{"record":{"id":"58eeedd031d146e6","repo":"FyroxEngine/Fyrox","slug":"vertex-size-cannot-be-larger-than-256-bytes","errorCode":null,"errorMessage":"Vertex size cannot be larger than 256 bytes!","messagePattern":"Vertex size cannot be larger than 256 bytes!","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"fyrox-impl/src/scene/mesh/buffer.rs","lineNumber":1256,"sourceCode":"}\n\n/// A trait for read-only vertex data accessor.\npub trait VertexReadTrait {\n    #[doc(hidden)]\n    fn data_layout_ref(&self) -> (&[u8], &[Option<VertexAttribute>]);\n\n    /// Clones the vertex and applies the given transformer closure to it and returns a stack-allocated\n    /// data buffer representing the transformed vertex.\n    #[inline(always)]\n    fn transform<F>(&self, func: &mut F) -> ArrayVec<u8, 256>\n    where\n        F: FnMut(VertexViewMut),\n    {\n        let (data, layout) = self.data_layout_ref();\n        let mut transformed = ArrayVec::new();\n        transformed\n            .try_extend_from_slice(data)\n            .expect(\"Vertex size cannot be larger than 256 bytes!\");\n        func(VertexViewMut {\n            vertex_data: &mut transformed,\n            sparse_layout: layout,\n        });\n        transformed\n    }\n\n    /// Tries to read an attribute with given usage as a pair of two f32.\n    #[inline(always)]\n    fn read_2_f32(&self, usage: VertexAttributeUsage) -> Result<Vector2<f32>, VertexFetchError> {\n        let (data, layout) = self.data_layout_ref();\n        if let Some(attribute) = layout.get(usage as usize).unwrap() {\n            let x = LittleEndian::read_f32(&data[(attribute.offset as usize)..]);\n            let y = LittleEndian::read_f32(&data[(attribute.offset as usize + 4)..]);\n            Ok(Vector2::new(x, y))\n        } else {\n            Err(VertexFetchError::NoSuchAttribute(usage))\n        }","sourceCodeStart":1238,"sourceCodeEnd":1274,"githubUrl":"https://github.com/FyroxEngine/Fyrox/blob/76c91aad8eca488ce527b1af707be8b3b24ad72d/fyrox-impl/src/scene/mesh/buffer.rs#L1238-L1274","documentation":"MeshBuffer::modify_vertices (and similar iterator helpers) copies the vertex data into a fixed-capacity ArrayVec of 256 bytes per vertex. Any vertex layout whose size exceeds 256 bytes cannot fit, so try_extend_from_slice fails and the code panics. This is a hard engine-side vertex size limit.","triggerScenarios":"Calling modify_vertices/modify on a vertex buffer whose VertexFormat layout totals more than 256 bytes per vertex (e.g. many custom attributes added via set_vertex_format).","commonSituations":"Custom shaders/materials with excessive per-vertex data (dozens of float4 attributes); procedurally generated buffers that pack large amounts of data per vertex instead of using textures or storage buffers.","solutions":["Reduce the vertex layout below 256 bytes: drop unused attributes or shrink formats (e.g. f32 -> u8 normalized)","Move bulk per-vertex data into textures or instanced attributes instead","Split the mesh into multiple buffers if the layout genuinely needs more data"],"exampleFix":"// before\nlayout.push(VertexAttribute::Float4x4 /* + many others, > 256 bytes */);\n\n// after\n// keep total layout under 256 bytes; move matrices to instance data\nlayout.push(VertexAttribute::Float3);","handlingStrategy":"validation","validationCode":"let size: usize = layout.iter().map(|a| a.size() as usize).sum();\nassert!(size <= 256, \"vertex layout too large: {} bytes\", size);","typeGuard":"fn vertex_size_ok(layout: &[VertexAttribute]) -> bool { layout.iter().map(|a| a.size() as usize).sum::<usize>() <= 256 }","tryCatchPattern":"// check layout size before modify_vertices; panics here are by-design limits\nif !vertex_size_ok(&layout) { /* reduce layout or split mesh */ }","preventionTips":["Keep per-vertex layouts small; prefer textures/instance data for bulk attributes","Compute layout byte size when defining custom formats","Never add attributes to a buffer without re-summing its size"],"tags":["panic","mesh","vertex-buffer","limit"],"backgroundTag":"value-out-of-range","analyzedSha":"76c91aad8eca488ce527b1af707be8b3b24ad72d","analyzedAt":"2026-09-10T16:04:01.633Z","contentChangedAt":"2026-09-10T16:04:01.633Z","schemaVersion":2},"datasetVersion":"2026-09-16T09:17:16.951Z"}