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Fix a typo at ȳ(547 nm) in CIE 1931 2° observer table

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The tabulated value was 0.9874812.
Per CIE 018:2019 Table 6 (DOI 10.25039/CIE.DS.xvudnb9b), the correct
value is 0.9874182.  Verification from CIE published data:

```
import urllib.request, csv, io

url = "https://files.cie.co.at/CIE_xyz_1931_2deg.csv"
data = urllib.request.urlopen(url).read().decode()

for row in csv.reader(io.StringIO(data)):
    if row and row[0].strip() == "547":
        print(f"y-bar at 547nm = {row[2]}")
        break
```

Signed-off-by: Jonathan Swartz <jonathan@jswartz.info>
This commit is contained in:
Jonathan Swartz 2026-04-23 11:19:11 +12:00
parent 8c19f30455
commit 247b2f38df
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src/pbrt/util/spectrum.cpp
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@ -403,7 +403,7 @@ const Float CIE_Y[nCIESamples] = {
0.8620000, 0.8738108, 0.8849624, 0.8954936, 0.9054432,
0.9148501, 0.9237348, 0.9320924, 0.9399226, 0.9472252,
0.9540000, 0.9602561, 0.9660074, 0.9712606, 0.9760225,
0.9803000, 0.9840924, 0.9874812, 0.9903128, 0.9928116,
0.9803000, 0.9840924, 0.9874182, 0.9903128, 0.9928116,
0.9949501, 0.9967108, 0.9980983, 0.9991120, 0.9997482,
1.0000000, 0.9998567, 0.9993046, 0.9983255, 0.9968987,
0.9950000, 0.9926005, 0.9897426, 0.9864444, 0.9827241,