handle non-invertible matrix (may be caused by zero scale for instance)

Author: Wumpf

crates/viewer/re_renderer/src/renderer/mesh_renderer.rs

@@ -220,8 +220,15 @@ impl MeshDrawData {
                     count_with_outlines += instance.outline_mask_ids.is_some() as u32;
 
                     let world_from_mesh_mat3 = instance.world_from_mesh.matrix3;
+                    // If the matrix is not invertible the draw result is likely invalid as well.
+                    // However, at this point it's really hard to bail out!
+                    // Also, by skipping drawing here, we'd make the result worse as there would be no mesh draw calls that could be debugged.
                     let world_from_mesh_normal =
-                        instance.world_from_mesh.matrix3.inverse().transpose();
+                        if instance.world_from_mesh.matrix3.determinant() != 0.0 {
+                            instance.world_from_mesh.matrix3.inverse().transpose()
+                        } else {
+                            glam::Mat3A::ZERO
+                        };
                     instance_buffer_staging.push(gpu_data::InstanceData {
                         world_from_mesh_row_0: world_from_mesh_mat3
                             .row(0)

crates/viewer/re_space_view_spatial/src/contexts/transform_context.rs

@@ -555,8 +555,14 @@ fn query_and_resolve_tree_transform_at_entity(
     if let Some(mat3x3) = result.component_instance::<TransformMat3x3>(0) {
         transform *= glam::Affine3A::from(mat3x3);
     }
+
     if result.component_instance::<TransformRelation>(0) == Some(TransformRelation::ChildFromParent)
     {
+        if transform.matrix3.determinant() != 0.0 {
+            // TODO(andreas): Should we warn? This might be intentionally caused by zero scale.
+            transform = transform.inverse();
+        }
+
         transform = transform.inverse();
     }