So, I'm following the Pixar tutorials on KhanAcademy, and thanks to that I'm now trying to make my own renderer. For this, I need to be able to determine whether a point I is inside, or outside a triangle in 3D space. I will be on the same plane as the triangle.
The way Pixar suggests using here, is weighted averages, which uses the formula: I = aA + bB + cC
With the three coordinates (Ix, Iy, Iz), it is possible to determine a, b and c, by solving the system of linear equations. When one or more of a, b, c is negative, I is outside of the triangle.
What I'm trying to do, is determining whether I is inside a triangle of which A, B and C have a Z-value of zero. Using the system of linear equations is not possible here.
How can I determine whether I is inside a triangle or not when all values of one axis are zero? I can just 'cut the axis off', but I was hoping there was a more easy way. I've taken a look at Check whether a point is within a 3D Triangle, but I didn't quite understand the answers given.
Thank you very much for trying to help me out! :)