more 2d pyro examples

Here, while I tidy them up and think of more interesting examples for the wiki. :)

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Oh, and the flap one too, forgot that! Tho I think I left all the previous versions in each file, so the shockwav3d file has all the bits needed to recreated the earlier files.

Main thing thats interesting (to me anyway) was this was my first time playing with the pyro solver to do fire. Shows how much of an fx artist I am...

Getting it to work was easier than I thought, create a fluid source sop and on the container settings set it to the 'source fuel' preset. Within dops I made a matching source volume dop, and also set the initialise mode to 'source fuel'. With the default pyro settings, you get fire.

As I mention in the wiki, playing with it in 2d mode is the perfect way to get a feel for what the various controls do, as it runs between 10fps and 20fps, nice and fast. I found keeping temperature diffusion low helped get nice high frequency detail. Disturbance was the most important control for mid frequency motion, and you can dial in the size and amount easily with the block size and disturbance scale parameters. Shredding gives super high frequency detail, but it almost buzzes too much to be useful, I left it turned off mostly.

Interestingly I ended up not using turbulence much, which is the slider I normally use for smoke. I found for fire it gave a very recognisable procedural wiggle (like the old water effect in quake 1 which I loved, but didn't work here). 

Playing with the combustion settings was also interesting; I'd watched enough Jeff Wagner webinars and browsed a few odforce posts to have a vague understanding of what this did, but was cool to see it in practice. While pyro generally tries to keep forces balanced so there's no pressure instability (that's all the non-divergence stuff), combustion intentionally adds divergence. This means unstable pressure build up, which means outward explosions of pressure in the pyro sim. I could see why this'd be handy for big Michael Bay explosions, but on the scale I'm working, its almost too much, so tended to leave it dialed down low, or not on at all. Its the 'gas released' parameter that does the most work here; push it up to 30, you get an H bomb of pressure that overwhelmes the solve in under a second.

What else... oh, finding a way to visualise fire. Here I visualise temperature rather than density, no idea if that's the right thing to do or not, but I think it looks pretty cool. Mapping it to a 'black body' ramp, and really aggressively playing with the min and max points helped me get a nice punchy looking 2d fire. I remember reading some posts by people who come up with their own shading techniques, have to look those up.

Ok, enough rambling, if you have any questions, let me know.