How do you determine angle of incidence?
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When you are determining what angle a photon reflects off of a surface in TPT, how do you do that? What algorithm? I mean you are dealing with individual pixels (raster graphics) and not vector graphics, so you don't have any actual measurement of the angle of any line, because there really are no lines in this, just an arrangement of pixels that may constitute a line. To measure an angle you need the surface to have an actual line (represent the line by a line equation). So how does TPT convert from raster-graphics to vector-graphics on the fly, in order to calculate the angles of incidence and reflection with photons?
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@Videogamer555 (View Post) The velocity is a vector, so you can use that.
The exact code is https://github.com/simtr/The-Powder-Toy/blob/master/src/simulation/Simulation.cpp at line 4199 ish.
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@Emperor_Bowserinator (View Post)
Yes, but the object that the photon may strike is not a vector. It's not a line as described by a line equation. It is a set of pixels. How does the angle of the surface of the object get determined, so as to be able to calculate the new velocity vector of the photon after the collision between the photon and the object? -
@Videogamer555 (View Post)
I'm not entirely sure if this is what you are looking for, but here is my method:
Using the two numbers I got,
90.391° is pretty close to 90°Edited 4 times by Mrprocom. Last: 4th Feb 2016 -
By a quick glance, I'd say Simulation::get_normal_interp has something to do with it. Haven't mustered the strength yet to make sense of the uncommented code.
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@Videogamer555 (View Post) My guess is you can estimate that by taking the surrounding few pixels, get the height and width difference and estimate an average angle.
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The idea is to approximate the boundary based on the particles, and find the line normal in the reflection point based on that. Takes
I think these two functions might be of interest:
https://github.com/simtr/The-Powder-Toy/blob/master/src/simulation/Simulation.cpp#L2564
https://github.com/simtr/The-Powder-Toy/blob/master/src/simulation/Simulation.cpp#L2535
However, this is probably written by Skylark who idles around IRC all the time, so you can ask for more there if you're really interested. Also check out this on finding normals to lines in 2D space:
http://stackoverflow.com/a/16417931/2278637
