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General Category => General Anim8or Forum => Topic started by: Blick Fang on February 01, 2014, 04:45:41 am

Title: Simulate heat
Post by: Blick Fang on February 01, 2014, 04:45:41 am
Hi All

Anybody have a method for simulating heat; i.e.   jet idling down a runway with the heat blurring but following the jet?

Cheers!
Title: Re: Simulate heat
Post by: ENSONIQ5 on February 01, 2014, 07:05:35 am
This old animation of mine includes the closest I have managed to come to this effect.  Unfortunately it wasn't done in Anim8or.  The method involved applying 'metaballs' (spherical objects that merge and blob together when close enough to each other) to a streaming particle effect, and using a refractive transparent material, and there was a fair bit of post-rendering frame-by-frame editing as well.  Within Anim8or, I'd have a play around with ART materials and bump-mapping on (perhaps) concentric rotating cylinders, or something like that.  Requires experimentation, or it might be that frame-by-frame editing is your best bet.

Title: Re: Simulate heat
Post by: kreator on February 01, 2014, 09:03:52 am
Hello Guys...

Ensoniq5: Tony, I remember that , from Metaballs you presumably mean Carrara`s Metaballs which can simulate a lot of effects

Blick fang: Andy, You could use terranim8or`s particles to get near on the same effect with all the particles close together as a transparent material.

But whichever way you go the will be some post processing involved.

Me thinks that will be a future article in the Anim8or Book (http://www.anim8orworld.com/Forum/index.php?topic=274.0)
Title: Re: Simulate heat
Post by: Blick Fang on February 01, 2014, 03:48:56 pm
Hi Guys

ENSONIQ5:  that is precisely what I was looking for!

kreator:  I will keep my eye out for it!  ;-)
Title: Re: Simulate heat
Post by: cooldude234 on February 02, 2014, 12:46:38 am
What you see that you call heat. Is actually the expansion of the atmosphere. As heat causes particles to be more energized (well that's what heat is, energy) those particles move around more, and the forces (gravity) holding them together become more over powered. Thus the particles become more spread apart.
So heat = particles spreading apart because of it energizing AKA expansion.

Now when see this in the atmosphere, whats happening is that light going through the heated area is being magnified (from the way gravity is effecting the photons passing through the less dense area). Which causes that 'heat' look.
This is why when the sun is around the horizon especially on a hot day, tends to look bigger. It also gets redder because the light is weakened as it passes through more atmosphere (the light itself looses energy).

Now in video games/realtime applications they use sharers and particles that have a black and white image (kinda like a hightmap, initially rendered separately) that determine which areas of the image should be magnified and which shouldn't. In ray tracers and path tracers, they try to simulate light a little more realistically by casting rays through an area which is "heated" or in other words has an algorithm that causes the rays to spread out or to be magnified.
ENSONIQ5 used meta balls as his heated areas and had set the properties of it to magnify the light simulating in a heated area.

Unfortunately doing this type of thing in anim8or at the moment would be either too much work, or too slow or both. Especially when there is software out there made for doing that sort of stuff (also FREE ones too!).
Title: Re: Simulate heat
Post by: Blick Fang on February 04, 2014, 03:47:38 pm
ENSONIQ5

What program did you use for that video clip?
Title: Re: Simulate heat
Post by: ENSONIQ5 on February 05, 2014, 02:16:10 am
Kreator was spot on, it was indeed done in Carrara (which includes particles and metaballs natively).  Really, neither of these things are vital to this effect, it just makes things a bit easier.  There was still a lot of frame-by-frame airbrushing to make it look less like flowing water.  Perhaps it would be possible to get a similar effect with a series or cloud of refractive spheres individually animated or perhaps motion scripted.  It would be tricky and they won't be 'blobby' like metaballs but the effect might be a reasonable starting point for later blurring frame-by-frame in Photoshop or whatever.  Anybody know if a randomiser function can be included in scripts?  This would be helpful to introduce randomness in sphere size and vector.
Title: Re: Simulate heat
Post by: TheBlackHole on February 10, 2014, 07:22:04 pm
Off topic, but:
This is why when the sun is around the horizon especially on a hot day, tends to look bigger.
That's actually an optical illusion. (http://en.wikipedia.org/wiki/Moon_illusion) When on the horizon, the sun is surrounded by smaller objects that make it look bigger by comparison.
Quote
It also gets redder because the light is weakened as it passes through more atmosphere (the light itself looses energy).
Close, but not quite. (http://en.wikipedia.org/wiki/Rayleigh_scattering) Shorter wavelengths (blue, green) are scattered more easily than longer wavelengths (red, yellow). As the light passes through more of the atmosphere, more of the shorter wavelengths have been scattered out, leaving only the longer wavelengths.
Title: Re: Simulate heat
Post by: cooldude234 on February 11, 2014, 12:43:41 am
Off topic, but:
This is why when the sun is around the horizon especially on a hot day, tends to look bigger.
That's actually an optical illusion. (http://en.wikipedia.org/wiki/Moon_illusion) When on the horizon, the sun is surrounded by smaller objects that make it look bigger by comparison.
Quote
It also gets redder because the light is weakened as it passes through more atmosphere (the light itself looses energy).
Close, but not quite. (http://en.wikipedia.org/wiki/Rayleigh_scattering) Shorter wavelengths (blue, green) are scattered more easily than longer wavelengths (red, yellow). As the light passes through more of the atmosphere, more of the shorter wavelengths have been scattered out, leaving only the longer wavelengths.

I'll agree with your second one, but I demand an internet argument on the first one. It must involve cats!