Online Assets:
Piano - tf3dm.com (Toki)
Rose - archibase.net (Toki)
Table/Rose Stem wood texture image (Valerie)
http://www.deviantart.com/art/Wood-texture- I-101021540 by ResurgidaResources
Cork texture image (Valerie) http://enchantedgal-stock.deviantart.com/art/Corkboard- Wood-
Cork-Composite- 49823242 by Enchantedgal-Stock
Music sheet image (Valerie)
http://markopolio-stock.deviantart.com/art/Sheet- Music-2- 61505294 by markopolio-stock
Created/Personal Assets:
Table geometry (Valerie): modeled in Maya
Cork geometry (Valerie): modeled in Maya
Jar (Valerie): modeled in Maya
Music sheet geometry (Toki): modeled in Maya
Background image (Valerie)
Scene Lighting:
For our scene lighting we used two 10.f x 10.f area lights to create a more outdoor/global
lighting effect. To decrease rendering time, we placed our scene in a minibox with the back and
front face omitted so that the background plane could show through. We sampled at 64 samples
per pixel.
Technical Contributions:
Photon gathering (Toki)
When the ray tracer queries for a sample color at an intersected point, we get the photons within
a certain radius from that point from the kdtree. We then treat each photon as a point light and
add up their contribution to the BRDF. To avoid splotchiness without having to send out a
prohibitively large number of photons, we use a relatively large radius to find points in the kdtree
(around 0.1), find the average radius r of the photons, and treat each photon as a point light
fixed at r with 1/r^2 attenuation. Thus, even when the photons are sparse, we get smooth
lighting across the surfaces. The kdtree uses the Manhattan distance, which results in boxy-

looking patterns in the image, so we filter out the photons so they are all within the desired
Euclidian distance.
Colored Photon Mapping (Toki)
We extend photon mapping to keep track of colors by modifying the RGB-channel
lightIntensity variable that gets passed down the TracePhoton() path using a quick
heuristic. At each intersection, we generate a random number and test it against the three Ka
values of the material; any channel with a Ka value less than the random number gets zeroed
out in lightIntensity. Thus, a white photon that hits a pink object might either turn red (if the
random number is below Ka_r but above Ka_g and Ka_b) or remain white. The accumulation of
many photons at that point will hopefully be pink.
Refraction/Total Reflection for Photon Mapping (Toki)
If a material is transparent, we generate a random number, and if it is less than the intersected
material’s transmittance, we compute the refracted direction using the indices of refraction and
redirect the photon. Otherwise, if the random number is less than the sum of the material’s
transmittance and reflectivity, we reflect the photon.
Shadow Rays through Transmissive Objects (Valerie)
For transmissive objects, we modify the ComputeSampleColor function in the Backward
Renderer Class. Given an intersection with an object, we trace rays towards the light sources.
For each sample of a light source, we call the Trace function to see if the ray intersects an
object on its way to the light. If an object is hit that is not transmissive, then we know that the
point we are checking is in shadow, and we do not need to add any contributions to the BRDF
of that point. If an object is hit that is transmissive, then we continue to trace the ray towards
the light source by tracing an updated ray that starts a little beyond the intersection point. If we
never hit an object, then we add the BRDF of the sampled light source to the original
intersection point.
Depth of Field (Toki)
To get depth of field, we generate a ray for a normal pinhole camera and find the intersection of
that ray with the focal distance to get the focal point. Then we randomly sample from a circle
with a specified aperture radius at the camera lens, and return a ray that goes from the sampled
point to the focal point. Objects in the focal plane always stay in focus while others become
blurry.