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Bullet Ray Vision. Lee A. Butler US Army Research Laboratory Abe Stephens University of Utah SCI Institute. Genesis. Contract to MAGI in 1966* Observation: projectiles passing through matter have similarity to photons passing through lenses.

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bullet ray vision

Bullet Ray Vision

Lee A. Butler

US Army Research Laboratory

Abe Stephens

University of Utah

SCI Institute

genesis
Genesis
  • Contract to MAGI in 1966*
    • Observation: projectiles passing through matter have similarity to photons passing through lenses.
  • MAGI later developed Synthavision and did most of the rendering for TRON(1982).
background
Background
  • Photon transport was adapted to ballistic penetration. The threat replaced the photon. The target replaced the lens.
  • Ballistic penetration is like participating media. As the penetration occurs, there is interaction with the target media. Both the threat and the target are affected by the interaction.
  • Computation is performed on the entire ray/object intersection, not just at the surface.
    • CSG was a natural geometric representation.
original design
Original Design
  • Everything is expensive to compute, so allow everything to be re-used
    • Ray-geometry intersection was computed and saved for re-use. Typically, penetration equations and parameters were altered for each use.
    • Assumes a single ray/threat relationship.
slide5
THOR
  • V50:Velocity at which 50% of fragments will penetrate:

V50(ft/sec) = 10c (h(in) Af(in2))

Wf(grains) sec 

  • Residual Velocity:

Vr(ft/sec) = V(ft/sec)– 10c (h  Af) 

Wf sec  V(ft/sec)

  • Residual Weight:

Wr(grains) = Wf– 10c (h  Af) 

Wf sec  V

cultural evolution
Cultural Evolution
  • Programmer-user to Application-user.
  • Data re-use to application re-run.
  • Single ray/threat relationship to multiple rays/threat relationship.
  • Ray tracing slow to fast
one step forward
Interleave ballistic penetration calculations with ray/geometry intersection using classic BRL-CAD ray-tracer on CSG geometry.

Nice performance improvement, but still slow.

One Step Forward

View Computation Time (seconds)

two steps forward
Bullet Vision:

Since we’re ray tracing, render the results of the computation too. Free visualization!

Two Steps Forward
three steps forward
Implement computation as a shader in Manta packet-based ray tracer.

Need to collect in/out pairs before “shading.”

What was a batch application is now interactive. 3.9 fps on Intel Core 2 2.66Ghz with 4 cores.

Surprise: BVH Traversal is the major bottleneck in the system. “Shader” with 14 exponentiation operations is distinct second.

Three Steps Forward
future work
Future Work
  • Current work is a brute-force implementation of the penetration equations. 14 exponential operations.
  • There is ample opportunity to optimize the computation of the equations.
  • This is a equation fit to measured data. Alternative equation fits that are more computationally friendly are possible.
future work1
Future Work
  • BVH acceleration structure may not be optimal for applications where “transparent” geometry is the norm. Some further investigations on acceleration structures for such applications is needed.
  • Current frustum acceleration techniques may not be optimal for transparency and deferred shading algorithms.
funding
Funding

US Army Research Laboratory

The Center for the Simulation of Accidental Fires and Explosions

(C-SAFE) B524196