Pyro/Smoke Render

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So I've got this pyro fx explosion I made in Houdini FX 15.0.416 (not indie or apprentice). I followed the “Pyro Explosion Shader” tutorial video to as musch as I could (https://www.youtube.com/watch?v=fTIeGob0Wuo), [youtube.com] but his explosion was made using Houdini Apprentice 13, and from what I've read a lo has changed since then (most notably the Shader looks to have been completely rebuilt and rearranged).

Here's my animation:
https://youtu.be/Awo6XcjLuoQ [youtu.be]

…and my project file if you're so inclined:
https://www.dropbox.com/s/qme0t7qq9lz2xws/Explosion_Test_v2.hip?dl=0 [dropbox.com]

A couple questions:

1. Why does there appear to be a small grid-like pattern on my animation? Did I not set my division size small enough? (You'll see it's at 0.05)

2. when rendering a TIFF sequence, the color/luminance of the frames looks quite different than the PNG sequence (this video was made from the PNG sequence). The PNG's come out much more contrasted and saturated than the TIFF's, and the settings in Render tab are quite sparse, so I couldn't figure out if it was a compression thing or a color space setting..

Any help is welcomed and appreciated, thanks guys!
Edited by slavensb - July 17, 2016 22:00:26

Attachments:
Explosion_Test_v2.hip (918.4 KB)

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Hi slavensb,

1.
The gird pattern truly has to do with the resolution of your sim.
The actual value has no true meaning without the Size of your Simulation Container.
It just meas that it will acutally split a 1 Unit length by 0.05. (so 20 Voxels per side)
So if your fire is small those are not a lot of values to sample from.
On the otherhand, if you have a 100m Smoke Column in the same framng you now have 2000 values to sample from.

2.
Are you sure you are interpreting both renders in the same colorspace?
Otherwise I am not sure where the problem stems from.

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1. Grid like pattern could also be caused by the box setting on the Volume Filter parameter with a filter width of 1 on the import_pyro Object containing the volumes to render. Try setting the Volume Filter to Gaussian with a value of 1.2.

Box filter works well when you have a very high resolution volume where the voxel size in the original volume container is quite a bit smaller than the final rendered pixel in the output image.

2. Depending on the render target, Houdini may apply or not apply a corrective gamma of 2.2. Tiff is output in linear space. Try applying a gamma of 2.2 either in the display settings to see if this gets the png's close to the tiff.

Are you using Mplay to preview the sequence? Have a look at the gamma parameter at the bottom right.
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