Question on Interpreting Exercise 2 from Chapter 2 (Geometry and Transformations)

[Kevin Zhang]

Hi all,

I was looking over the exercises from chapter 2 of the 3rd edition and saw exercise 2, which involved modifying the bounding box representation to involve arbitrary user-defined slabs. If the bounding box representation is modified, then should the way the ray intersection acceleration data structures also be modified? If so, I'm a little confused because ray intersection acceleration is covered later in chapter 4. Or, is the exercise just to implement the user-defined bounding box plus some useful functions, like intersection functions? 

Thanks, 
Kevin 

[Matt Pharr]

That’s a good question. Arguably that’s not a great exercise, in that, as you’ve discovered, it has a number of cascading implications throughout the rest of the system—rays are never intersected with the shape-reported bounding box directly but the bounding box is only used for building acceleration structures. It might be a better exercise if the acceleration structures did an intersection test with the shape bounds before doing a ray shape test.

Thanks,

Matt

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