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Fix float imprecision on blend weights

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This commit is contained in:
ackwell 2024-05-04 04:01:28 +10:00
parent 46a111d152
commit 7553b5da8a
1 changed files with 21 additions and 1 deletions
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22
Penumbra/Import/Models/Import/VertexAttribute.cs
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@ -138,7 +138,27 @@ public class VertexAttribute
return new VertexAttribute(
element,
index => BuildNByte4(values[index])
index => {
// Blend weights are _very_ sensitive to float imprecision - a vertex sum being off
// by one, such as 256, is enough to cause a visible defect. To avoid this, we tweak
// the converted values to have the expected sum, preferencing values with minimal differences.
var originalValues = values[index];
var byteValues = BuildNByte4(originalValues);
var adjustment = 255 - byteValues.Select(value => (int)value).Sum();
while (adjustment != 0)
{
var convertedValues = byteValues.Select(value => value * (1f / 255f)).ToArray();
var closestIndex = Enumerable.Range(0, 4)
.Select(index => (index, delta: Math.Abs(originalValues[index] - convertedValues[index])))
.MinBy(x => x.delta)
.index;
byteValues[closestIndex] = (byte)(byteValues[closestIndex] + Math.CopySign(1, adjustment));
adjustment = 255 - byteValues.Select(value => (int)value).Sum();
}
return byteValues;
}
);
}