From 24128078c5ab11851d4529327c2c03820e9c26d0 Mon Sep 17 00:00:00 2001 From: Tyler Perkins Date: Thu, 10 Nov 2022 20:30:01 -0500 Subject: [PATCH] Update for 10-11-22 20:30 --- tech/light_transport.wiki | 52 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/tech/light_transport.wiki b/tech/light_transport.wiki index 8c16ce8..1451999 100644 --- a/tech/light_transport.wiki +++ b/tech/light_transport.wiki @@ -32,3 +32,55 @@ How do we calculate how much light exits a surface point in a given direction [[maxwell_equations|Maxwell equations]]! +In practive, we dont do that. We try to think of light as a ray unless we have +to + +Instead we use the rendering equation! + +Terms used in diagrams + +* V - direction towards the viewer +* N - surface normal +* L - vector pointing towards the light source +* R - reflected ray direction +* Theta,,i,, and Theta,,r,, - incident and reflected angles + +To calcuate R `R = L - 2N(L * N)` + +== Light attentuation == + +* The amount of intensity light looses as it travels farther away. Light looses + energy as well as it reflects off of surfaces +* How can we calculate attentuation? + +`L * N` + +Assuming that L and N are normalized, the attentuation will be equal to +`cos(theta)` where theta is the angle between L and N. This is true because of +the dot product. + +== Materials == + +How can we simluate the look of different materials? + +Based on how they relfect light. + +* Specular surface reflects exactly one ray + * One incoming direction + * One outgoing direction +* Diffuse spreads ray into smaller rays in all directions + * On incoming direction + * many outgoing direction + * many outgoing intesntiy +* Spread breaks out the ray into a few smaller rays in a single direction + +To simulate a surface, we can use a probability density function that takes + +* incoming light direction +* point on surface + +This method will output the _probability of a given outward direction_ + +Something like `probability of happening = f(incoming direction, point, outgoing direction)`. + +This is known as the _Bidirectional reflectance distribution function (BRDF)_.