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View Full Version : Voxel Distance Between Particle request



Mr Rid
07-02-2007, 11:16 AM
1. Can we please have a single, global Distance Between Particle parameter in the particle Size and also as a Blending option in Voxels? This would eliminate the ever-present puffballs (volume) and marbles (surface) syndrome. The biggest problem is when particles separate and the Voxel sphere becomes blatant.

An example of what we've been missing. Two instances of the same particle sim, one shaded with typical HV marbles and the other with RealFlow.
http://www.box.net/shared/static/bzqlpzm9rt.mov

The current X/Y/Z Distance Between Particle gradients dont seem to work in the Dissolve, Color, Luminosity, or Opacity. They do however effect the Density, Thickness, Texture Amplitude and Velocity (already reported the bug), but they tend to have an undesirable sharp falloff and ignore Linear keys. Even if they worked properly, it is tricky to layer each axis separately in a combined effect when a single, global Distance Between Particle would be easier to apply and more often needed for typical liquid and smoke FX.

But where the Distance Between Particle gradient would be the most effective is in the Blending and Particle Size!

The data seems to already exist in LW, so how hard is it to just associate an appropriate gradient?

2. A Blending value (0 to 100%) would also be most useful, rather than a single arbitrary value that is either on or off as it is now.

3. It's also time that Voxels enjoyed the same rights as other objects in a scene like Light Exclusions, Alpha Channel options, and to be made Unseen By Camera.

MSherak
07-02-2007, 02:24 PM
I just have a comment.. Not that I don't agree with what you have posted about what is needed in HV..

Watching the animation what came to my mind is that if this was water, where is that volume of fluid disappearing to on the RF side?? I don't think I have ever see a fluid lose volume like this in real life.. I would think the combo of both would give you the fluid volume and movement that would look more realistic.. Course I think this could be achieved if you used spawning particles off the main.. That way you could mix the volumes the way you wanted.. Looks like RF is trying to attempt a look with only one pass to get it to look more pleasing to the eye where this attempt would looks strange in HV.. Try the spawning and I bet you could get the HV side to look better..

Just my .02

toby
07-02-2007, 05:53 PM
It's an improvement, but I bet you it would generate a lot of complaints the way it pops, and because it's still pretty inferior to real fluid sim. I guess it would be handy tho. LW does need a LOT of improvement in this area too.

Mr Rid
07-02-2007, 07:17 PM
I just have a comment.. Not that I don't agree with what you have posted about what is needed in HV..

Watching the animation what came to my mind is that if this was water, where is that volume of fluid disappearing to on the RF side?? I don't think I have ever see a fluid lose volume like this in real life..

Just my .02

Actually, you have. This simple RF example more accurately approximates the apparent bahavior of a water splash. Bear in mind that was only a low particle sim to save time. If you wanted more volume, use more particles, and 'crowd' self-interaction to maintain viscosity. You dont want to 'maintain volume' as ONE particle moves off by itself. It is better to have nothing, or a very tiny bead render around a single point venturing off on its own. But right now, we are stuck with cartoonish beach balls.

And with smoke sims you wind up with individual cottonballs drifting around. Where particles inevitably thin out, you want to see less defined volume. With smoke you might use the Distance Between Particle to make the volume larger instead of smaller (as with a liquid), and use lower thickness/more dissolved/less opacity so it becomes hazier (like in Dynamite)... instead of a solid cotton wad floating around as we currently have to contend with.

But with a realistic liquid sim, LW can not deal with enough particles to maintain volume without looking like a bunch of marbles where particles are more sparse. For really convincing fluid you really need hundreds of thousands to millions of particles. A 90 frame sim with 20,000 self-interacting particles took over 3 hours to calculate (30,000 totally choked LW).
http://www.box.net/shared/static/xy53myje2k.mov
This would take only a few minutes in RF, but I am not asking LW to compete with RF's speed. But 20,000 is nowhere near enough particles to escape the marble syndrome. So what would help tremendously instead is to be able to make those marbles or cottonballs less apparent as they spread out. Distance Betweeen Particle could be used to shrink, flatten, dissolve or otherwise downplay the inherent voxel spheres, not to mention creating a more cohesion-like stretch in the blend between separating particles.

Mr Rid
07-02-2007, 07:48 PM
I think a mistaken assumption about the examples is that one particle should roughly equal a single drop of water. The whole point of particle shaders is to cheat say a clump of 10 particles to represent 100s of drops of water in reality. 100 particles are to represent 1000s of drops. It is not practical to have a particle for each drop of water. You would need hundreds of thousands to millions of particles which is impratcial to deal with, especially in LW (look to ILMs work on Poseidon for insane particle counts).

