refraction fog color range seems to be clamped.

[dust1n]

vray build: vray_adv_22001_maya2012_x64

walking around the color wheel trying to get orange in my fog color... but it will only render red or yellow. the same goes for other color ranges. this is with diffuse, reflection and refraction colors at white.

this is for a headlight assembly lens. i can get an orange result altering diffuse and reflection... but if i throw a clear lens on top it knocks the reflection color down and goes back to looking yellow.

is this an issue... or am i doing something wrong?

[vlado]

You could try to adjust the fog multiplier as well (I guess you will have to increase it a bit to make glass less transparent).

Best regards,
Vlado

[joconnell]

Fog in vray for max can be very delicate in terms of it's units and the fog colour so if you're getting a very intense result you may want to look at the size of the geometry that vray is tracing through from the front out to the back and see how many maya units it needs to go through. In max for example, vray's material will give you the fog colour you choose if your object is one centimetre deep in terms of how far a ray needs to travel to pass through the object. It also assumes that you've got a full refractive object and it's against a white background. If these three parameters are correct then you should get your fog colour back fairly precisely. If the object is less refractive, then you'll get less of your fog colour. If it's on a non white background, the background refracted through will tint your fog colour's effect. Most importantly though, if your object is more than a single scene unit deep (I'm not sure what maya uses by default) then the fog multiplier will have a large effect. From the sounds of your fog effect being too intense, I'd say your mesh object is way deeper than one scene unit so what you need to do is found out how much deeper, then divide the fog multiplier in the material by that value.

Say for example in max I'm using centimetres as my units, and I have a cube that's 10 cm in every direction. For a ray to go through to the other side, it has to travel ten cm in this case. With the vray material, the fog assumes that my object is only one cm deep so my object will look intense. What I need to do is take the depth of my object (10cm) and divide my vray fog multiplier by that value, so 1.0cm (fog mult) / 10cm (obj depth) = a multiplier of 0.1 - this reduces the intensity or build up of the fog effect to a tenth of it's previous value. Likewise if your object is 100cm deep, then 1.0 / 100 = a multiplier of 0.01. Vray recently changed to allow system units to have a bearing on the fog settings so it'd more easily adapt to different scenes, but for a start try reducing your fog mult by a factor of 10, then 100, and so on.

[joconnell]

Or just read Vlado's more succinct answer

Vlado - the fog system units scaling tick box in the max material, does this just mean that vray will convert from it's internal cm to whatever the equivalent is in scene units or is it using the object bounding box as it's guide instead?