OTOY Forums

Does anyone have achieved a realistic heat distortion effect for engine exhausts? The ones I can find, using the Blender particle engine etc, later rely on composition features etc, that Blender/Octane doesn't seem to offer.

Noone? :/ I tried following the tutorials I found for Blender, but they end up using composition nodes I can't access with Octane, so I'm not quite sure how to realize this. One blender movie used a particle system, creating spheres of all sizes and colors, and then somehow used them as a controller for distortions in composition, resulting in a quite realistic heat wavering effect, that is only happening where the exhaust actually is and also usable in movie frames, progressing etc. That's somethign I'd like to achieve, but as a mere spaceship hobbyist I think I need a bit of a hint from a pro. I saw some simpler ideas, using a wavey glass plane in front of a camera etc, but that will distort the whole image and is only useful for deserts etc and not localized distortion of a jet exhaust etc.

Once you have rendered your animation out to images, you could bring those back in to Blender's compositor. Might need some render layers as well, but I don't know what techniques they used.

Indeed ... but I have run into more complications. I try to follow this tutorial:

https://cgcookie.com/blender/2014/04/03 ... s-blender/

The tutorial does something fairly complex:

1. It uses a particle system to emit spheres. Those grow with lifetime. Lifetime is random. This creates some sort of spray of spheres, that first are small, then get bigger and bigger and after a random time, die. To control the size, it uses a ramp texture, for which you need to switch to "blender render" and create the particle system texture there. It also adds a bit of random rotation of the particles. To make it more interesting, there's a turbulence force and a wind force. This works, I can switch back to octane later and it does what it should.

2. It then uses a material, where every created particle sphere has a color, that is made up of two ramped colors (once from black to red, once from black to green) and adds these together to create a mixed color *based on the rotation of the particle*... this creates all kinds of shades between the two ramp low black and the top green and red (mixed equals yellow)

3. He also uses the color to decide the amount of distortion, so old, big spheres only distort little and do not cause a sudden pop of distortion when they finally die. To achieve that, he mixes in more and more grey, depending on the age of the particle.

3. In the compositor, these colors of the spheres will decide how much distortion is applied where those spheres are located in the picture.

This then creates the heat distortion effect: the compositor warps the image only, where those spheres were and in the amount of the color of the sphere. I can put this particle emitter into a jet engine and thus create a neat distortion, that can easily be sued in a movie even, as the particle system moves along.


The problem:

- I can create a material in Blender Octane, that mixes two color gradient textures, mixes in grey etc ... but how on earth am I going to access particle system information? The nice particle info node from cycles does not do much in octane etc... ;(

This tutorials idea is great, but it seems not usable with Octane. That's a bit of a bummer, because the things he uses there, particle information, math nodes etc are all just dealing with numbers, that you could also use in Octane.

I'm not sure octane then understands, how to apply that material, though, since this is a material, that changes, depending on the particle size, position etc ... and I think Octane can only do static, single materials and not use the ingenious system he uses in the tutorial?

Finally, he uses render layers etc which has me a bit confused on how this works together with Octane. it seems to ignore the render samples override and other things.

In this case I would render the particles with Blender and try to mix in the Octane rendered frames. Basically replacing the Blender rendered stuff with the Octane rendered stuff where appropriate.