How to simulate terrain fading in the distance?

[Morne]

Hi all

I recently had a problem with a terrain of about 200km X 200km. My scene units and display units was setup to mm as I always think in mm and I needed to move things in small increments over the terrain. My textures was huge to cover the terrain. But now in real life even on a good day you can't see that far. I reckon you can see about 100km far and then everything like mountains etc fades to blue anycase in the distance. How can I simulate this by flying over my terrain, the closer things get the less "blue" they are and the further they get the more "blue" they get?

I was thinking of doing this with fog, but haven't used fog since max 2 and worried that VRay will take forever to calculate and render this.

Any suggestions will be appreciated.

Kind Regards,
Morne

[re:FORM]

Fog renders pretty fast as long as you don't add noise... which I doubt you need for the effect you want. Alternatively stick your ground texturemap into a mix-map along with a blue-ed version of the same map, and use a falloff map in the mix slot with falloff set to distance from camera. You should be able to set the distance that map blends to its blue version.

[Morne]

Thanks re:FORM, but I was thinking more in the lines of the scene "fading away". So probably fog will be my friend. The distnace from camera thing sounds interesting even though I probably wont use it here, maybe for another situation.
Anybody else vote to use fog in this situation?

[re:FORM]

The other option is to render a z-depth pass and then comp that in post overlayed on your normal render. You should have more control that way and you can use the z-depth pass to add some subtle dof to soften your horizon.