When you have say a handful of particles in LW, HV renders a larger volume around them to fake the appearance of a volume of water. But when particles separate, or one particle heads out on it's own, the cheat is suddenly apparent. One particle continues to represent dozens or hundreds of drops of water, but it looks ridicluous as this single fat, perfectly round sphere.

A Distance Between Particle parameter would smooth that transition from volume of water to drop of water.

Mr Rid
07-02-2007, 08:32 PM
It's an improvement, but I bet you it would generate a lot of complaints the way it pops, and because it's still pretty inferior to real fluid sim. I guess it would be handy tho. LW does need a LOT of improvement in this area too.

The slight popping is because this is a simplified example sim where RF is using a sequence of barely adequate rez meshes. HV shouldnt have any popping since it does not use polygons changing each frame.

And you think RealFLow is an inferior fluid simulator?!

toby
07-02-2007, 09:09 PM
No I've seen great fluid sim from Realflow, not even counting Guardian, which I haven't seen. But I don't think the good stuff is based on particles, except maybe for spray.

js33
07-02-2007, 09:41 PM
I read an article, well skimmed it really, in Computer Graphics mag about the wave simulations for the movie Surf's Up and they used a mesh for the main waves and then particles for the splashing parts and edge of the wave in Maya.

Can anyone simulate a wave like that in LW?

Mr Rid
07-02-2007, 11:10 PM
Check out The Guardian. I understand that morphs were used to cotrol the waves to rise and fall on exact cue.

An ocean I did in a day with only procedurals for a cheap movie back in 2000 (LW 5.6).
http://www.box.net/shared/static/4nnvnomvtt.mov

js33
07-03-2007, 12:01 AM
Hi Mr. Rid,

That's not bad but I was thinking of pipeline waves that roll and break as they approach the shore. Is that type of wave possible in LW?

toby
07-03-2007, 12:24 AM
I'd like to see Guardian for the fx, but I just know I'd hate the rest of it, and I've just seen two crappy movies recently.

Jenn (somebody), 'Celshader' here on the forums did a lot of the Guardian waves if not all. Mostly RealFlow, reprogrammed-in-python or something like that. But yea I guess big, rolling waves doesn't make sense to simulate.

Here's my ocean effort, from my schooldaze back in '01
http://www.box.net/index.php?rm=box_v2_download_shared_file&file_id=f_74376019

toby
07-03-2007, 12:44 AM
Hi Mr. Rid,

That's not bad but I was thinking of pipeline waves that roll and break as they approach the shore. Is that type of wave possible in LW?

Doing it manually, like modeling morphs, would be the only way. It probably wouldn't be practical to simulate it in any package, imagine trying to simulate tons and tons of water getting pushed up as high as a house and over, and have it continue down the beach - where would you start? Well, I'm sure Jenn would know, but as far as LW, it doesn't have fluid sim anyway

Phil
07-03-2007, 12:57 AM
[email protected]

It's the only way to get these kind of requests on to NewTek's radar. The same is true for all of your other requests and comments. You can then share the case ID for each request so that others can contribute.

Mr Rid
07-03-2007, 01:09 AM
Hi Mr. Rid,

That's not bad but

Mmm, yes it is.

js33
07-03-2007, 04:57 AM
I'd like to see Guardian for the fx, but I just know I'd hate the rest of it, and I've just seen two crappy movies recently.

Jenn (somebody), 'Celshader' here on the forums did a lot of the Guardian waves if not all. Mostly RealFlow, reprogrammed-in-python or something like that. But yea I guess big, rolling waves doesn't make sense to simulate.

Here's my ocean effort, from my schooldaze back in '01
http://www.box.net/index.php?rm=box_v2_download_shared_file&file_id=f_74376019

Hi Toby,

That was some nice looking water. I was getting sea sick. :D

Well the waves I'm talking about are the ones created for the movie "Surf's Up". http://www.apple.com/trailers/sony_pictures/surfsup/teaser_high.html

Man there sure have been a lot of animated penguin movies lately.

js33
07-03-2007, 04:58 AM
Mmm, yes it is.

I was thinking it looked a little dated rather than bad.

toby
07-04-2007, 04:14 AM
Hi Toby,

That was some nice looking water. I was getting sea sick. :D

Well the waves I'm talking about are the ones created for the movie "Surf's Up". http://www.apple.com/trailers/sony_pictures/surfsup/teaser_high.html

Man there sure have been a lot of animated penguin movies lately.
Why thank you sir!

Interesting clip! The water fx look excellent, but there's no way I'm going to see this anytime soon, the characters look crummy, and I'm pretty sick of animal-cg movies.

I'll bet you anything those waves were done the way mr. Rid said, manually.