How do I make a plane that is invisible but blocks light?

RexRed

How do I make a plane that is invisible but blocks light?

I think I bought a product a while back that does this but I forget what it was.

Any help on this is much apprecated, thanks in advance!

crosswind

Iray section plane can just do what you want.

RexRed

crosswind said:

Iray section plane can just do what you want.

Thanks Crosswind!

That clips the scene, so I cannot use it in my scene unless I can turn scene clipping off.  ...and it does not seem to clip the spotlight only mesh lights.

 

crosswind

Ah, right ~~ If so, you may use the property Iray Visible to Primary Rays on the plane... but you need to firstly add this property to the plane by using Create Advanced Iray Node Properties script in Default Resources for DAZ Studio product.

Turn off Iray Visible to Primary Rays, then you wont' see the plane when Iray preview or render, but the plane can still block any type of lights.

RexRed

crosswind said:

Ah, right ~~ If so, you may use the property Iray Visible to Primary Rays on the plane... but you need to firstly add this property to the plane by using Create Advanced Iray Node Properties script in Default Resources for DAZ Studio product.

Turn off Iray Visible to Primary Rays, then you wont' see the plane when Iray preview or render, but the plane can still block any type of lights.

Thanks for this Crosswind, but I figured it out.

Yes, you do all of the things you said, and one more thing must be set. (You missed a very important thing...)

In the surface pane, set the refraction weight of the plane to 0 to block the light and set the refraction weight to 1 to let the light pass through it.

This works perfect for my needs. This way you can block any light and then attenuate the light on the mesh to be what you need. 

crosswind

Nope ~~ I have to say that's not correct.  As what you said in OP,  if you want to hide the plane but block the lights, turning off Iray Visible to Primary Rays will just do... no need to touch settings on Surface.

But then, if you want to let the lights pass through, setting Refraction Weight to 1.0 is a wrong way as you'll get wrong lighting result. (ss1)  Because the way of setting Refraction Weight, like setting on a "new ver. ghost light" won't correctly work in your case ~~

In fact, you just need to hide the plane, as usual(ss2) ... unless you really want to have that "wrong lighting effect" in (ss1) ~~