Hot air

[Jambert]

Hi all,
is there a way to simulate hot air to create mirage?
thx

[StompinTom]

Yep:

- create a specular material with a slightly different IOR than air (0.9 or 1.1) and no absorption or scattering
- using ISL, modulate the density so that it's more like a cloud with no distinct edges (smoke)

The second step is the hardest part, of course, and I'm not sure how you'd go about doing that. That's how it would happen in real life, though, hot air has a different IOR than the cooler air around it therefore it refracts light differently. That, in addition to hot air moving like smoke (rising, influenced by wind, smoke dynamics), creates the shimmering, shifting mirage-like effect.

[Jambert]

The second step is the hardest part, of course, and I'm not sure how you'd go about doing that. That's how it would happen in real life, though, hot air has a different IOR than the cooler air around it therefore it refracts light differently. That, in addition to hot air moving like smoke (rising, influenced by wind, smoke dynamics), creates the shimmering, shifting mirage-like effect.

[galinette]

I'm not sure that Indigo will handle an IOR of 0.9... Negative square roots in perspective!

Aditionnally, a mirage is based on an IOR gradient, which is not actually doable in Indigo. It's maybe possible do get a similar effect, but this will be fully faked.

Etienne

[StompinTom]

I'm not sure that Indigo will handle an IOR of 0.9... Negative square roots in perspective!

Aditionnally, a mirage is based on an IOR gradient, which is not actually doable in Indigo. It's maybe possible do get a similar effect, but this will be fully faked.

Etienne

Someone who knows what he's talking about

Perhaps if volume textures were implemented, you could map an IOR range to a volume? So 'black' would be 1.0 and white 1.1...

[CTZn]

IOR is currently not mappable, niet nada... although volume textures are implemented in other circumstances.

I wouldn't refuse the option !

The way I can imagine to fake that is to use a bumped volume with a low IOR, volume that would become thinner where you want less distortion. Like a prism or a blade. The other way is to generate various fume volumes with graduated ior and stack them with the proper precedences.

I haven't tested these methods yet. Again and as Galinette said, it's all fake

[FakeShamus]

...it's all fake

ha, all rendering is fake anyway

[CTZn]

...it's all fake

ha, all rendering is fake anyway

You are right, I tend to forget this because I'm biased by the company standards

[galinette]

No, stacking IORs would not be fake, it would be a finite elements approximation of the real physics. That's a quite good idea. Otherwise, modelling curved objects by triangles would also be called fake, whereas it's also a finite elements approximation

Etienne

[CTZn]

Understood, thanks Etienne.