I’d never heard of measuring it with Kelvins… but there’s a lot I haven’t heard of.
the “Distance” setting represents the distance at which the energy is half the initial energy.
Ah… Speaking of lightbulbs, one just went on over my head. Thanks for this!
Well there are Blender units, but I never learned them
There’s nothing to learn, they’re just squares on your screen. They have no relation to any actual measurement units of physical things, which is why they’re useless for calculating things like light (in real unit terms).
My mistake… I was talking more in terms of color temperature than in terms of intensity. That’s what I get for jumping into a conversation before my brain’s wrapped itself properly around the topic at hand.
This isn’t a direct answer to your question, but I have to highly recommend this book:
This is a really good book on, well, digital lighting and rendering which will really help you make the leap between real life lighting and digital lighting. The short answer is that they are similar and they are also very different. Also, Blender’s lighting system is very much like the lighting systems in pretty much all 3D apps, so your questions aren’t Blender specific.
As for your specific question, I think that you would probably not bounce a spot off of a surface to get diffuse light in a digital scene. You could, using raytracing and radiosity, but this would be a very computationally expensive way to do it. Probably you would simply use a diffuse light source. Depending on what you want there are area lights, hemi lights, and spots with soft edges, no shadows, and/or specularity turned off, which can all result in various kinds of diffuse light.
These kinds of things, “turning off” specularity and shadows, etc, are the kinds of things that actually make digital lighting much less of a pain in the neck than real-world lighting, once you’ve got a handle on the tools.
[deleted and started a thread somewhere else with my questions]
I guess I was too quick. Well, whatever. The main point was whoever’s interested in digital lighting ought to read that book.
Also, by all means get the second edition, which I actually think is worth checking out even if you’ve already read the first edition, as there’s a lot of new material in it.
Ah, thank you, will definatly check this book out. Sorry about deleting the message, yes you were to fast
I will try playing with settings like no shadows, turning off specularity, etc. Thanks for the tips. I don’t know about it being less a pain in the neck, it will never beat pointing a spot at somebody’s face from a side and using a white surface to bounce it off to light soflty the other side of the face. Hehe
Floating point numbers for energy help when you are calculating the total light in a scene too. Generally, the sum of all the lights should equal 1.0. This way if you have two lights, you make them 0.5 each. Sometimes it’s appropriate to change this of course but it’s a rough guide to avoid over-saturating a scene.
Using quadratic fall-off is rarely useful because it cuts out the light far too quickly but linear fall-off seems to work ok. You should really only use zero fall-off for sunlight because if the light managed to travel 93 million miles then it’s hardly going to reduce intensity significantly over the few metres that people place sun lamps in their Blender scenes.
Of course, fall-off kind of makes using the energy values as a saturation guide a bit useless because you have to increase the light intensity by quite a lot.
This idea of just “simply” using real-world lamps is incredibly unrealistic. Go to your local lighting store and see just what they have available. You want one of each of those in Blender to keep everyone happy? And then there’s myriad light sources not available at the corner lighting store. There’s sunlight, moonlight, stage lights, traffic lights, street lights, firelight, candlelight, firefly light, torchlight, phosphorescent chemical light - in a variety of colours and amazing shapes and styles, starlight, TV light, lightning, gas light, limelight, LED and so on and so on and so on… If one person gets an incandescent lamp, another will want a fluorescent. Where does it end?
Of course, almost all of these can be readily approximated with what we already have in Blender - and with very little in-depth understanding of the physics of light.
Readily available digital lighting information as noted very recently…
Unless you are a very experienced set designer, I doubt you know off the top of your head how many lumens it takes to get a certain amount of light on an object 28.32 meters away. So even if Blender used some unit like lumens or watts or whatever, how would that help you? You would still have very little idea what number to use.
Almost everyone ends up rendering, adjusting the light, rendering again, etc. so it doesn’t really matter what units anything has, or whether they have units at all.
The only exception is when you consider distances, which actually matter in terms of shadows and physics simulations. For distances, I find it’s easiest to just consider 1 blender unit = 1 meter.
What the heck? Why does it matter that much how the light is measured? We’ve got energy units so that we can create lights easily and fairly accurately. As Andyd already said, you dont want to have to figure out how many watts(which is electricity, not actual light) it would take to light the sun. Also, a simple energy setting helps keep all types of lights easy to use. It would be stupid to have lighting measurments that are all different for each type of light.
Woa Andy and all. This hold on just faking it is just sick. a problem with having to rerender over and over is the start where incorrect lighting leads to re tooling.
I guess emit balls will do, but if they are to act as light they should go higher than 1.0
Very few people, if anyone, can know the ‘correct’ number to put in there no matter what units are used or how Blender does it. Re-rendering is part of creating a piece of artwork; you can only know the correct number once you see how the light interacts with the scene.
You also don’t need to re-render your entire scene; you can always use the box mode to create a quick preview of just a small section, taking only a few seconds to render.
Im saying that it would be a pain in the @$$ to try and figure out real liofe equivilants for CG. Where are their references for how strong the sun is in watts or wutever? Its not a hold on faking it. Its realizing what would be reasonable and simple to handle in CG.
but what really is a render preview? Their is no way you can get a real handlle on how the scene will look untill a full view is rendered. The 3d preview render window is nice but tiles are not fast.
like, hit shift-p in any 3d view. it renders the scene(in the 3d view) with no OSA, so its fast. I dont think it does shadows either, but its good for seeing how your lighting is working out. It also calculates AO, BTW. And since its siz eis customizable, you can just preview one part.
Thats what I was talking about.
It has no reaction to slider changes you have to get in the view and move things. Plus it cuts out if youre to close.
An IPR preview render would be better, tha is instant feedback
ture, but make good with what youve got.
And it actually can react o slider changes. Just hit f12 to render, then esc to stop the render. the preview will account for the changes. Its a little slower, but what are you gonna do?
