# "Shaping" area lights

• @seachnasaigh Thanks for this. I'll give this a try sometime this week in between projects.

• What I would like to be able to do is change the shape of an area light and have it cast light as that shape such as the aforementioned narrow rectangle.

If you think about it, this would require a shaped surface which emitted light rays in only one direction, i.e. all emitted light rays were parallel, like an infinite light. I'm not suggesting that it can't or won't be modelled - some phenomena just as unrealistic as this are!

I would use a gel and (probably) a narrow-beamed spotlight, set at a distance to make the beam less divergent, with inverse linear attenuation, or perhaps even constant. I imagine a problem with using an infinite light would be the difficulty of controlling its illumination over the whole scene.

• @chriswwd said in "Shaping" area lights:

What I would like to be able to do is change the shape of an area light and have it cast light as that shape such as the aforementioned narrow rectangle.

If you think about it, this would require a shaped surface which emitted light rays in only one direction, i.e. all emitted light rays were parallel, like an infinite light. I'm not suggesting that it can't or won't be modelled - some phenomena just as unrealistic as this are!

I would use a gel and (probably) a narrow-beamed spotlight, set at a distance to make the beam less divergent, with inverse linear attenuation, or perhaps even constant. I imagine a problem with using an infinite light would be the difficulty of controlling its illumination over the whole scene.

Your last point was one I hadn't thought of. It definitely could pose a challenge to control all that light. I imagine something like a hollow cylinder projecting light like an area light could be very difficult to figure out, and to control. But it would be pretty cool if it could be done.

I know that the main difficulty of my question is that I'm asking for something that defies physical realism in a renderer based on physical realism. Then again, we have Poser's spotlights...which from what I understand can apparently still do things that aren't strictly limited to real-world physics (like changing attenuation).

But putting it in the simplest terms, I'm only ("only", haha...!) asking for a mesh light that casts light like an area light or spotlight does.

Like you, I don't really think it's impossible, either. There must be higher-end software that can do this very thing. I just don't know what kind of amazing uber-voodoo programming magic is needed in order to make it happen in Superfly.

If it were possible, it could allow for some pretty amazing effects!

Who knows. Maybe by Poser Pro 16...?

"The difficult we do immediately. The impossible takes a little longer."

• I'm only ("only", haha...!) asking for a mesh light that casts light like an area light or spotlight does.

But I don't think you are. An area light casts light from every point on its surface in all directions (within a 180 degree arc). That won't work, because the widely diverging light rays means there won't be a defined beam of light the same shape as the mesh.

A spotlight (ignoring the snoop) emits light in all forward directions diverging from a point source (I think it's still a point source for P11 spotlights). We can control the divergence using the snoop, but the light source itself has no shape.

What I'm thinking would do the job is this: a light using a shapeable mesh (like an area light), which can emit parallel light rays (like an infinite light), but which provides some degree of control over light ray divergence (like a spotlight).

That's not asking too much, is it?

• @chriswwd Something is getting lost in translation here, I think.

Before I lost the plot and got carried away with musing on light-emitting three dimensional objects, I was originally describing this: an area light that could be shaped.

Area light:

"Shaped" area light:

I'm not sure, in the example I've given, that there would be a whole lot of difference in the overall results, but I am mostly trying to show how I would like to be able to create an object (in this case, of two dimensions) that can be shaped and emit area-light-quality light.

As regards the three dimensional object lights, I think we're getting stuck on my nomenclature, particularly my (mis)use of the term "mesh light".

If we're talking 3D light emitters, I don't want a mesh light, or mesh-light-style light.

I want a mesh object that emits light in the same way an area light does. Possibly from all its surfaces.

And by "the same way an area light does" I mean primarily light of the same quality as an area light (though producing light in 180 degrees of arc from the surface or multiple surfaces could be interesting).

All in all, I don't want the "glow" a mesh light produces, I want projected light. I'm sorry for using the term mesh light; that just confused things.

This is - to my mind, after reading your description - quite similar to what you're describing, I think. And I really like your idea of being able to control "light ray divergence".

....As an addendum it occurs to me that there were three dimensional lights in Bryce. ...I think? I haven't used it in years and can't clearly recall.

• You can already make the narrowed rectangle with the existing area light by X/Y scaling.
A black/white gobo mask would enable a lot of shapes.
Are you wanting -for example- a 2D elliptical torus like so?

