In order to properly implement #29 and to match the raytraced output better, we want to integrate a strand thickness into the rasterized line output. Since there's no way to change the line thickness in the shader, we will either need to expand the line to a billboard, or simply just fade out the rasterized line at the tips to fake the strand becoming thinner. This last solution is of course limited, since the radius can't change throughout the hair geometry, but on the other hand, it is really simple. If we can get similar levels of performance using the billboard approach (I doubt it though), by expanding using the geometry shader, we can always use that.
In order to properly implement #29 and to match the raytraced output better, we want to integrate a strand thickness into the rasterized line output. Since there's no way to change the line thickness in the shader, we will either need to expand the line to a billboard, or simply just fade out the rasterized line at the tips to fake the strand becoming thinner. This last solution is of course limited, since the radius can't change throughout the hair geometry, but on the other hand, it is really simple. If we can get similar levels of performance using the billboard approach (I doubt it though), by expanding using the geometry shader, we can always use that.