bevyengine/bevy · error · MeshAttributeCompressionError

Vertex attribute {attr:?} must have format {expected:?} befo

Error message

Vertex attribute {attr:?} must have format {expected:?} before compressing/quantizing

What it means

MeshAttributeCompressionError::UnsupportedAttributeForCompression is thrown when an attribute's current VertexFormat is not one the compression/quantization path can accept as input. The library expects a specific source format (the expected field) before it can compress the attribute's data.

Source

Thrown at crates/bevy_mesh/src/mesh.rs:3181

                        return None;
                    };
                    Some((id, data))
                })
                .collect()),
            indices: serialized_mesh.indices.into(),
            ..Mesh::new(serialized_mesh.primitive_topology, RenderAssetUsages::default())
        }
    }
}

/// Error that can occur when compressing/quantizing mesh vertex attributes.
#[derive(Error, Debug, Clone)]
pub enum MeshAttributeCompressionError {
    #[error("Vertex attribute {0:?} doesn't exist")]
    MissingAttribute(MeshVertexAttributeId),
    #[error("Vertex attribute {0:?} must not be empty")]
    EmptyAttribute(MeshVertexAttribute),
    #[error(
        "Vertex attribute {attr:?} must have format {expected:?} before compressing/quantizing"
    )]
    UnsupportedAttributeForCompression {
        attr: MeshVertexAttribute,
        expected: VertexFormat,
    },
    #[error("Vertex attribute {attr:?} must have format `Float32`, `Float32x2` or `Float32x4` before quantizing")]
    UnsupportedAttributeForQuantizing { attr: MeshVertexAttribute },
}

/// Error that can occur when calling [`Mesh::merge_duplicate_vertices`]
#[derive(Error, Debug, Clone)]
pub enum MeshMergeDuplicateVerticesError {
    #[error("Index attribute already set.")]
    IndicesAlreadySet,
    #[error("Mesh access error: {0}")]
    MeshAccessError(#[from] MeshAccessError),
}

View on GitHub (pinned to 8d743eb7dc)

Solutions

1. Read the expected VertexFormat from the error and convert the attribute to that format (e.g. via Mesh::transform_attribute_data / reinterpret helpers) before compressing
2. Only compress uncompressed source formats (typically Float32 variants); skip attributes already in a compressed format
3. Audit your pipeline for double-compression and guard with a format check before calling compress
4. Ensure the attribute was inserted with the correct VertexFormat when building the mesh

Example fix

// before
mesh.compress_attribute(Mesh::ATTRIBUTE_POSITION.id);
// after
if mesh.attribute(Mesh::ATTRIBUTE_POSITION.id).map(|a| a.format()) == Some(VertexFormat::Float32x3) {
    mesh.compress_attribute(Mesh::ATTRIBUTE_POSITION.id);
}

fn format_is(mesh: &Mesh, id: MeshVertexAttributeId, expected: VertexFormat) -> bool {
    mesh.attribute(id).map(|a| a.format()) == Some(expected)
}

match result {
    Err(MeshAttributeCompressionError::UnsupportedAttributeForCompression { attr, expected }) => {
        warn!("reformat {:?} to {:?} before compressing", attr, expected);
    }
    _ => {}
}

When it happens

Trigger: Calling Mesh::compress_attribute (or quantize) on an attribute whose VertexFormat differs from the expected format returned in the error — e.g. the attribute was already compressed, inserted with a non-float format, or its format was changed earlier.

Common situations: Running compression twice on the same mesh; authoring meshes with normalized/integer formats (Unorm8, Snorm16, etc.) and then attempting compression; converting an asset pipeline that changes formats upstream.

Related errors

• Color compression flag must be `COMPRESS_COLOR_FLOAT16` or `
• Source mesh position data is not Float32x3
• Attribute "{0}" has unexpected format {1:?}
• Failed to insert attribute. Invalid attribute format for {}.
• Mismatched vertex attribute values

AI-assisted analysis of bevyengine/bevy@8d743eb7dc (2026-09-13). Data as JSON: /api/errors/b8acf394c74f81d1. Report an issue: GitHub.