I am tring to use half vector to calculate highlight, but it's wrong result, I can't find what's wro

Unity Engine
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1

This is right way, it produce right result
7080700--842503--upload_2021-4-27_10-20-24.png

7080700--842506--upload_2021-4-27_10-21-7.png
7080700--842506--upload_2021-4-27_10-21-7.png831×382 5.81 KB

Now, I want to use half vector to do same thing, It produce a pure black result
7080700--842509--upload_2021-4-27_10-21-52.png

7080700--842512--upload_2021-4-27_10-22-24.png
7080700--842512--upload_2021-4-27_10-22-24.png826×383 2.18 KB

2

I found the problem, halfDir was a float value, it should be float3. omg