Improve Vector Depth Test Sampling. For inside Corners

[kevancress]

I could probably use some of the techniques from here: https://github.com/ssloy/tinyrenderer/wiki/Lesson-1:-Bresenham%E2%80%99s-Line-Drawing-Algorithm

and here: https://github.com/ssloy/tinyrenderer/wiki/Lesson-2:-Triangle-rasterization-and-back-face-culling

to improve my vector depth sampling. Getting the pixel with the least error distance to the vector, line and sampling it, rather than aggregating samples from all adjacent pixels should be more accurate and faster.

[kevancress]

Started in 3b78e21