I want a mesh object that emits light in the same way an area light does. Possibly from all its surfaces.

Quite some time ago, I asked for the ability to make any imported mesh an area light.I ^seem^ to recall being told that poly count becomes exponentially burdensome for the area light, thus the simple rectangle.
This would be a good point for someone more knowledgeable to confirm/deny. :D

As for projecting light, the ceiling fluorescent panels in Tink's cafe do that, and the neighborhood has streetlights which do that; you just use a high amount of ambient boost. The cost must be paid in lots of mesh light samples and lots of overall pixel samples (which means long render times), so I understand the desire for a customizable area light.

But to get the "bat signal" projected shape effect, I'd think a gobo mask would be the solution. For your streetlight example, I would simply use the elongated rectangle; light cast by a real light with that elliptical torus shape would not retain its shape on the ground 25 feet below.

• You can already make the narrowed rectangle with the existing area light by X/Y scaling.
A black/white gobo mask would enable a lot of shapes.
Are you wanting -for example- a 2D elliptical torus like so?

I want a mesh object that emits light in the same way an area light does. Possibly from all its surfaces.

Quite some time ago, I asked for the ability to make any imported mesh an area light.I ^seem^ to recall being told that poly count becomes exponentially burdensome for the area light, thus the simple rectangle.
This would be a good point for someone more knowledgeable to confirm/deny. :D

As for projecting light, the ceiling fluorescent panels in Tink's cafe do that, and the neighborhood has streetlights which do that; you just use a high amount of ambient boost. The cost must be paid in lots of mesh light samples and lots of overall pixel samples (which means long render times), so I understand the desire for a customizable area light.

But to get the "bat signal" projected shape effect, I'd think a gobo mask would be the solution. For your streetlight example, I would simply use the elongated rectangle; light cast by a real light with that elliptical torus shape would not retain its shape on the ground 25 feet below.

I hadn't considered the price to be paid in polycount. That makes sense to me, though. A faceted object projecting light from every face would be astronomical amounts of calculating.

I rather like the effect of your lights. I think they look great. But if I'm being resistant to using them it's simply for the sake of keeping my render times down.

It's likely I'll have to investigate the gobo idea.

Question: If I have a light with a gobo in front of it, and the light is facing towards the camera (not directly at it), how do I make the gobo transparent to the camera, but still have it properly act to block the light?

• I see where our paths have diverged, and it's not related to the term "mesh light", I understood what you meant there. It's related to the phrase that you emphasised in your original post: "cast light as that shape", and which I was concentrating on as your primary goal.

I assumed that what you meant by this phrase was a beam of light emitted from the object in the same shape as the object itself, so that where the light fell on a surface it provided illumination in the shape of the light emitter.

It turns out that's not what you meant at all. Sorry for the misunderstanding.

• Quite some time ago, I asked for the ability to make any imported mesh an area light.I ^seem^ to recall being told that poly count becomes exponentially burdensome for the area light, thus the simple rectangle.

I seem to remember something like this too. While messing about a while back I made a circular emitter to act as a sun substitute - used an ngon with 24 vertices and a single poly face. It was a very quick test of an idea, but certainly rendered ok. Maybe ngons would be worth experimenting with?

• @chriswwd said in "Shaping" area lights:

I see where our paths have diverged, and it's not related to the term "mesh light", I understood what you meant there. It's related to the phrase that you emphasised in your original post: "cast light as that shape", and which I was concentrating on as your primary goal.

I assumed that what you meant by this phrase was a beam of light emitted from the object in the same shape as the object itself, so that where the light fell on a surface it provided illumination in the shape of the light emitter.

It turns out that's not what you meant at all. Sorry for the misunderstanding.

No worries, and no need to be sorry. It's all good! To muddy the waters further, what you described above was indeed my original intent. A shaped light that can project its own shape -- but with your idea of being able to control the divergence/convergence of the light beams.

Upon re-reading your suggestion about the gel, I think this is likely the easiest solution for me, for now!

