CS6620 Assignment6

From Dangerski

[edit] Assignment 6 Add Acceleration Structures

[edit] BVH

I chose to implement the BVH. I tried a couple ways of splitting up the objects per node. Render times are based on the given scene file(3 samples/pixel). The render times are done on my laptop with a bunch of other programs running so I could probably get them a little faster if I closed everything.

-Method 1: Cycle the axis being split on (e.g. x,y,z,x,y,z...) and splitting the bounding box down the middle of that axis.

Setup/Load time: 2.76 s
Render Time: 9.57 s

-Method 2: Cycle the axis being split and then sorting the centroids of the bounding boxes of that axis and choosing the median value. This tends to give a more balanced tree.

Setup/Load time: 2.95 s
Render Time: 11.1 s

-Method 3: Pick the axis of the longest side of the bounding box and then splitting the bounding box down the middle of that axis.

Setup/Load time: 2.87 s
Render Time: 9.99 s

-Method 4: Pick the axis of the longest side of the bounding box and then sorting the centroids and picking the median.

Setup/Load time: 2.94 s
Render Time: 10.7 s

I also added the optimization of stopping the intersection tests if the current T value is closer than the BVH node.

I ended up using method 1 since it was the fastest and it turns out is the simplest to implement. I chose not to use any vector storage classes to speed up my BVH. I allocate 1 array of object pointers and then just store pointers in the BVH nodes. For the MPM data sets I had to set the radius of the spheres to small values like 0.0003 and 0.0002.