Why does the velocity add so much more size?

[Jordan]

Just looking at the FDX file size when im saving with and without velocity... my file with smoke and fuel is 1meg and with smoke, fuel and velocity is 10meg. same if my smoke and fuel is 10meg, adding velocity pushes it up to 100meg!
I would have thought the smoke and fuel are both a single float value while the velocity is a vector (3 floats) so if my smoke and fuel is 10meg then with velocity I should get 25meg. Why does velocity seem to add 6 times the data it should?
Im sure there is other stuff going on that i dont understand but it seems a huge price to pay to include velocity.

[jrand]

Interesting question. Velocity is actually 4, 3+length.

6 sides to a voxel?

Also Fluid Mapping is huge too and of course wavelet.

I would think that the size really isn't that big a deal it is the time it takes to write to disk that I would be more concerned about.

[Jordan]

you shouldn't need 4 floats for direction and length, a 3 value vector gives you direction and length. Unless you are using a 3 float unit vector and a length float, but this would just be a waste of space!

Well when you are looking at a 10 fold size increase on jobs that are going to take up 10Tb + then it does matter quite a bit!

[jrand]

True True esp. if you are using an origin, but it seems you might want to use a relative velocity, ie current step vector - last step vector, LOL, hell if I know. Until Kreso or Vjeko spills the beans we may never know.

10 tb - cool sounds like a dandy I'd sure hate to try and watch/create the preview! I would take forever. I have something you might want to try if you like (you may already have something similar, I don't know) I'll pm you.

I still think i/o is the biggest problem, not storage.

You can buy 20 tbs of WD Blacks for under $1600, I have a bunch of these raid-0 in my local. I can't believe how cheap this shit is now, last time I looked a 12tb ext raid was like $7800, and it wasn't all that long ago.

You can cheat a little, I have tested this and in certain limited cases it does work, you can with Krakatoa either create your own or steal a velocity from a lower density simulation. It sounds like you are doing a large pyroclastic or something not sure it would work in that particular case, have to try it I guess.

[sitnisati]

Hi Jordan,

Velocities add so much because they exsist in every voxels in the grid, in contrast to fire and smoke that are present in just some parts of the grid.
Also, velocity is 3x more data per voxel. We will try to halve this requirement it for FFX 3.0.

Kresimir