Live Action & CG for VRay Tutorial

[Infrared digital]

This is great info John many thanks.

Finding grey spheres/probes isn't easy. I have tried looking for 18% grey car primer, which isn't easy to find also. I would have thought that the VFX industry somewhere in the world would have these things as standard !! A MacBeth chart is £70 !

Is there a list of render elements that you render out as standard ?

[joconnell]

You're quite right and that is a bit strange that there isn't an "official" grey ball. What most folks do is get a calibrated chart (which I agree is fucking pricey) and then get any local paint shop to match the 50% grey sample in a matte paint. Buy yourself a mirror ball at a garden center, prime one half of it and then use your calibrated paint on top. It won't be totally bang on since the paint will have a tiny bit of specular itself but it's going to be pretty close.

Pass wise we stick out a huge amount of them for the compers in here so it largely depends on what level of depth you want to go to. The main thing is if you want to be able to grade the light and gi without affecting the colour of your object which adds in the extra layer of complexity.

If you want to go simple then:

VrayGlobalIllumination (only your bounce)
Vraylighting (only your direct)
Vray Reflection
Vray Refraction
Vray Specular

And if necessary:

Vray self illumination
Vray sss2

So you pretty much just add all those on top of each other to make your beauty.

If you want to be able to change the colour of your light hitting your objects without affecting the colour of the maps that are in it then you've to start using the raw passes:

Vray diffuse Filter
Vray Raw Global illumination
Vray Raw lighting

Each of the above get first multiplied by your diffuse filter to make the global illumination and lighting passes and then you go into your reflection / spec and so on.

[Infrared digital]

Hi John

I appreciate your time but render elements is something that I have struggled with over the years.

Am I being naïve in thinking that when all these render elements are stacked up in photoshop or After effects with all the blending modes set correctly that they will match the RGB render from VRay ?

[joconnell]

That's the theory alright but often there's a tiny bit of a difference - for one thing the vray raw reflection and reflection filter passes don't work correctly. In theory the two should multiply together to make what came out as the vray reflection pass but they don't work correctly. The chaos guys have changed this internally so that it does work as expected but a lot of it also depends on how your compositing package treats colour and blending internally. You have to stick to nothing but vray shaders to get the correct information out from the passes, but there might still be a tiny amount of difference. I've found it's mainly the reflections that break it, so likely the refractions too.