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normalize joint weights #10539

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merged 3 commits into from
Jan 27, 2024
Merged

normalize joint weights #10539

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7a65ab4
normalize joint weights
robtfm Nov 13, 2023
3e87dff
Merge remote-tracking branch 'upstream/main' into normalize_mesh_weights
robtfm Nov 28, 2023
e5fa268
force negative weights to zero
robtfm Jan 27, 2024
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35 changes: 23 additions & 12 deletions crates/bevy_render/src/mesh/mesh/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -206,7 +206,7 @@ impl Mesh {
attribute: MeshVertexAttribute,
values: impl Into<VertexAttributeValues>,
) {
let mut values = values.into();
let values = values.into();
let values_format = VertexFormat::from(&values);
if values_format != attribute.format {
panic!(
Expand All @@ -215,17 +215,6 @@ impl Mesh {
);
}

// validate attributes
if attribute.id == Self::ATTRIBUTE_JOINT_WEIGHT.id {
let VertexAttributeValues::Float32x4(ref mut values) = values else {
unreachable!() // we confirmed the format above
};
for value in values.iter_mut().filter(|v| *v == &[0.0, 0.0, 0.0, 0.0]) {
// zero weights are invalid
value[0] = 1.0;
}
}

self.attributes
.insert(attribute.id, MeshAttributeData { attribute, values });
}
Expand Down Expand Up @@ -621,6 +610,28 @@ impl Mesh {
pub fn morph_target_names(&self) -> Option<&[String]> {
self.morph_target_names.as_deref()
}

/// Normalize joint weights so they sum to 1.
pub fn normalize_joint_weights(&mut self) {
if let Some(joints) = self.attribute_mut(Self::ATTRIBUTE_JOINT_WEIGHT) {
let VertexAttributeValues::Float32x4(ref mut joints) = joints else {
panic!("unexpected joint weight format");
};

for weights in joints.iter_mut() {
let sum: f32 = weights.iter().sum();
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Would it be worth verifying the weights are positive first? If someone accidentally uses with_inserted_attribute with a mixture of positive and negative floats, this will do weird things.

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negative weights are technically not allowed in the spec, whereas not summing to precisely 1 is allowed due to rounding issues.

but sure, no reason not to. i arbitrarily chose to clamp negatives to zero, i guess other treatments might be better (like if all are negative, maybe you should just flip the sign?) but since we're in invalid-data territory there's probably no perfect answer. if someone wants a different treatment they can always write their own normalize function.

if sum == 0.0 {
// zero weights are invalid
weights[0] = 1.0;
} else {
let recip = sum.recip();
for weight in weights.iter_mut() {
*weight *= recip;
}
}
}
}
}
}

#[derive(Debug, Clone)]
Expand Down