V-Ray light and 'Directional'

[GLASS-CANVAS]

Hi Vlado,

I've noticed with the new 'Directional' spinner in a rectangular V-Ray light has an effect on a light's visibility. If I point a camera at the light and have it facing me, with 'Invisible' unticked, as I move the spinner from 0.0 to 1.0 the light object itself gets darker until it goes completely black. Bug or feature?

BTW the directional feature is great!

[simmsimaging]

Pretty sure that is the expected behaviour. As the value gets closer to 1 the light will be darker and progressively more invisible from any viewing angle that is not perfectly perpendicular to it.

[super gnu]

as i understand it the brightness of the visible light geometry varies based on the same angle as the emitted light spreads over. if you look at the light more head-on, itll be brighter. to me its not a very useful behaviour.

[simmsimaging]

Depends on the kind of lighting you need to do, but it allows you to replicate a much broader type of real world light sources (like spotlights, or boxes with light grids and/or barn doors etc.) It is very useful to me, but will be *much* more so when supported in RT

/b

[GLASS-CANVAS]

It would be nice in a future service release to have a tickbox option to make the directionality affect it's visibility or not, depending on the effect you are trying to achieve (hint hint)

[super gnu]

the directionality thing is great of course, just the "turning black when viewed from different angles" bit i dont quite get. i cant imagine a real world light source with this behaviour. sure if it was inside a recess you wouldnt see the glow from an angle, but then, it also wouldnt be black inside the recess, -and even if it was white, you still wouldnt see it if it was recessed.

dont get me wrong, im sure there are situations where it might be useful behaviour, but imho, in the majority of cases, black rectangles where the lightsources are isnt desirable.

[simmsimaging]

the directionality thing is great of course, just the "turning black when viewed from different angles" bit i dont quite get. i cant imagine a real world light source with this behaviour. sure if it was inside a recess you wouldnt see the glow from an angle, but then, it also wouldnt be black inside the recess, -and even if it was white, you still wouldnt see it if it was recessed.

dont get me wrong, im sure there are situations where it might be useful behaviour, but imho, in the majority of cases, black rectangles where the lightsources are isnt desirable.

I can see your point - but it's always about trade-offs for stuff like this, and the cheat is really about quality of light and achieving efficient use of the light rays in the CG world rather than appearance of the light (which, often enough, we don't want to see at all anyway). The trade-off for visibility is a smaller concern IMO, mainly because it's much easier and computationally cheaper to workaround, no? I'm not sure of the exact circumstances you are looking at though

/b

[voltron7]

I have noticed this too, and it's sort of annoying...I have my light looking good, but as directional passes .5 light renders black, total black...this is with a camera that is at average eyeball height of around 64" A.F.F.