BabylonJS/Babylon.js · error · Error

Draco: Cannot decode invalid geometry type ${type}

Error message

Draco: Cannot decode invalid geometry type ${type}

What it means

DecodeMesh switches on decoder.GetEncodedGeometryType(buffer) and only handles TRIANGULAR_MESH and POINT_CLOUD. Any other (or unknown) geometry type falls into the default branch and throws this Error, because Babylon has no decoding path for it.

Source

Thrown at packages/dev/core/src/Meshes/Compression/dracoCompressionWorker.ts:236

                } finally {
                    decoderModule._free(ptr);
                }

                geometry = mesh;
                break;
            }
            case decoderModule.POINT_CLOUD: {
                const pointCloud = new decoderModule.PointCloud();
                status = decoder.DecodeBufferToPointCloud(buffer, pointCloud);
                if (!status.ok() || !pointCloud.ptr) {
                    throw new Error(status.error_msg());
                }

                geometry = pointCloud;
                break;
            }
            default: {
                throw new Error(`Draco: Cannot decode invalid geometry type ${type}`);
            }
        }

        const numPoints = geometry.num_points();

        const processAttribute = (decoder: Decoder, geometry: Mesh | PointCloud, kind: string, attribute: any /** Attribute */) => {
            const dataType = attribute.data_type();
            const numComponents = attribute.num_components();
            const normalized = attribute.normalized();
            const byteStride = attribute.byte_stride();
            const byteOffset = attribute.byte_offset();

            const dataTypeInfo: Record<number, { typedArrayConstructor: TypedArrayConstructor; heap: TypedArray }> = {
                [decoderModule.DT_FLOAT32]: { typedArrayConstructor: Float32Array, heap: decoderModule.HEAPF32 },
                [decoderModule.DT_INT8]: { typedArrayConstructor: Int8Array, heap: decoderModule.HEAP8 },
                [decoderModule.DT_INT16]: { typedArrayConstructor: Int16Array, heap: decoderModule.HEAP16 },
                [decoderModule.DT_INT32]: { typedArrayConstructor: Int32Array, heap: decoderModule.HEAP32 },
                [decoderModule.DT_UINT8]: { typedArrayConstructor: Uint8Array, heap: decoderModule.HEAPU8 },

View on GitHub (pinned to 0592b347b8)

Solutions

1. Validate the input is genuine Draco data before decoding (magic bytes / known source).
2. Re-export the asset ensuring it is encoded as a mesh or point cloud.
3. Check for buffer truncation that corrupts the geometry type field.
4. If the type is valid but unsupported by Babylon, decode it with the raw Draco module directly instead.

Example fix

// before
const geo = await DecodeMesh(buffer); // buffer is not Draco -> type = -1

// after
function isLikelyDraco(buf: ArrayBuffer) { return buf.byteLength > 5; } // plus real validation
if (isLikelyDraco(buffer)) {
  const geo = await DecodeMesh(buffer);
}

// decode and inspect geometry type before relying on Babylon's worker
type === decoderModule.TRIANGULAR_MESH || type === decoderModule.POINT_CLOUD
  ? proceed : reject('unsupported Draco geometry type: ' + type);

const isSupportedGeometryType = (type: number): type is 0 | 1 =>
  type === 0 /* TRIANGULAR_MESH */ || type === 1 /* POINT_CLOUD */;

try {
  geometry = await DecodeMesh(buffer);
} catch (e) {
  if (String(e?.message).includes('invalid geometry type')) {
    throw new Error('Asset is not a decodable Draco mesh/point cloud; check source data');
  }
  throw e;
}

When it happens

Trigger: Decoding a Draco buffer whose encoded geometry type is neither TRIANGULAR_MESH nor POINT_CLOUD (e.g. invalid/corrupted data causing GetEncodedGeometryType to return an unexpected value, or a future/unknown Draco geometry type).

Common situations: Corrupted headers making the type byte garbage; decoding arbitrary binary data that merely resembles Draco; using a decoder that returns -1/INVALID for failed type detection.

Related errors

• The provided data is not a valid KTX2 file.
• Failed to decode the KTX2 file: expected ${layerCount} layer
• Draco: Missing position attribute for encoding.
• status.error_msg()
• Draco: Cannot decode invalid data type ${dataType}

AI-assisted analysis of BabylonJS/Babylon.js@0592b347b8 (2026-08-30). Data as JSON: /api/errors/5ed7aa5e0993687f. Report an issue: GitHub.