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Full Version: WIP Lighting theory tutorial.
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I've started putting this together in my free time.

Give it a look and pick it to pieces, if anything doesn't make sense point it out, or if my information is wrong, point it out.

I'm partially putting this together as a test of my knowledge on the subject as well as a teaching mechanism.
We've already found some things wrong with my terminology, which I've fixed.

Light intensity falls off at a geometrical rate, not an exponential.

Though light hitting a plane is exponential in intensity based on angle.
Okay, when I read "you know already how to mentally construct how light hits an object" I thought "Oh no," cause that's what I'm trying to learn!

I like how you started with a simple case and started working up, and how you defined all your terms and assumptions up front. Like a science paper.

And I loved the "Colour: the correct way to spell “color.”"

I've never heard of the geometrical falloff, but it is starting to make sense.

It might help if you label your pictures under the "The beam is lighting a flat surface" with degrees, starting at 0 degrees. It actually took me a while to figure out that the 0 to 90 degrees in your 3D light source example meant 0 degrees faces light directly, 90 degrees is when the strip is parallel to light rays.

To try it in the real world, I got a little cardboard box, held it up to a light (0 degrees) and rotated it at a fairly constant angular speed to 90 degrees. Sure enough, you can see it gradually, gradually darken a bit, then all of a sudden go dark! Even though you don't speed the rotation, the darkening happens fast at the end. Learn a new thing every day!

So thank you for posting! I'd love to see the final version!

p.s. I assume you'll label the figures eventually, so they're easier to reference.
Thanks for the feedback! This is exactly the sort of thing i want to hear.

Working out what is intuitive and what needs specific labeling can be somewhat difficult. So I'll fix that up tonight. And i also want to supplement the 3d examples with real world examples as well.

3d is a great way to remove variables from the equation to help explain things easier, but it still has some caveats that aren't perfect analogues in the real world.

Tonight i want to write the next section on exposure and gamma, which will be pretty difficult to write, as it changes how harsh the terminator line is. It's probably going to force me to also have to do some math to make sure everything i am saying is spot on.
I was ready James Gurneys book on lighting.

It kind of makes me feel justified in making this as i actually feel like it justifies my thoughts that a no nonsense light and colour tutorial needs to exist.

Even though the book is lovely and is covered in insights and is for the most part scientifically accurate, i don't understand why first principles are presented as different areas. For example why is light filtering a different subject than atmospheric perspective? They are exactly the same thing, just different examples of it in the real world.

I think this is a big project to take on, and to make it as good as i want it to be it's going to need a lot of revision as well as i need to step up my game on the art side of things to prove i know what i am talking about.
Wow, I looking at all the sections you'll be putting in there--really thorough!

So...I really know nothing about lighting, but had a question on the specular. I think I misunderstood how it's written. I'm not sure the "picture a mirror dead center on the light source, there's the specular" works, because incident angle = reflected angle.

For example, say you have a small light, pointed straight down at the ground. You are looking straight ahead. If you hold a mirror in the beam facing up to the light, you'd have to rotate it 45 degrees toward you to see the light.
Yeah, you are correct, i may have just worded it badly!

A good exercise is to pull up a photo and find all the specular highlights, then work out what angle the planes they are illuminating is on. You will notice that the planes are all at very similar angles.
Btw i'm still working on this.

I've got a list of all the example images i need to make. I think they are going to tax me harder than any artistic challenge I've ever set myself.
Need to prove that this info is all correct :P.
Oh good, I'd really like to see how it turns out!