realistic exterior reflections

[FATdan]

i was experimenting yesterday with the output settings of a falloff map (on the reflect amount) but thats only controlling the level...i need to change the way different intensities of RGB reflect...

the closer the colour is to white the more it reflects and brighter it becomes in the reflection


the darker the colour or less light it emits the darker it appears in the reflection.

this is a real pickle. i know exactly what im after but no real solution. i suppose i could achieve this effect in PS by exporting the reflection element...

any comments or ideas would be greatly appreciated!!

[ssk]

U don't need any falloff. Just start a new Vrmtl with black diffuse color and white reflection and refraction color, turn Fresnel reflection ON. That's it.

[FATdan]

thanks for you reply ssk. I am aware that the vray mtl has the falloff included. What im really trying to achieve is changing the contrast of the reflection...not just the amount depending on viewing angle.

[CaptainObvious]

It's all about the dynamic range. Reflections are completely linear in their behaviour. If you're looking at a sheet of glass that's 10% reflective, an object with a brightness level of 100%, will have an apparent brightness level of 10%. However, the sky probably has a brightness level well above 100%, making it appear much brighter. In your example picture, the sky as seen directly is close to being white. If you looked directly at the sunset with the same expose, it would be completely blown out. However, since the glass is not really all THAT reflective, the brightness is reduced and you get that nice effect.

So, basically, if you want your trees to appear dark in reflections, and your sky to appear bright, you need to make the sky brighter and the trees darker.


Edit: Also, you need the fresnel effect on both reflectivity and transparency.

[MinaRagaie]

What im really trying to achieve is changing the contrast of the reflection...

There.. U've just said it yourself!! :)
one neat trick I've learned is to use a color correction node on a shader that's outputting reflections only and use that to change the contrast of the reflections...

Been a couple of years since I last used Max but as far as I recall...
try connecting an "Output map" to the reflection map slot and a "Raytrace map" as the input ot that...
the raytrace map will out put reflections and u can use the output map curves to change the contrast...
I've tried similar things in Maya and XSI but I never tried it before in Max

But I propably won't use such trick with Glass reflection... I'd use it with objects that don't seem reflective at all unless they R close to a very strong light source...

for Glass the The HDR method discribed by "CaptainObvious" will give u much better results.

[FATdan]

Simon- Thanks for your reply! That was a great explanation. I keep thinking about the physical aspect of what im trying to achieve but always get stuck when trying to find a solution to implement it in 3D.

Mina- Thanks again! What you described sounds exactly what im after. I intend to do some tests and explore your method.

Thanks for input people!! has anyone done any (or know of any) renders where this type of reflection is apparent? photoshoped or otherwise?

A fella called Ian Denby does some great work... http://www.idenby.co.uk/
see: images on his site

very high contrast reflections....aoughhhhhh droool.

[FATdan]

ok as promised, testers.

i might be a bit off still but im learning bits and pieces as i go. (the Golf is in progress so pls excuse the rough bits)

i attached the settings i used and a test shot. all reflective materials have the same output on the environment slot.

Thoughts, suggestions, crits ????

Thanks

[mister3d]

Do you want to use 2 different reflections for a falloff? What kind of brightness changes do you want for each?

[FATdan]

im trying to avhieve reflections where objects that dont emit light are dark and the sky is very intense. The sky part is easy. Its making the other stuff actualy appear dark that im finding hard...

[playmesumch00ns]

Just make the sky loads brighter, then when you expose to compensate all the other reflections will get darker. You're trying to replicate en effect of realstic lighting that's very easy to achieve if your lighting is realistic. You'll have to rejig your scene and your shaders a little but it'll be worth it. It'll also help if you use linear lighting, i.e. view your renders with a gamma appropriate for your monitor (probably 2.2).

In raw outdoor situations the lit side of an object can often be 20-50 times brighter than the fill side. It's those contrast differences that you're trying to achieve. Remember that the sky is basically a massive, super-bright area light.

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