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Preserve MultiMaterial output in CSG mesh merges #299

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Merged
tracygardner merged 1 commit into from
Feb 15, 2026
Merged

Preserve MultiMaterial output in CSG mesh merges #299

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40 changes: 35 additions & 5 deletions api/csg.js
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Original file line number Diff line number Diff line change
Expand Up @@ -193,7 +193,7 @@ export const flockCSG = {
return null;
}

// Clone the first mesh's material for the merged result
// Keep a reference material only for fallback replacement.
const originalMaterial = referenceMesh.material;

// Try CSG2 first, fall back to simple merge if it fails
Expand Down Expand Up @@ -238,8 +238,8 @@ export const flockCSG = {
false,
true,
undefined,
false,
false
true,
true
);
}

Expand All @@ -254,8 +254,38 @@ export const flockCSG = {
mergedMesh.metadata.blockKey = blockId;
mergedMesh.metadata.sharedMaterial = false;

// Apply the original material
if (originalMaterial) {
// Preserve CSG/merge MultiMaterial output where possible.
// Only replace missing/default materials with a clone of the reference material.
const isDefaultMaterial = (material) => {
return (
material instanceof flock.BABYLON.StandardMaterial &&
material.name === "default material"
);
};

if (mergedMesh.material) {
if (mergedMesh.material instanceof flock.BABYLON.MultiMaterial) {
mergedMesh.material.subMaterials =
mergedMesh.material.subMaterials.map((subMaterial) => {
if (
subMaterial &&
isDefaultMaterial(subMaterial) &&
originalMaterial
) {
const replacement = originalMaterial.clone(
modelId + "_material",
);
replacement.backFaceCulling = false;
return replacement;
}
return subMaterial;
});
} else if (isDefaultMaterial(mergedMesh.material) && originalMaterial) {
const newMat = originalMaterial.clone(modelId + "_material");
newMat.backFaceCulling = false;
mergedMesh.material = newMat;
}
} else if (originalMaterial) {
const newMat = originalMaterial.clone(modelId + "_material");
newMat.backFaceCulling = false;
mergedMesh.material = newMat;
Expand Down