Control points for rectangular light / trapezoidal light

It would be really helpful to be able to adjust the corners of a rectangular light independently. Obviously (I think?!), constrained to a flat plane, but it would be good to be able to pick up one corner and shift it so that the light is trapezoidal or even close to being triangular.

Another option would be triangular lights?

Maybe there is a work around to achieve this with the current tools?


Rectangular lights can’t be made trapezoidal but if you are using the Raytraced viewport… you can use the command TestShowPrivateContent to expose the Cycles Emissive material which is still being developed for Rhino. This material type will then be found in the more types section when making a new material and can be applied to any object. Make sure to uncheck the ‘hide’ option in the emissive material if you want to see it. I tend to also prefer a combination of real lights like rectangular and objects with emissive mats. If you try to do all the lighting with emissives it can be slow to get a clean image.

Thanks, that could be helpful.

I’m not absolutely clear from your answer if you are saying it isn’t possible currently (which I know) or if it is not ever possible via creation of a new light (which I don’t know)?

Will give the emissive surface a go, would it work like a ‘portal’ light for encouraging light through a window? I’m trying to do that with a triangular window currently, hence the request. Maybe such hacks aren’t needed with the Cycles render? It’s something I’ve got into the habit of doing over the years and maybe isn’t needed anymore?

To my knowledge you cannot change the shape of a rectangular light but some apps (not Rhino) can allow for changing the light type to impact shadows for instance, this is still not what you are asking about though in terms of a trapezoidal shape change. If you are using the Raytraced mode which is Cycles or the Rhino Render Next project which is also Cycles, you could try increasing the number of diffuse bounces in the Cycles options within Rhino Options too. An emissive material will not act like a light portal which you may be use to from other renderers.

Currently I’m using rectangular lights as I would have used ‘portals’ in other renderers. Maybe that’s completely ineffectual. I’ll try doing without but what I have normally found is that insufficient light makes it inside a building.

But, I’ve just been doing it out of habit with cycles and don’t actually know if it necessary or beneficial.

Still, it would be interesting to have a triangular light type, incidentally, a circular one would be good too. A feature request.

You can use a Point light or a Spot there now. For the triangular shape, if that is the window opening profile, I’d also try any light type outside the window pointing inward. Without seeing a model or renders it’s a guess but that should give you the profile you want in the shadow.

That won’t work in all cases sadly, it’s also about illuminating the inside so that you can see it properly from outside. Having a strong point or spot light positioned in such a way as to achieve that would look crazy externally.

Rectangular lights work perfectly for 99% of cases. I just position them just outside there glass of the window and they then don’t seem to unduly illuminate the frame but they do (tbc with cycles) help illuminate the interior.

The odd time they don’t work is when the window shape is unusual AND the window is positioned very close to the plane of the exterior wall, or some situation where the window has no enclosing wall. I can send a screen shot showing the problem situation tomorrow