Pre-build Octrees?

[LaidlawFX]

Is there a means to pre-build your octrees so it just loads at render time and does not create it?

I barely grasp the concept of an octree, but some Mantra specific info would be quite helpful. Anything to shorten my render times is always a great thing to learn. My houdini help docs search draw a zero, and the odforce search draws 17 hits for me, now 18 probably after this.

[el_diablo]

Is there a means to pre-build your octrees so it just loads at render time and does not create it?

I barely grasp the concept of an octree, but some Mantra specific info would be quite helpful. Anything to shorten my render times is always a great thing to learn. My houdini help docs search draw a zero, and the odforce search draws 17 hits for me, now 18 probably after this.

I actually had an idea that application should build and update space residency structures while modeling/animating... could be used for many things. For your specific question, I dont have an answer though. Just wanted to throw the concept out there.

[LaidlawFX]

A couple months latter I found the nugget I was looking for from the help documents in 11. Hope this helps someone else who stumbles across this.

Ray Tracing Acceleration - KD-Tree and Bounding Volume Hierarchy

A ray tracing accelerator is a spatial data structure used to optimize the performance of ray intersection tests against complex geometry."kdtree" – Ray trace using a KD-Tree. Normally, the KD-Tree will produce the fastest raytracing performance at a modest initialization time. It is possible to control the performance/quality tradeoff for KD-Tree construction with the vm_kdmemfactor setting.

"bboxtree" – Ray trace using a bounding volume hierarchy. Sometimes a bounding volume hierarchy will be faster to construct and/or faster to raytrace than a KD-Tree.

KD-Tree Memory Factor - Change the memory/performance trade off used when constructing

KD-Tree acceleration data structures. Values larger than 1 will cause mantra to use proportionally more memory and take longer to optimize the tree in an attempt to make ray tracing faster. Smaller values will cause mantra to use proportionally less memory and take less time to optimize the tree while possibly compromising ray tracing performance. The default value of 1 will try to balance the amount of memory used by ray tracing data structures with the amount of memory used by geometry.

If you are noticing long tree construction times (in IPR, the render view pane hangs for a long time in the “Building Octree...” Phase), try decreasing the KD memory factor 0.1. If your render is too slow after tree construction, increase the value until you find a good balance of tree construction time vs. render performance.

-You can also notice the "Building Octree..." when you crank up your verbose settings if you are not going to IPR(Render View)

Edited September 22, 2010 by LaidlawFX

[smaugthewyrm]

thanks for this. i was just wondering about the octree waits.

would have just clicked the 'thanks' button...

oops no button. lol.