Determining correct falloff

[viscorbel]

Haha! awesome man
Now we can use the osl in both falloff slots and have a linear result. Thanks!

So problem solved Grant, just need to use this little osl for correcting all your reflection maps

Yes, that does it:

facing_ratio_linear.osl

shader facing_ratio_linear (
       output color Col_Out = color(0.5)
)
{
       float floatOut = acos (1.0 - (1 - (dot(normalize(N), normalize(I))* -1)))/(M_PI * 0.5);
       Col_Out = color(floatOut  , floatOut , floatOut );
}

Thanks Vlado!

[Wobi]

Haha! awesome man
Now we can use the osl in both falloff slots and have a linear result. Thanks!

In fact, you don't even need to use a falloff map anymore. You can just use an output map to alter the curve, since this should be a little bit more effective for computation, I guess.

[vlado]

Yes, if you can recreate the same curve with an Output map, it's probably going to be somewhat more efficient than the OSL shader (there's some overhead involved with OSL, even if the shader is just one line).

Best regards,
Vlado

[Vizioen]

Now, could someone also show the difference this has on a material? Just curious to know if this was all worth it

[DanielBrew]

Now, could someone also show the difference this has on a material? Just curious to know if this was all worth it

It was worth it!

[jackieteh]

Yes, that does it:

facing_ratio_linear.osl

shader facing_ratio_linear (
       output color Col_Out = color(0.5)
)
{
       float floatOut = acos (1.0 - (1 - (dot(normalize(N), normalize(I))* -1)))/(M_PI * 0.5);
       Col_Out = color(floatOut  , floatOut , floatOut );
}

Thanks Vlado!

I am vray 2.40 user, how can use the file?

[theedge]

I am vray 2.40 user, how can use the file?

As mentioned earlier it turns out that you can just as well use an Output map so don't worry about that OSL shader.

[Wobi]

Yes, if you can recreate the same curve with an Output map, it's probably going to be somewhat more efficient than the OSL shader (there's some overhead involved with OSL, even if the shader is just one line).

What I originally meant is that you don't need to put the OSL-Shader into a falloff map, but you can just use an output map with the OSL-Shader put into it. Since the output-map does less calculation then the falloff-map.

As mentioned earlier it turns out that you can just as well use an Output map so don't worry about that OSL shader.

Of course you can use an output map, but this will be not as precise as the OSL-Shader, since this will give you just an "eyeballed" curve and not a mathematically correct curve...

[viscorbel]

Plugging it into both slots of the falloff would make it quick and easy to convert old materials, where some folks have spent hours trying to match those pesky reflection curves

When making new materials, it does make more sense to run the osl through the Output map.

[Dave_Wortley]

I'd say the difference between the eye-balled Output curve and the OSL curve would be so negligible as to not warrant the extra slow-down from OSL.

Thanks for bringing this up. Very very interesting, we've used Falloff maps in ExtraTex render elements and used them in comp to mask things and we've notice oddities that we were thought to some weird gamma issue. This makes a lot more sense all of a sudden.

I've reported this to heading of rendering engineering at Autodesk and it surprised him as well.

[theedge]

What I originally meant is that you don't need to put the OSL-Shader into a falloff map, but you can just use an output map with the OSL-Shader put into it. Since the output-map does less calculation then the falloff-map.

Ok, I misunderstood the original post. Sorry.
How would the final material setup look then when using the shader in an output map ?

[Wobi]

That should be something like this:

OSL-Texture -> Output-Map -> Reflection-Color of VRay-Material

Since the OSL-Shader is like a Falloff-Map, just with a linear Falloff, there is no need to plug this into a Falloff-Map again. Of course, as Viscorbel mentioned, it makes sense when updating old materials which already have a custom curve in the Falloff-Map.

Cheers,
Ben

[samuel_bubat]

It would be pretty cool to have enhanced curves wihtin the VrayHDR Loader. So that you could save and load curves from a preset file
as well as script access (without the need to animate them in the first place).

[Dave_Wortley]

It would be pretty cool to have enhanced curves wihtin the VrayHDR Loader. So that you could save and load curves from a preset file
as well as script access (without the need to animate them in the first place).

+1 for a VRayOutputMap with better animation controls.

Technically the VRayLut or VrayICC already does this if someone wants to make a LUT to convert a Falloff to a linear Falloff.

[dubcat]

Is this OSL only for reflection or should we use it on the Gloss Falloff as well ?


Using the falloff from the toycar in episode 04.