Ray tracing is a technique for generating images by tracing the path of light through pixels and simulating interactions with virtual objects. It can produce highly realistic images but is computationally expensive. Ray tracing works by firing rays from the eye position through each pixel into the scene, determining the nearest intersected surface, then recursively firing reflection and refraction rays to calculate each surface's contribution to pixel color. Ray intersections are organized into a tree structure to track color contributions to each pixel. At each intersection, illumination models calculate surface color based on factors like normal, light direction, and whether shadow rays to lights are blocked.

1. Ray Tracing
Computer Graphics
Prepared by
Yogesh Jatin
Gupta
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2. Ray-Tracing
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3. What is Ray Tracing
• Ray tracing is a technique for generating an
image by tracing the path of light through pixels
in an image plane and simulating the effects of
its encounters with virtual objects.
• The technique is capable of producing a very
high degree of visual realism, usually higher
than that of typical scan line rendering methods,
but at a greater computational cost.
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4. Raytraced Images
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5. Ray Tracing Model
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6. Ray-Tracing Setup
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7. Ray Tracing from Eye
• Starting at the light position traces many rays that never
reach the eye. Thus the traditional ray-tracing method is
to start at the eye and trace rays back-wards to the sourc
e.
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8. Basic Ray-Tracing
• Ray tracing proceeds as follows:
– Fire a single ray from each pixel position into
the scene along the projection path
– Determine which surfaces the ray intersects and
order these by distance from the pixel
– The nearest surface to the pixel is the visible
surface for that pixel
– Reflect a ray off the visible surface along the
specular reflection angle
– For transparent surfaces also send a ray
through the surface in the refraction direction
– Repeat the process for these secondary rays
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9. Ray-Tracing Tree
• As the rays ricochet around the scene each i
ntersected surface is added to a binary ray-tr
acing tree
– The left branches in the tree are used to represen
t reflection paths
– The right branches in the tree are used to represe
nt transmission paths
• The tree’s nodes store the intensity at that su
rface
• The tree is used to keep track of all contributi
ons to a given pixel
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10. Ray-Tracing Tree Example
S3
S4
S1
S2
Projection
Reference Point
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12. Ray-Tracing Tree (cont…)
• After the ray-tracing tree has been completed
for a pixel the intensity contributions are accu
mulated
• We start at the terminal nodes (bottom) of the
tree
• The surface intensity at each node is attenuat
ed by the distance from the parent surface an
d added to the intensity of the parent surface
• The sum of the attenuated intensities at the r
oot node is assigned to the pixel
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13. Ray-Tracing & Illumination Models
• At each surface intersection the
illumination model is invoked to determine the
surface intensity contribution
L = LIGHT SOURCE
N= NORMAL TO SURFAC
E
H = LIGHT INTENSITY
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14. The Shadow Ray
• The path from the intersection to the light s
ource is known as the shadow ray
• If any object intersects the shadow ray bet
ween the surface and the light source then
the surface is in shadow with respect to th
at source
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15. Reflection
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16. Thank You!
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