t < 0 Point on Ray

No perspective transformation needed! ~j ~p 0 ~p = ~p 0 + u~i + v~j u 2 [0; w]; v 2 [0; h] ~i Generating rays

k~x ~ck 2 = R 2 ~o + t ~ d Ray-object intersection

~o + t ~ d k~x ~ck 2 = R 2 Ray-object intersection

~o + t ~ d k~x ~ck 2 = R 2 k~o + t ~ d ~ck 2 = R 2 Ray-object intersection

~o + t ~ d k~x ~ck 2 = R 2 k~o + t ~ d ~ck 2 = R 2 (~o + t ~ d ~c) (~o + t ~ d ~c) = R 2 Ray-object intersection

~o + t d ~ k~x ~ck 2 = R 2 k~o + t d ~ ~ck 2 = R 2 (~o + t d ~ ~c) (~o + t d ~ ~c) = R 2 k dk ~ 2 t 2 + 2((~o ~c) d)t ~ + k~o ~ck 2 = R 2 Ray-object intersection

Ray-object intersection CS 148, fall 2011

~x ~c ~ N = ~x ~c k k Normals

~v 3 ~N = (~v 2 ~v 1 ) (~v 3 ~v 1 ) k(~v 2 ~v 1 ) (~v 3 ~v 1 )k ~v 3 ~v 1 ~v 1 ~v 2 ~v 2 ~v 1 http://designjk.files.wordpress.com/2011/12/teapot-decorated.png Normals

~ l2 ~x ~ l1 ~x ~x Light rays

http://www.spot3d.com/vray/help/150sp1/images/examples/shadows/03_raytraced_colored.png

http://2.bp.blogspot.com/-2cpxosdtne8/t5nmclgobpi/aaaaaaaaaj4/xgaz168hpkg/s1600/p0008_i004.png Intersect light ray with scene

abstract class surface virtual hit-record hit(ray, t0, t1) virtual box bounding-box() struct hit-record vector3d position, normal surface hit-surface abstract class material color evaluate(in-ray, normal, pos)

color ray-trace(ray r) hit-record record = intersect(r); if (record.hit-surface.is-reflective) ray reflected-ray = reflect(r,record.normal); color reflected-color = ray-trace(reflected-ray); compute-spectral-component( reflected-color);

Lots of bounces Fewer bounces CS 148, fall 2011 Save time; avoid infinite recursion

http://www.deepakantony.com/wp-content/uploads/2012/04/ambientocclusion_instancing.png http://members.optusnet.com.au/pennywyatt/images/people.png Deal with repeated objects

Store object once, use often http://members.optusnet.com.au/pennywyatt/images/people.png Deal with repeated objects

Each instance stores a transformation matrix M (can stretch, rotate, etc!) Deal with repeated objects

M 2 R 3 3 Object coordinates World coordinates Deal with repeated objects

M 2 R 3 3 ~o + t ~ d Deal with repeated objects

Do intersection here! M 2 R 3 3 M 1 ~o + tm 1 ~ d ~o + t ~ d Deal with repeated objects

M 2 R 3 3 M 1 ~o + tm 1 ~ d Same t! ~o + t ~ d Deal with repeated objects

M 2 R 3 3 ~N ~ M ~ N Deal with repeated objects

http://upload.wikimedia.org/wikipedia/commons/8/8b/csg_tree.png Binary operations for shape

A B A [ B A B A \ B http://en.wikipedia.org/wiki/constructive_solid_geometry Binary operations for shape

A B A [ B A B A \ B http://en.wikipedia.org/wiki/constructive_solid_geometry Binary operations for shape

A B in(a) = [1; 3] in(b) = [2; 6] in(a \ B) = [2; 3] in(a [ B) = [1; 6] in(a B) = [1; 2) Store inside intervals

A B in(a) = [1; 3] in(b) = [2; 6] in(a \ B) = [2; 3] in(a [ B) = [1; 6] in(a B) = [1; 2) Store inside intervals

A B in(a) = [1; 3] in(b) = [2; 6] in(a \ B) = [2; 3] in(a [ B) = [1; 6] in(a B) = [1; 2) Store inside intervals

A B in(a) = [1; 3] in(b) = [2; 6] in(a \ B) = [2; 3] in(a [ B) = [1; 6] in(a B) = [1; 2) Store inside intervals

http://ps-2.kev009.com/catia-b18/basug_c2/basugbt1510.htm

http://www.hackification.com/2008/08/31/experiments-in-ray-tracing-part-8-anti-aliasing/

Scatter rays to make ray tracing less crisp.

Multiple rays per pixel

Moiré pattern http://upload.wikimedia.org/wikipedia/commons/f/fb/moire_pattern_of_bricks_small.jpg Multiple rays per pixel

Remove Moiré patterns http://en.wikipedia.org/wiki/file:moire_pattern_of_bricks.jpg

???

Hard shadows Soft shadows http://erich.realtimerendering.com/shadow_comparison.html

http://user.online.be/felixverbelen/lunecl.jpg Lights aren t all point sources

Randomly sample light rays

Shadow computed per ray

Shadow computed per ray

Shadow computed per ray

http://liam887.files.wordpress.com/2010/08/weaver.jpg

Square lens Focus plane Randomly sample eye positions

https://graphics.stanford.edu/wikis/cs148-11-fall/raytracingresults http://www.baylee-online.net/projects/raytracing/algorithms/glossy-reflection-transmission Randomly sample reflected rays

http://www.matkovic.com/anto/3dl-test-balls-01.jpg Randomly sample positions

Diffuse Ambient http://en.wikipedia.org/wiki/ambient_occlusion Brightness depends on nearby geometry

Account for indirect lighting http://en.wikipedia.org/wiki/global_illumination

Diffuse inter-reflection Account for indirect lighting http://en.wikipedia.org/wiki/global_illumination

Caustics Account for indirect lighting http://en.wikipedia.org/wiki/global_illumination

Value p b m Variable Pixels on screen Objects in scene Average pixels/object Rasterization: O(bm) Ray tracing: O(bp) Accelerated ray tracing: O(p log b) CS 148, fall 2011

http://sopra.le-gousteau.de/images/2/2e/bv_bvh_bspheres.jpg http://graphics.ucsd.edu/courses/rendering/2004/ssaha/index_files/finalbvh.jfif Bounding Volume Hierarchy (BVH)

http://algorithmicarts.com/images/2008/bsptree-cutaway1269x684.png Binary Space Partitioning (BSP) trees

Uniform subdivision grid http://www.cs.berkeley.edu/~sequin/cs184/imgs/spatialsubdiv.gif

[NVIDIA, SIGGRAPH 2008] Embarrassingly parallel, but not SIMD?

http://www.futuretech.blinkenlights.nl/misc/scene_1024x768.jpg CS 148, Summer 2012 Introduction to Computer Graphics and Imaging Justin Solomon