Ray tracing, regarding Turner Whitted's original paper

In summary, Turner Whitted introduced ray tracing in 1979 with his paper titled "An improved illumination model for shaded display" which can be found on the ACM digital library. In this paper, he discusses vector calculations in part 2 and specifically mentions vector V' which is scaled by | V . N |. The purpose of this is to make V' the same "vertical height" as the unit vector N, and |V.N| represents the length of V multiplied by the cosine of the angle between V and N.
  • #1
alan_k
2
0
As many of you may know, ray tracing was first introduced by Turner Whitted in 1979 in a paper titled "An improved illumination model for shaded display" (can be found on ACM digital library).

On the 2nd page, in part 2 (Improved Model) there are a number of fairly simple vector calculations, unfortunately I can't understand what is vector V' (please refer to the attached screenshot), and why is it scaled by | V . N | ... I would like to ask for your thoughts on this :)

Thanks !

P.S.: unfortunately I can't attach the paper to my post, it is copyrighted by ACM and I think it would be illegal to do so.

EDIT: found a link to the paper from Drexel University here
 

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  • #2
The diagram shows you the vector (N + V'), as the "horizontal" dotted line ending at the top of the N vector.

So V' is the third side of the triangle with the other two sides N and (N+V'). Ini other words, V' is the V vector scaled to be the same "vertical height" as N.

Earller N was defined as the unit vector (i.e. its length=1) normal to the surface.

So |V.N| is the length of V, times the cosine of the angle between V and N.
 
  • #3
Hi AlephZero,

Thank you so much for your reply, I appreciate it.
 

Related to Ray tracing, regarding Turner Whitted's original paper

1. What is Ray Tracing?

Ray tracing is a computer graphics technique used to generate realistic images by tracing the path of light rays as they interact with objects in a virtual scene. This technique was originally introduced in Turner Whitted's 1980 paper, "An improved illumination model for shaded display".

2. What was Turner Whitted's contribution to Ray Tracing?

Turner Whitted's original paper introduced several important concepts in ray tracing, including the use of recursive ray tracing, the use of bounding boxes to accelerate intersection calculations, and the use of reflection and refraction in lighting calculations. His work greatly improved the realism and efficiency of ray tracing techniques.

3. How does Ray Tracing differ from other rendering techniques?

Unlike rasterization, which works by projecting geometric primitives onto a 2D plane, ray tracing simulates the behavior of light in a scene by tracing the path of individual rays. This allows for more accurate and realistic lighting and shading effects. Additionally, ray tracing can produce global illumination effects, such as reflections and refractions, which are difficult to achieve with other techniques.

4. What are the limitations of Ray Tracing?

One of the main limitations of ray tracing is its high computational cost. Since each pixel in an image must be traced individually, it can be a time-consuming process, especially for complex scenes. Additionally, ray tracing struggles with simulating certain effects, such as motion blur and depth of field, which require additional techniques to achieve.

5. How has Ray Tracing evolved since Turner Whitted's original paper?

Since the publication of Turner Whitted's paper, ray tracing has continued to evolve and improve. One major development was the introduction of Monte Carlo integration techniques, which allow for more accurate and efficient sampling of light paths. Additionally, advances in hardware technology have made real-time ray tracing possible, which has greatly expanded its applications.

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