rendering sand

[borisb2]

Hi.

For a job I'm rendering sand as point-particles. I'm using a regular spotlight to get proper selfshadowing which works fine. The problem I'm facing is that the particles are so sensitive to changes in the angle to the light, meaning since the sand is moving in frame it changes drastically from being blown out to completely dull, based on the angle between camera and spotlight.

I'm rendering the particles as disks. Is there any way to relax that behavior a little (changing normals?) or is the only way to improve that to render them out as spheres? Rendering as spheres looks even nicer of course, but increase the rendertime heavily (also RAM).

Or maybe there is another trick for rendering points with more consistent selfshadows?

Thanks for any help

[Macha]

Somewhere floating around Odforce is a technique to create soft selfshadows on hair using volumes. Perhaps that would work in your case, maybe even with points instead of disks. But, I would actually render spheres or cubes instead. I think that shouldn't take up too much memory, or is it really that many?

Maybe.

[jjstanley]

Have you tried sprites? I think they may work well for you.

[borisb2]

well I tried both spheres and sprites. Instead of just 1 minute rendertime (for about 300k disk-particles) it shoots either rendered as sprites or spheres to more than 5 minutes!

Maybe I can optimize/simplify sprites or spheres even further to decrease rendertime?

I'm facing another problem at the moment: The sand is hitting the ground and then stopping at collision. But the motion-blur-streak stays there even if the particles are not moving anymore? Do have to add a velocity-sop and set these velocities to 0?

Edited October 29, 2010 by borisb2

[loudsubs]

For the velocity motion blur problem, you might be able to use a point node, add velocity in particle tab, and key frame it from $VX, VY, VZ to 0 when you need to. I haven't tried what you are saying, but I've multiplied vx, vy, vz to enhance motion blur in the past, so it might work in reverse.

[borisb2]

For the velocity motion blur problem, you might be able to use a point node, add velocity in particle tab, and key frame it from $VX, VY, VZ to 0 when you need to. I haven't tried what you are saying, but I've multiplied vx, vy, vz to enhance motion blur in the past, so it might work in reverse.

have done exactly that in the meantime .. thanks!

Any more insights on how to proper render or optimize spheres/disk-particles?

Thanks again

[CeeGee]

Maybe you can look on this thread also

I made alot of examples

Sorry i didint saw that you start that thread

I meen big amount of particles is best to render with, deepshadow, and particles as points.

In this example i render splash particles 28mil with deepshadow

Edited October 30, 2010 by CeeGee

[borisb2]

I made alot of examples

Sorry i didint saw that you start that thread

Yeah, I remember your great examples. Thanks for that. But one your renderings (post #11 for example), you can see exactly that what gets me in trouble at the moment with our comp-guys. The temple on front left is far "duller" than the one on far right.. this has never been a problem in your case?

I mean, I totally understand the reason for that (normals/orientation of the disk-particles), I'm just asking if there's a way to improve that? Why is the rendering with spheres in my case taking up to 1000% rendertime compared to disk-rendering? (no pbr, just an hdr for reflection)

[sanostol]

i'm quite sure that this is caused by the normal of the point pointing to the camera. You can easily add a normal to Your points that is used for rendering.

Yeah, I remember your great examples. Thanks for that. But one your renderings (post #11 for example), you can see exactly that what gets me in trouble at the moment with our comp-guys. The temple on front left is far "duller" than the one on far right.. this has never been a problem in your case?

I mean, I totally understand the reason for that (normals/orientation of the disk-particles), I'm just asking if there's a way to improve that? Why is the rendering with spheres in my case taking up to 1000% rendertime compared to disk-rendering? (no pbr, just an hdr for reflection)