Why is a light not like a light?

Simple question. The lights in blender, why are they in Quadratics Energy and all manors of logical terms instead of things like every day lights like watts 65watts 75 so on . Their are lots of different lights as well each with different outputs

its easier to understand, and customize settings in numbers. No one wants to try and figure out how many watts it takes to light up their scene

you sure? Lamps still dont have a 3d display off their distance You kinda just toy with it. And even if a spot light has a disstance that does not reach a mesh it still gets light

yeah, thats to create a more realistic fall-off.
And lamps actually can have a 3d display of their distance. its the sphere setting. Then you can get great control of the distance it reaches. if you dont have it on, its just a light, that goes onfor slightly more than the distance(to get that fall-off effect)

I think the reason is because the light isn’t measured in watts, electricity is.

Light is measured in something else. And other reasons like how the sun doesn’t have watts.

Eh, but energy slider makes no sence already.
Logicly a light has to have a source, and if that source is in front of a camera there should be a solid dot of light right there not the underlining scene

And a sphere of light with a fall off should have a path of light to the source

no, because that would only be in one direction. And light is not a physical thing. Especially in CG. Its calculations, not objects.

a lamp is in all directions
And if I want to set up lights naturaly it would be nice if they behaved like nature

well since Blender has no units (measurement units) then a lumins or watts setting would be innapropriate.


Watts is the unit for Power.

Power = Energy / Time

We’re not seeing how much power the light can produce but how much energy it outputs.

More energy = more intense right?

Play around with a magnifying glass and you’ll see what I mean - the light (a form of energy i.e. solar) gets concentrated at one point beneath the lens of a magnifying glass and becomes brighter/more intense.

If you want a term it would probably be in Lumens, or candlepower, the watts of a light vary from what type of lamp it is(florecent, incandecent). but i think another thing is scale, not every scene is scaled exactly the same so the energy required to light on scene would be different from one to another.
If you want naturely acting light you’d have to use indigo or yafray, cause light doesnt just hit a surface and stop, it hits a surface and bounces off in all directions, diffusing its energy each time. So its a sacrifice speed for accuracy, blender internal can give good faked lighting, pretty fast. but realism takes alot computation, and alot longer to render

Drat… well that explains a lot

I just started playing with Indigo. It takes a lot longer, but I think the physically accurate lighting is worth it.:slight_smile: I’ll post an example render tommorow when it’s finished…

If you want to see a light, you have to create the bulb; put a sphere of glass around a lamp and then you will be able to see it. Technically, youngbobcat, you don’t see light, you see the reflection of light from something, or the emission of light (see the emit button).

Alltaken, you are correct; if there are no units, there can be no unit standards.

Besides, what good would it do? You would add a 60 watt bulb to your scene, and then, if it wasnt enuf, you would increase it to 90 or 100. Same is true for energy units.

What I would love is for an option to show the lux of a given point. THAT would make blender SO usefull. You can imagine how amazing that would be for the engineering industry. At the moment, the only system that renders a fully realistic scene and gives you accurate Lux readings costs $25k. Not cheap.

but i think another thing is scale

Absolutely! Imagine trying to light a scene with a sun! You’d have to crank the energy up to a few billion lumens (wild guess) then find a computer on the opposite side of the world to position the damned thing.

As I recall (@ndy and Matt discussed this on the conference video) the “Distance” setting represents the distance at which the energy is half the initial energy. From here it presumbly halves again for each subsequent measure of the distance setting.

Well there are Blender units, but I never learned them :stuck_out_tongue:

As for a scene with light bulbs… one 60 watt makes a room dim, a few more even it up quite nice. It would work as it does in reality.

As for the sun. Thats what stuff like GI is for is it not? That way you dont have an object, instead you have a date location and time to place where is

things like area are actually light boxes and barn doors

GI isnt just from sun light, GI is what is created from light bouncing around, it is the same thing as radiosity. Light bouncing off surfaces indirectly illumanating objects not in line of sight. GI is mostly comonly used for atmospheric lighting(air also reflects light) Blenders AO fakes this once again with tricks, but it isnt technically correct.

Um… I may be incorrect, but in terms of physics, quadratics are an accurate means of expressing light in numbers. They’re used quite frequently by people and other software.

Further, if you want light that’s accurately depicted as a film or television lighting designer would, then you would express the light by its temperature in Kelvins.

For me, these numbers work just fine.