I've created an aircraft engine and would like to create an area behind it that
is distorted due to the heat from the exhaust. What's a good way of achieving
this?

-Mike

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"SharkD" <nomail@nomail> wrote in message 
news:web.4950dc7b2d61d8ce4a212ac50@news.povray.org...
> I've created an aircraft engine and would like to create an area behind it 
> that
> is distorted due to the heat from the exhaust. What's a good way of 
> achieving
> this?

waves/ripples patterned density map applied to scattering media? .... almost 
completely transparent. between the camera and object to distort the view. I 
also just recalled that you may be able to apply a distortion to the camera, 
not 100% sure! The former idea seems like it would be a localized effect, 
while the later would have a gloabal effect. Hope that gets some ideas 
flowing .....

Jim

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SharkD wrote:

> I've created an aircraft engine and would like to create an area behind it that
> is distorted due to the heat from the exhaust. What's a good way of achieving
> this?

Maybe try adding random transparent spheres with varying ior.

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"SharkD" <nomail@nomail> wrote:
> I've created an aircraft engine and would like to create an area behind it that
> is distorted due to the heat from the exhaust. What's a good way of achieving
> this?
>
> -Mike

That's a tricky one.

A naive attempt would be to create a transparent cylinder or cone with a
slightly different ior and a disturbed normal. But then you'd get total
reflections at the outline of that object, which will be a mess if the surface
is turbulent enough to be noticeable at all.

An approach I did was to put a plane (no, not the aircraft :)) parallel to the
"screen", using a slightly different IOR for the "rear" side, and setting up a
function to be turbulent only in those areas where the exhaust should be
visible.

Drawback with this one, though, was that I found it to create artifacts when
combined with media, which you may possibly want to use for some engine smoke.

So if you find some solution that really works, please by all means post it here
:)

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Jim Holsenback nous illumina en ce 2008-12-23 08:32 -->
> "SharkD" <nomail@nomail> wrote in message 
> news:web.4950dc7b2d61d8ce4a212ac50@news.povray.org...
>> I've created an aircraft engine and would like to create an area behind it 
>> that
>> is distorted due to the heat from the exhaust. What's a good way of 
>> achieving
>> this?
> 
> waves/ripples patterned density map applied to scattering media? .... almost 
> completely transparent. between the camera and object to distort the view. I 
> also just recalled that you may be able to apply a distortion to the camera, 
> not 100% sure! The former idea seems like it would be a localized effect, 
> while the later would have a gloabal effect. Hope that gets some ideas 
> flowing .....
> 
> Jim 
> 
> 
A media won't distort anything.
A distortion applied to the camera will tent to affect the whole scene. It you 
manage to restrict it to a given location, you'll have to change it if you 
change anything. It won't work if there is anything between the camera the the 
parts that you want perturbed.
Some emissive media can be used to make the flame of the exaust visible.

My take would be to place a long cylinder or a cone with pigment rgbt 1 give it 
an ior around 0.99 and use a slight normal perturbation: normal{bozo 0.1 
scale<100,1,1>} for a jet along the x axis. Rotate as needed.

-- 
Alain
-------------------------------------------------
Don't waste your time on a man/woman, who isn't willing to waste their time on you.

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clipka nous illumina en ce 2008-12-23 13:52 -->
> "SharkD" <nomail@nomail> wrote:
>> I've created an aircraft engine and would like to create an area behind it that
>> is distorted due to the heat from the exhaust. What's a good way of achieving
>> this?
>>
>> -Mike
> 
> That's a tricky one.
> 
> A naive attempt would be to create a transparent cylinder or cone with a
> slightly different ior and a disturbed normal. But then you'd get total
> reflections at the outline of that object, which will be a mess if the surface
> is turbulent enough to be noticeable at all.
With an ior just very slightly less than 1, as the heated air should be, that 
effect will only affect a very narrow area and may not be noticeable.
You can use 2 cylinders or cones, or a cylinder and a cone. The outer one get an 
ior around 0.999 and the inner one about ior 0.99.
You can also flatten those: scale<0.5,1,0.5>. This will make the areas where the 
problem may occurs even smaller.
> 
> An approach I did was to put a plane (no, not the aircraft :)) parallel to the
> "screen", using a slightly different IOR for the "rear" side, and setting up a
> function to be turbulent only in those areas where the exhaust should be
> visible.
> 
> Drawback with this one, though, was that I found it to create artifacts when
> combined with media, which you may possibly want to use for some engine smoke.
> 
> So if you find some solution that really works, please by all means post it here
> :)
> 
> 
> 


-- 
Alain
-------------------------------------------------
   I knew a girl so ugly that she was known as a two-bagger. That's When you put 
a bag over your head in case the bag over her head comes Off.
	Rodney Dangerfield

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Alain <ele### [at] netscapenet> wrote:
> Jim Holsenback nous illumina en ce 2008-12-23 08:32 -->
> > waves/ripples patterned density map applied to scattering media? ....
>
> A media won't distort anything.

Hah! Jim's idea is not so stupid after all; you're only correct as long as you
use "standard" Type 1 (isotropic) scattering. But if you use Type 2 (Mie haze)
or, probably better yet, Type 3 (Mie murky) scattering, this might actually get
you somewhere...

It's definitely not an exact model of what is really happening with hot air, but
still it's definitely worth a try.

> My take would be to place a long cylinder or a cone with pigment rgbt 1 give it
> an ior around 0.99 and use a slight normal perturbation: normal{bozo 0.1
> scale<100,1,1>} for a jet along the x axis. Rotate as needed.

Tried that. My experience is that if you pertube it strongly enough to get any
noticeable effect, you get ugly outlines due to total reflections.

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Christian Froeschlin <chr### [at] chrfrde> wrote:
> SharkD wrote:
>
> > I've created an aircraft engine and would like to create an area behind it that
> > is distorted due to the heat from the exhaust. What's a good way of achieving
> > this?
>
> Maybe try adding random transparent spheres with varying ior.

That sounds like a good idea. I tried nesting a series of cones, but it didn't
look so hot.

-Mike

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"Alain" <ele### [at] netscapenet> wrote in message 
news:49513fe9$1@news.povray.org...
> My take would be to place a long cylinder or a cone with pigment rgbt 1 
> give it an ior around 0.99 and use a slight normal perturbation: 
> normal{bozo 0.1 scale<100,1,1>} for a jet along the x axis. Rotate as 
> needed.

Expanding on the cone idea .... rib the cone with tori. Afterburning engines 
gable the exhaust nozzle from cylinder to cone-ish shape, and the exhaust 
plume has these bright rings along it's length.

Jim

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"Jim Holsenback" <jho### [at] hotmailcom> wrote in message 
news:49521f4f@news.povray.org...
>
> "Alain" <ele### [at] netscapenet> wrote in message 
> news:49513fe9$1@news.povray.org...
>> My take would be to place a long cylinder or a cone with pigment rgbt 1 
>> give it an ior around 0.99 and use a slight normal perturbation: 
>> normal{bozo 0.1 scale<100,1,1>} for a jet along the x axis. Rotate as 
>> needed.
>
> Expanding on the cone idea .... rib the cone with tori. Afterburning 
> engines gable the exhaust nozzle from cylinder to cone-ish shape, and the 
> exhaust

      ^----------
meant to say gimble

> plume has these bright rings along it's length.

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