Does the light multiplier work for a light portal also?

[m_haertel]

I had a crazy night! Actually I just wanted to bring more light into a architectural scheme. (basically a opaque roof with glazed facades around)Even considering all the gamma issues, interior views will show an almost black ceiling. Previously I try to compensate this a little bit by using high multipliers for white materials but since Micha told us about maximum white code 205,205,205 there seem to be other ways, aren't there? So of course I set rectangular lights in front of all the facades now. BUT I do not like the fact that the very edge of the ceiling is sort of glowing now. (I think it should be almost the darkest point. (At least simple GI calculations show the edge and the very inner parts of the ceiling as darker.)

Since I use a HDRI Environment I now tried to change the rectangular lights into light portals and can not adjust the brightness anymore. It is too dark again and there seems to be no way to make the portals more efficient.
My settings are about those:
-light sources: GI-environment 1 or/and directional light 10 (alternatively a very bright HDRI with multiplier 0.01) settings for photon/caustic subdivs are on their defaults 500/1000; I have no idea what light multipliers are common, I just judge it on my gamma corrected textures. If they turn to be too bright already the space under the floating roof is still dark grey.
-light portal: On/Multiplier 0.001..200/no decay/subdiv 8/photon 500/caustic 1000/shadows enabled bias 0
( ??? Why does it not work with decay? What is the idea behind "ignore Light Normals?"- it makes no difference to my scheme.)

That I can not get any better light from the portals is very strange because when I did some test with a little "box" before it seemed to work fine. Multiplier .0001 was just showing some effect, 200 would be too bright, something in between was good and worked with plain environmental light, directional (sun-)light and also with my HDRI. Suddenly the multiplier does not work anymore. There is just one standard effect: light portal on or off. I start to think that the previously working option was just a dream, because it was very late and even in my little test box i can not get the multiplier back.
So, IS IT WORTH TO TRY AGAIN? or is the multiplier really a "dead" function for portals? In that case, how to brighten my room up without burning the environment into a dessert? :
MatthiasH


p.s.:
For me as a beginner this simple scheme is an incredibly complex situation already. GI depends on so many settings: light intensity, material reflection, possibly also the render settings. I feel like in front of a huge audio mixer. Since I can not trust any of my own settings (no experience!), I am usually afraid of making everything worse. (by the way, thank you very much Micha for the "allround settings"! this is at least one thing for now I do not worry so much about anymore.)

[Micha_cg]

Re: Does the light multiplier work for a light portal also?

The light portal is dependent from the GI env intensity only. Increase the GI env intensity and you get waht you want. Place the lightportal inside could help lower render times, but I'm not sure. For window glass I would enable the material option "affect shadow", so no caustics are calculated. Maybe, in this case is dosn't matter where you place the light portal. But try to avoid to place two objects at the same place: light port and window surfaces should get an offset.
Sometimes, if objects are sharing the same place, it helps to set the global option bias at 0.001 or something small. There was an example at the old user tutorials, that I can not find anymore. I think it will be upload again in the next time.

[joe_b]

Re: Does the light multiplier work for a light portal also?

http://www.spot3d.com is home to the V-Ray for 3dsmax docs and can be a useful resource for parameter descriptions since most of them are common to VfR as well.

[*]Double-sided - when the light is a planar light source this option controls whether light is beamed from both sides of the plane. This field has no effect for spherical light sources. [*]Invisible - this setting controls whether the shape of the VRayLight source is visible in the render result. When this option is turned off the source is rendered in the current light color. Otherwise it is not visible in the scene. Note that this option only affects the visibility of the light when seen directly by the camera or through refractions. The visibility of the light with respect to reflections is controlled by the Affect specular option.[*]Ignore light normals - normally, the surface of the source emits light equally in all directions. When this option is off, more light is emitted in the direction of the source surface normal.[*]No decay - normally the light intensity is inversely proportional to the square of the distance from the light (surfaces that are farther from the light are darker than surfaces which are closer to the light). When this option is on the intensity will not decay with distance.[*]Skylight portal - when this option is on, the Color and Multiplier parameters are ignored, instead the light will take its intensity from the environment behind it.[*]Store with irradiance map - when this option is on and GI calculation is set to Irradiance map V-Ray will calculate the effects of the VRayLight and store them in the irradiance map. The result is that the irradiance map is computed more slowly but the rendering takes less time. You can also save the irradiance map and reuse it later. [*]Subdivs - this value controls the number of samples V-Ray takes to compute lighting. Lower values mean more noisy results, but will render faster. Higher values produce smoother results but take more time. Note that the actual number of samples also depends on the rQMC Sampler settings.[*]Shadow bias - bias moves the shadow toward or away from the shadow-casting object (or objects). If the Bias value is too low, shadows can "leak" through places they shouldn't, produce moire patterns or making out-of-place dark areas on meshes. If Bias is too high, shadows can "detach" from an object. If the Bias value is too extreme in either direction, shadows might not be rendered at all.