Bullet Ray Vision

1
Bullet Ray Vision

• Lee A. Butler
• US Army Research Laboratory
• Abe Stephens
• University of Utah
• SCI Institute

2
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).

3
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.

4
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.

5
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?

6
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

7
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.

Ray Depth Top Right Front A35
Full 9.22 10.52 6.27 12.36
Adaptive 7.30 10.54 3.15 7.60
View Computation Time (seconds)
8
Two Steps Forward

• Bullet Vision
• Since were ray tracing, render the results of
  the computation too. Free visualization!

9
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.

10
Interactive Rendering

• Watch Video

11
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.

12
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.

13
Funding

• US Army Research Laboratory
• The Center for the Simulation of Accidental Fires
  and Explosions
• (C-SAFE) B524196