Clamp scalar range in docs for surface sampling

[MatthewFlamm]

closes #134

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (9fa26a5) 99.13% compared to head (75f24cf) 99.13%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #135 +/- ## ======================================= Coverage 99.13% 99.13% ======================================= Files 5 5 Lines 345 345 ======================================= Hits 342 342 Misses 3 3 ```

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