Hair shading

[dictoon]

Features to support and points to investigate:

• Curve representation
  • Bezier splines? B-splines?
  • Flat camera-facing ribbons and actual 3D "tubes" (with optional caps)
  • Support for arbitrary per-vertex attributes
• Fast, memory-efficient ray-curve intersection
  • Intersection of static and moving curves
  • Can we do this analytically, without tessellating the curve into segments? Is it fast enough?
• Fast intersection of many curves
  • Acceleration structure: (S)BVH?
• Basic hair shading model: Marschner?
• Test scenes for correctness and regression testing
• Performance tests
  • Comparisons with Arnold and PRMan, with and without motion

[est77]

Bezier.

A possible starting point: http://wscg.zcu.cz/wscg2002/Papers_2002/A83.pdf

I'd add the possibility of generating curves at render time to the list.

[dictoon]

Yes, that paper was actually mentioned by Elvic. Direct intersection of curves would be very desirable, we just need to figure out if this is practical from a performance standpoint.

[pberto]

Shading wise we already have sadeghi (which is based on marshner and provides much better look and easier controls). We can share it so you can make an integrator. We have to think in OSL terms already.

[pberto]

Also please add to the specs that we need support for ribbon-like curves (cross section: line) and for thick curves (cross section: circular), in the last case we should also have a hemisphere at caps start/ending.

[dictoon]

Already there, I add the caps part, good point.

Franz

On Dec 16, 2012, at 5:54 AM, Paolo Berto notifications@github.com wrote:

Also please add to the specs that we need support for ribbon-like curves (cross section: line) and for thick curves (cross section: circular), in the last case we should also have a hemisphere at caps start/ending.

— Reply to this email directly or view it on GitHubhttps://github.com/jupiter-jazz/appleseed/issues/221#issuecomment-11414309.

[dictoon]

Hair shading implemented in #2132.