we still like vray

[studioDIM]

duh i get it.
As skylights portals are lightfixtures the sampler looks that way.
black envirnoment means they won't light, but lo! the lightmaterial behind will be somehow close

Another lesson in "using the tools you have knowingly"

Thanks.

[ene.xis]

(*) I used light portals around the bulb to tell v-ray where to look for the light source.

ok, but how do u use light portals around the bulb?

[studioDIM]

just place 5 plane area lights around the bulb, and set them to skylight portals.




Lele

[ene.xis]

hum...
i was hoping for a less elaborated solution...

[Clifton Santiago]

I still don't get it. Could you elaborate more?

[DaForce]

YOu just need to put a certain number of vray lights around the light bulb facing outwards.. and then tick skylight portal on each one.
Kinda of tall thing vray lights the height of the bulb and wide enough as to not have any gaps between it and the next light.

[studioDIM]

sure.
I *THINK* light fixtures receive special attention during the pathtracing/GI phases (after all they surely emit light, whereas normal pixels receive it and bounce off a little).
In the case of the cornell box, we have a LightMaterial, incapable of casting direct light, which is applied on a piece of geometry, of some shape, somewhere within the scene.
There are no light fixtures at all, and i can see why the light distribution might take more time: lights are GI only lights, and the location and extension of these is fairly unknown.
Putting lights at the faces of the bounding box of the lightmaterial object (5 out of six in the case of the emitter) will ensure that the area around the light fixtures gets a special attention, making the lighttracing somewhat faster, as it goes towards the lights to see what they emit (nothing in our case) and finds thereabout the light emitting material.
IF i ain't raving (as per usual) this is just a clever aid to lower rendertimes under these conditions.
Normally, one would have light fixtures in a scene, so the issue wouldn't be so relevant.

I can hear something cracking...
Maybe a rock is letting go somewhere near me :P

Lele

[Clifton Santiago]

Okay, so the planar vray skylight portal lights enhance the directionality of the bulb which is an object with a vraylightmat assigned to it. But why do they need to be skylight portals? Why not just be instanced regular vray planar lights? Or conversely, to make the bulb cast more light, why not turn up the vraylightmat multiplier? or the object send GI value?

[studioDIM]

But why do they need to be skylight portals? Why not just be instanced regular vray planar lights?

As the goal is not to cahnge the original lighting setup of the scene.
We still use the object Lightmaterial to light, this way, but help the tracer find it faster.

Or conversely, to make the bulb cast more light, why not turn up the vraylightmat multiplier? or the object send GI value?

For the same reason as above, the lighting value is right already.
We just help vray know where to look.

Again, it IS a guess.
Also, it might help wiht cleaniness, but not with time, or the other way around. i haven't tested it yet.

Lele

[studioDIM]

Ok, i have done some tests, and i have to say WAO.
The cornell scene above has the LC take a fair bit longer (say roughly 4X), with the same settings withough the lightportals, but it samples a LOT better.
Straight away sampling goes where it's needed, and when the AA/QMC pass kicks in, it has apparently a LOT less work to do to get the image clean.
Probably the amount of subdivs for the LC can be lowered a lot to get back roughly in the same time-frame as the standard setup one.
I'd rather not post images nor timings, as the silly pc i am working on is dead slow, but by all means, people, do give it a try.
Amazing how a simple thing can change the behaviour of the LC.
I'm really impressed.

Lele

[studioDIM]

Tested it, and DOH!



3000 subdivs (9M samples), 7:18, no lightportals.



1000 subdivs (1M samples), 4:22, lightportals.

Maxwell was JUST a physicist.
Let him rest in peace.

Oh.
Times are one SINGLE athlonXP (32 bit) 2000Mxz, 1Gb ram.
VRay's of course 1.47.03.

Duh-Lele

[studioDIM]

replying to meself now, but the chain of thought's is quite mad right now.
It means i can have coloured vraylight materials on objects, with a vraylight enclosure which will be as fast to trace in GI as standard vraylights.

And i wanted gobo vraylights, right.

I keep saying: give Me the same chisel and hammer and marble as Michelangelo, and i will NEVER create a David.

I have now something to play with waiting for 1.5...


Lele

[jonnybefree]

but you have a nice veggi garden to play with too i think

nice tests tho

[Da_elf]

can you show us a screen cap of your light setup?

[studioDIM]

Lele