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Refraction

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This is a paragraph from a tutorial i've read Next, we calculate the refraction. If you remember your highschool physics, you know that: refraction index = sin( angle of incoming light ) / sin( angle of refracted light ) so that the angle of the refracted beam can be calculated like this: angle of refracted light = arcsin( sin( angle of incoming light ) / refraction index ) where the refraction index is that of water: 1.33. Third, we need to calculate where the refracted beam hits the image, or its relative position to the place where the incoming light beam originally entered: displacement = tan( angle of refracted beam ) * height difference Could you tell me how is the displacement computed,i can't understand it.[looksaround] Thanks!

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No refractive difference.

\ /
\ /
\ /
----------------
\ /
\/
----------------


Some refractive difference.


\ /
\ /
\ /
----------------
`. .`
`.`
----------------


Notice the path of the light once it exits the substrate, compared to the original it has displaced to the right. If you do the trig to find the difference then its the above equation.

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Well i'm intereasted in both :how it would look and how to implement it into code.
Let's say i have a newspaper under the water and a source of light:

L
\a
\ | n - ----------------------------
\| - /---- /----------------------water
| -------- /--------------water
|. -/----------------------------
| ./ /
b _ _ _

"a" is the angle between the light source and the surface normal
"b" is the angle of refraction(that thing under the water is the newspaper)
L n(normal)
\a|
\D
--------------- |A
|.\ |
|b'\ |height
|--'\*---------- |B
C N M

-lets say bis greater than air 1.003 so the light does not hit*M but N
so does this means that tan(b)=(CM-displacement)/height;so
displacement=........How do i light the underneath surface..(texture)
Do i have to bring the refracted ray into the texture space?
How do i do that ??[looksaround] or if you have a better idea please let me know .

Thanks a lot!
>

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