Spheres in Arauna back

(L) [2008/10/07] [Phantom] [Spheres in Arauna] Wayback!

I added sphere support to Arauna:
[IMG #1 Image]
The code that intersects primitives is used for 16x16 packets, so an extra branch shouldn't hurt, I figured. The spheres are represented by regular triangles, but with a 'type' set to 'PRIM_SPHERE'; the field that normally holds the triangle normal then becomes the sphere centre. The vertices are abused for BVH construction: I add vertices for a virtual triangle that has the same aabb as the sphere. That way, no modifications to the BVH construction code where necessary. Sphere intersection  code is fully SIMD. Obviously, the sphere primitive is a great object for reflections (2 levels of recursion in this shot).

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[IMG #1]:

(L) [2008/10/07] [davepermen] [Spheres in Arauna] Wayback!

now arauna starts to get somewhere.. IT HAS SPHERES!!! a raytracer without spheres is not a real raytracer [SMILEY :)]
good work espencially for adding it so (close to) costfree. now some physics and let spheres roll!! [SMILEY :)] (let us shoot and drop spheres [SMILEY :)])

(L) [2008/10/07] [Phantom] [Spheres in Arauna] Wayback!

They are made for animation. I really want a demo with a bunch of balls rolling in Sponza, similar to what Dbevec did in that demo (Fiat Lux).

(L) [2008/10/08] [Shadow007] [Spheres in Arauna] Wayback!

Great work !
Could these spheres also be used for 'particle systems' as in fire, smoke etc ?
I thought also about spheres in Arauna, and thought it should be possible to create "air" spheres (as in with no reflection/reflraction), just Beer's law ...
What do you think about it ?
Did anyone here create ray traced 'particle system' effects ?

(L) [2008/10/08] [Stereo] [Spheres in Arauna] Wayback!

>> Shadow007 wrote:Did anyone here create ray traced 'particle system' effects ?
Yup, using old-school billboards with a lot of epsilon-related artifacts. Using spheres might result in better visual quality ...
Phantom: Love the screenshot!  [SMILEY :thumbsup:]

(L) [2008/10/08] [Phantom] [Spheres in Arauna] Wayback!

That particle idea might work.
What I tried before btw is this: Spawn a ray from the camera to the particle position (single point); if it is visible, draw an additive sprite ('flare'), otherwise don't. Improve it slightly by keeping track of the flare size in the previous frame, so you can fade it out softly. This works fine for sparks, although they don't show up in reflections, obviously.

(L) [2008/10/09] [Shadow007] [Spheres in Arauna] Wayback!

If you went for the "spheres as particles" goal, there is one paper that I had read that inspired me and that shows the advantages of spheres over billboards (although on a rasterizer) :
[LINK http://www.iit.bme.hu/~szirmay/firesmoke.pdf]
There would still be a problem : hard shadows for "soft" particles ... Shadow tests could not be simply be stopped at the first intersection, but once a certain total opacity is met. (Standard triangles and spheres would of course have an opacity of 1)...