Why does a plane, that's facing 0,0,0, with origin, 0,0,-10, have a negative z in its normal?

[alurpal]

Shouldn't its normal be 0,0,1?

In your example scene, the back wall has a normal of 0,0,-1

Backstory: I'm using your code and implementing triangles using https://www.scratchapixel.com/lessons/3d-basic-rendering/ray-tracing-rendering-a-triangle/ray-triangle-intersection-geometric-solution as reference. I got it to work and then realized my normals were going opposite than I thought (mind boggling). Anyway, I was under the impression that the normal was the direction an object's plane was facing.

[SebastianFelgueras]

It is the same, since the plane is orthogonal to the normal vector, the only relevant thing is the direction of the normal, not if it's pointing forward or backwards