• You can't shape area lights, but you can make shapes out of area lights. You're limited to shapes you can make from square/rectangles, but shapes are possible. For example, 8 long thin rectangles arranged around a central axis could emulate a fluoro light. By definition, this makes area lights morphable within Poser (although the capacity isn't there yet). Lights work by calculating camera rays finding a light source; area lights are not parallel rays, they radiate from a flat plane (light is cast everywhere except above the plane). If the area light was subdivisible and morphable, you're just changing the direction of the lights 'normals', which you can do anyway by grouping individual area lights and angling them.
A few preset morphs (like tube and hemisphere) would be awesome...

• @piersyf said in "Shaping" area lights:

You can't shape area lights, but you can make shapes out of area lights. You're limited to shapes you can make from square/rectangles, but shapes are possible. For example, 8 long thin rectangles arranged around a central axis could emulate a fluoro light. By definition, this makes area lights morphable within Poser (although the capacity isn't there yet). Lights work by calculating camera rays finding a light source; area lights are not parallel rays, they radiate from a flat plane (light is cast everywhere except above the plane). If the area light was subdivisible and morphable, you're just changing the direction of the lights 'normals', which you can do anyway by grouping individual area lights and angling them.
A few preset morphs (like tube and hemisphere) would be awesome...

That's a great idea re: the fluorescent lights. I hadn't thought of approaching it that way. Once I get out from under this project I'm working on, I'll really have to do some experimenting.

• @piersyf said in "Shaping" area lights:

You can't shape area lights, but you can make shapes out of area lights. You're limited to shapes you can make from square/rectangles, but shapes are possible. For example, 8 long thin rectangles arranged around a central axis could emulate a fluoro light.

Eight area lights so arranged would work for a scene with a single streetlight, but would quickly become burdensome if making a large/complex scene. If you're going to have more than two streetlights in the scene, I would use a single area light for each streetlight.

@caisson said in "Shaping" area lights:

I seem to remember something like this too. While messing about a while back I made a circular emitter to act as a sun substitute - used an ngon with 24 vertices and a single poly face. It was a very quick test of an idea, but certainly rendered ok. Maybe ngons would be worth experimenting with?

I think yes, particularly for a sun or full moon.
One of the downsides to using the rectangular area light is that it shows in renders - both directly and in reflections. Square moons suck.
An oval n-gon emitter should do the trick for that street light, and you could have as many as you want in the scene.

• Yes it would be tedious. You'd probably also need to group them and apply a master parameter to avoid having to adjust strength on each individual light. Doesn't mean it can't be done. My preference would be for morphable area lights.
Personally I think area lights are inadequate for street lighting (although depends on the fitting). Area lights do not send light sideways, most street lights do. You get entirely the wrong side scatter from area lights in that situation.

• I meant "burdensome" in the sense of resource-heavy for the preview renderer to display the scene, and for the final renderer (Firefly or Superfly) to account for umpteen Poser lights.

What streetlight is that? It looks Stonemason-ny (a new adjective there!)

• @seachnasaigh Yes, it's definitely very Stonemasony because you're right -- it's a Stonemason piece. It's from his Urban Future set.

• I have both the Urban Future set (aka "UrbanSciFi") and the Urban Future II sets, but I don't see that streetlight. Is that streetlight maybe a separate prop from an add-on set? If it's extracted from either of those main sets, could you post a screengrab showing where it is within the set?

Who uses Stonemason's sci-fi sets? I've made Superfly adaptations of some of The Arc, Urban Future II, and Level 19 (including the add-on elevator and add-on bay doors). The Arc and Urban Future II throw multiple unreadable node connection errors in the message log. Level 19 doesn't get flagged, but the glass is obsolete and the lights don't cast light. The metal and concrete materials exceed conservation of light energy limits. It worked well for P5, but needed updated for P11 Firefly and for Superfly.

I still haven't adapted Urban Future (UrbanSciFi), Sector 15, DarkStar, Skyline Hall, Display Room, Dark Places Industrial, or the Generic SciFi Corridor construction set.
The Sky Traffic (handy for use with Dystopia) could use some headlights and taillights.

• @seachnasaigh You would be looking for his Urban Future 4 set. The streetlight is included as a prop, along with an aerial, a bollard and a couple of other greeblies.

• Oh. Didn't even know there was a 3 and 4. I don't keep up with things.

• Oh. Didn't even know there was a 3 and 4. I don't keep up with things.

Stonemason does pump out a lot of products, doesn't he? I love his stuff, and I've bought an awful lot of it, but I can't keep up either!