When trying to find the intersection of a ray and a parallelogram, in Derek Elkins left SE answer he states you can simply do 2 ray triangle intersections
Where he is explaining how to do a ray parallelogram intersection he specifies if,
- $t>0$
- $0\leq\alpha\leq1$
- $0\leq\beta\leq1$
If $\alpha$ and $\beta$ are in that range aren't you already solving for the parallelogram intersection so the statement about doing "2 ray - triangle intersections" is irrelevant as his method already applies to a parallelogram?
This now begs the question what would the range of $\alpha$ and $\beta$ be if you are trying to find a ray - triangle intersection? My intuition tells me the range would be $$0\leq\alpha+\beta\leq1,\alpha\geq0,\beta\geq0$$
