half vector in pixel shading

[jorge1774]

Hi all!

Can someone explain why linear interpolation of half angle vector produces worst results than interpolating POINT TO EYE vector, then calculating half angle vector by pixel?

I still can't imaging why is that...

See you.

[ehart]

The half-angle vector varies non-linearly. It is the normalized sum of two normalized vectors. If you work aout the math of the lerp of the half angles versus the half angle of the lerped vectors, you will see that they simply aren't equivalent.

-Evan

[jorge1774]

Hi and thanks for your answer.

I was thinking in that, and I took my old algebra books to find something similar.

See you.