[Artifex]

There's a lot of great advice and analysis in that thread along with Fred's initial post. I think it'd help a lot of people to read it if they haven't seen it already. I could start a new thread, if everyone would prefer that.

Can I get some admin input on this?
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Artifex

[Lev_0]

Hey, why not start a new thread and just link to whatever other threads you think would be important. All of my images in this thread are going down this month since I'm taking down the site where the images are hosted. They should be back up soon after I find somewhere else to put them.

[flying_v]

A bit late but just wanted to point out that in the above image, A is indeed the one and only reflection and B is simple illumination; meaning the light is illuminating the left surface directly and that's why it's light.

Reflections always go straight to your eye on the surface they form. Imagine a full moon over a lake, the reflection will go straight at you no matter where you move. The reason is that the light is bouncing directly to your eye at that place (that's why it follows you, and that's why it's so bright), everywhere else it's bouncing and getting lost into the atmosphere.

[nuclearbum]

sorry if this is really late, but i think it's interesting info that may help in understanding how light interacts with our world (or how our world likes to interact with light )

the illumnation from b is based on the intensity of light (specular highlight). basically what you see there is what is happening to the whole wall for use to see it. the brightness is due to the distance from the light source, not the angle that the light hits it (reflections depend on that).

why so bright and then a quick falloff? basically less photons (a particle of light) are hitting each point on the wall as the distance from the source increases. this type of relationship is given a name, called the inverse square relationship. for you math nerds, you can model this with I=P/R�, where "I" is the intensity (power/area) of light "R" centimeters (distance) away from a light souce of "P" watts (power). (side note: that equation assumes a spherical source where light is evenly distributed. if the power is not constant, you'll have to come up with a power function that describes the power output over the surface. if the source is a different shape than a sphere, you'll have to find a function relating power to the change in distance a small distance (dR) and then intergrate over the min distance to the max distance.) that equation also models intensity of sound (volume) over distance too

so basically what the "relfection" of B is telling us is how many photons are hitting the wall at that point from the light source. and we can see them based on previous explanation of light scattering.

the reflection A is an anisotropic reflection. what that means is that the surface is scratched or really bumpy (think seeing a stretched reflection of the moon on the ocean). this is a little harder to explain, but think of it as if there are a bunch of mirrors linedbute at an angle like this /////. each mirror reflects about the same thing, and what we see is a little bit of overlap with the reflection. thus creating the effect of a stretched reflection, which can be confused with a specular highlight.
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