Override3D

Override3D takes a required SceneInput carrying classic Fusion scene3d and returns Output of the same type. It is neither a geometry generator nor Renderer3D: it changes object properties inside the scene without creating RGBA pixels.

Blackmagic describes the Controls tab around a literal Do [Option] + [Option] pattern. First the Do checkbox enables an override, then the corresponding property value becomes active. While Do is off, the upstream object's value should pass through unchanged.

That distinction matters. In Override3D the Do flag is not the final property state; it grants the node permission to replace that state. Do Visible = Off therefore means 'do not override Visible,' not 'make the object invisible.'

Override3D acts across the objects contained in its incoming scene. This makes it powerful after Merge3D when one downstream switch should affect a group, while a branch-specific override is often clearer before the final Merge3D.

Blackmagic specifically calls out Override3D as the way to set wireframe, visibility, lighting, matte and ID options on 3D particle systems and Text3D. Those generators do not expose every common object property directly in their own Inspectors.

Wireframe override changes how geometry is displayed/rendered as a mesh outline. It is a diagnostic object/render property rather than Weld/Triangulate topology work and it does not convert a mesh into Ribbon3D-style line geometry.

Visible is the strongest object-visibility flag. The common 3D controls state that disabling Visible removes the object from viewers and Renderer3D output and also prevents it from casting shadows. Visible Off is therefore not a shadow-only setup.

Unseen by Cameras is separate. The object remains present in the 3D Viewer but is omitted from camera/final rendering. Its shadow semantics are renderer-specific: the documented Software Renderer can keep shadows from an unseen object, while the OpenGL renderer does not.

Cull Front Face and Cull Back Face control polygon culling by orientation. Blackmagic notes that culled faces do not render or cast shadows; enabling both front and back culling has the same visible effect as disabling Visible.

Suppress Aux Channels for Transparent Pixels controls whether fully transparent pixels contribute auxiliary data such as Z, normals and UVs. If a downstream depth, texture-replacement or pass workflow needs auxiliary information under transparent RGBA, changing this flag can remove required data.

Affected by Lights is object-level lighting participation. The documented common behavior when it is disabled is broader than simply 'no diffuse light': scene lights stop affecting the object, it neither receives nor casts shadows, and it is displayed at the full brightness of its color, texture or material.

Shadow Caster and Shadow Receiver separately override shadow participation when the rest of the lighting setup permits it. Neither checkbox creates a shadow map by itself; a compatible light, receiver/caster and Renderer3D shadow configuration are still required.

Matte override applies Fusion's 3D matte/holdout behavior. The common Is Matte semantics make the object itself camera-invisible and also remove geometry that lies behind it in Z. That is fundamentally different from setting a material Opacity to zero. Conditional matte child controls such as Opaque Alpha and Infinite Z depend on the expanded state and remain target-build UI checks.

The Normals/Tangents section is diagnostic display only: Scale changes guide length while Show Normals and Show Tangents toggle surface-vector visualization. It does not recompute vector data; ReplaceNormals3D is the tool for recalculation.

Do Object ID and Do MaterialID override numeric auxiliary IDs on affected geometry/material state. Those IDs become useful in Renderer3D auxiliary-channel or downstream selection workflows, but assigning an ID does not automatically produce an RGBA matte.

Do Blend Mode overrides object blend behavior. Fusion's common 3D controls distinguish OpenGL/Hardware and Software blend paths, so a named mode should not be assumed to have identical availability or behavior across renderer types without a controlled test.

Exclusions / Limit by Object ID and Limit by Material ID narrow the Override3D scope. The captured current Inspector confirms both checkboxes. Their target ID fields appear conditionally; exact labels/defaults and combined-limit behavior remain live target-build verification rather than invented values.

Override3D does not change vertex positions, face topology, UV coordinates, normal/tangent data, material shader graphs or camera transforms. Use Weld3D/Triangulate3D for topology, UVMap3D for texture coordinates, ReplaceNormals3D for surface vectors and ReplaceMaterial3D for surface shading.

Blackmagic's documented example pairs Override3D with ReplaceMaterial3D for isolated technical passes: Override changes object-level flags such as Affected by Lights while ReplaceMaterial3D supplies a replacement surface. The two tools operate on different layers of the same scene.

Override3D.Output remains scene3d. It can feed Merge3D, ReplaceMaterial3D, Transform3D, Renderer3D or another compatible 3D processor. Direct Output → MediaOut or a normal 2D Merge is a type mismatch; Renderer3D is the scene-to-image boundary.