I am using Blinn's formula to do specular lighting with ARB_VP and ARB_FP.
For every vector(in ARB_VP):
1)I compute the light vector and normalize it.
2)I compute the view vector and normalize it.
3)I compute H=L+V,normalize H and store it in texcoord
For every fragment(in ARB_FP):
1)I get the interpolated texcoord,normalize it and store it in H.
2)I get the interpolated normal(N) from some other texcoord and proceed with the regular computations.
Now,for a reasonably large surface,the specular highlight is completely wrong.But,if i don't normalize the vectors in the vertex program and just keep the renormalization of H in the fragment program,the results look OK!
What do you think is happening?