"BackLight" plugin and VRay...

[RSF]

Hello.

It seams that "backlight" plugin doens't work in VRay.

Here's an example renderes with scanline.
The green squares have "Backlight" in self illumination


I want to apply this to leaves in a tree so it must be very fast to render.
Is there an alternative in VRay?

Thanks

[Trapezium]

It works great with VRay. Starting from the left...
Standard no Backlight
Standard Backlight
Standard Backlight Filter Color
VRay w/ Refraction no Backlight
VRay w/ Refraction Backlight


http://home.comcast.net/~jonathan.re...klightTest.zip

--Jon

[RSF]

Thanks Jon.
Unfornunatly I think you're wrong
"BackLight" isn't doing anything in your scene.
In the standard material objects the light reaching the backside is just from transparency.
In the vraymaterials profected shadows are shown in the back but glossy must be used wich is a quite slow for thousands of leaves.
In the image I posted there is no ambient light just a "backlight" in the self-illumination slot. The "backlight" is just a map of the direct light that reaches the object multiplied by the respective colors used in the map settings.
Well...would be great to have something like this working in vray.
Can a similar plugin be done for Vray Vlado??
Thanks

[Trapezium]

I'm sure it works, compare leaf one and two please. The others were just me playing around.

If you want it to work with a VRayMat you should increase the output settings like I've done in the example file. If you didn't download it yet, it's offline right now but I should have it fixed by tomorrow.

--Jon

[RSF]

Hi Jon.
I really hope you're right but...
Here are the renders with "BackLight" in self illumination slot and..of course no transparency.

Rendered with scanline and raytrace shadows



and with vray (with vrayshadow since raytraced shadows don't work...should they??)



Well...I guess one can control the shadow intensity but there is no backlight to control.

If you'd like to try it:
http://clientes.netvisao.pt/ruquita/...kLightTest.rar

Thanks again

[samuel_bubat]

Hi there,

That backlight plugin does not work like used with the scanliner !
BUT !! I just did a little test and I´m very surprised !! that vray
obviously handles every material by default like a faked translucent shader.
(without seperate controls for trans color or filter color of course)
It does not seem to work with 100% opaque materials and planes without a volume.

Just do the following little test setup.

create some object for the ground. Create a thin box on top of it.
Create a direct light and place a sphere between box and light.
Place your viewpoint behind that box.

Now just assign a standard material to the box and set the opacity value
to 70. Activate Raytrace shadows and render with the scanliner.
As expected.. no shadow on the backside. Thats what the translucent shader is for (or optional the backlight plugin)

Now do the same thing with vray just set the shadow type of the direct light to vray shadows... Render again.. and there is a shadow on the backside.. Hurra.. (I allready complained this missing features in several post)

It also works with vray materials just make shure "double sided" is
turned off ! btw. double sided standard materials also don´t seem to
work. If you use the standard mat in conjunction with the translucent shader the trans btw. filtercolor take little effect with vray ,too...
just to get a little more control !
Ah yeah.. and I see it even works with shadow maps as well...
this is really cool !

well so far I just did some hybrid tests.. did´t test it with maps or anything
else
Also 100% opaque materials do not work... so still a little thing for the wishlist !

cheers

[Trapezium]

RSF, My apologies After testing your scene I see that it doesn’t work 100%. It seams that the problem lies in the VRayShadows. It does work with Shadow Maps however but I guess that defeats the purpose of using it for leaves which will most likely have opacity maps on them. I could have sworn it was working fine in the past but it may have been the transparency I was noticing.

Great tip Samuel, I wonder if this is a feature though? One thing I noticed is that it shadows the inside of the box. I wonder if this is correct. Couldn't it cause problems on curved surfaces where you may be using the opacity slot for cutting out something like a leaf.

Hmmm, This is kinda cool. If you crank up the light mult to something like 10 and turn on GI it's almost as if it's emitting light also. This is very much like translucency. Is this meant to be happening or I wonder if it's a bug?



I'll have to download the latest build and see if it works the same way.

--Jon

[ene.xis]

u can also use a vray material and use translucency

[percydaman]

for use with say 10,000 leaves, vrays translucency is not really an option.

[ene.xis]

i said "u can"....but maybe u won t
hehehe