Clarification on Light implementation

dilevin / computer-graphics-ray-tracing

Computer Graphics Assignment about Ray Tracing

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Clarification on Light implementation #19

Open ginkxo opened 4 years ago

ginkxo commented 4 years ago

Regarding directional light vs. point light:

We have to calculate vector direction "d" pointing to the direction of the light source just from the information in the query "q"?
does "q" as a query point refer to the actual position of an object being hit by a ray in 3d space, or something else?
how exactly do we interpret max_t here? if max_t is infinite, then it means the light source is extremely far away, but if it is a value say < 1.0 the light source position d is very close? and max_t is something that needs to be calculated based off of just object position as well?

thanks!

rarora7777 commented 4 years ago

I'd give a hint here since some of you may be new to C++ or Object-Oriented Programming:

The function PointLight::direction (or DirectionalLight::direction) is a member function of the PointLight (or DirectionalLight) class. So, you also have access to the member variables (also known as fields) of the object for which the function is called. This means that you also have access to properties of that light, and not just the parameter (q) explicitly passed to the function.

Look at PointLight.h (or DirectionalLight.h) to see what properties are available to you.

rarora7777 commented 4 years ago

max_t is the parametric distance of the query point q from the light source. For a point light, this will be the value of the parameter t along the light ray. For a directional light, the README tells you precisely what value you need to set here. 😉

ginkxo commented 4 years ago

right, I was getting confused over how the d field in specifically DirectionalLight was both being used as a "direction from the light towards the scene" but we also return d as a "direction towards the light" in our .direction implementations. I'm assuming now that since PointLight has its member variable called p that this was just a case of variable naming I accidentally overlooked. thanks for the help!