ReplaceMaterial3D

ReplaceMaterial3D has a required SceneInput and returns scene3d through Output. It is a material processor inside the 3D pipeline; there is no RGBA image output until Renderer3D.

Blackmagic describes the tool as replacing materials on geometry in the input scene while lights and cameras pass through unaffected. That makes it valid after a single Text3D/Shape3D branch or after Merge3D when the replacement should be filtered inside an assembled scene.

MaterialInput is a separate polymorphic input. It accepts either a 2D image or a 3D material, and those two cases have different Inspector semantics rather than being one generic 'material picture' path.

When a normal 2D image is connected to MaterialInput, Blackmagic uses it as the diffuse texture map for ReplaceMaterial3D's built-in Basic Material. The remaining built-in surface response—specular, transmittance, lighting response and MaterialID—still belongs to that material workflow.

When a real 3D material such as Phong.Material is connected, the built-in Basic Material is disabled and the Material tab becomes an external-material indication. The connected shader is therefore not merely an extra texture layer on top of a simultaneously active built-in Diffuse/Specular material.

With MaterialInput empty, ReplaceMaterial3D can use its built-in material directly. This is useful for a quick diffuse/specular/opacity override without creating a separate material node.

Replace Mode controls Red, Green, Blue and Alpha independently. Each channel offers Keep, Replace, Blend and Multiply. Keep preserves the original-material channel, Replace uses the replacement-material channel, Blend mixes them, and Multiply multiplies them.

Per-channel Replace Mode is not the object/material-selection mechanism. First the tool decides which geometry is in scope; then each channel mode decides how the original and replacement materials are combined on that selected geometry.

Limit by Object ID filters the replacement using the Object ID already carried by incoming geometry. When enabled, a target Object ID is selected. This is a selection filter, not a control for assigning a new Object ID.

Limit by Material ID similarly filters by the source Material ID assigned to incoming surfaces. It is especially useful on imported FBX/Alembic assets or geometry that contains several material assignments.

When both Object ID and Material ID limits are enabled, the reference states that both conditions must be satisfied. Treat the scope as an AND-like selection rather than two independent replacement passes.

Do not confuse Controls / Material ID limit with Material tab / MaterialID. The former selects which existing material is eligible for replacement; the latter assigns an ID to the replacement material itself for downstream MaterialID render passes.

Controls / Enable turns on the material-replacement effect. Blackmagic explicitly distinguishes this checkbox from the general red tool switch in the Inspector header: the red switch disables the tool as a whole, while Enable belongs to the effect portion of ReplaceMaterial3D.

Diffuse Color is the base diffuse response of the built-in Basic Material. With a 2D MaterialInput image, that image becomes the diffuse texture map, so the texture and built-in diffuse controls belong to one material workflow rather than two separate composites.

Diffuse Alpha and Opacity contribute to built-in-material transparency, but the final result also depends on Alpha Mode. With Alpha Mode set to Keep, changing replacement alpha does not mean the original alpha channel is automatically replaced.

Specular Color, Intensity and Exponent define the classic built-in specular highlight. Intensity changes strength while Exponent changes highlight size/hardness; these are not metal/roughness PBR parameters.

Transmittance Attenuation, Alpha Detail, Color Detail and Saturation describe the built-in material's transmitted contribution. Diagnose them under controlled lighting separately from the per-channel replacement modes.

Receives Lighting and Receives Shadows determine how the replacement material participates in 3D lighting and shadows. The checkboxes do not create a light or shadow map by themselves; the scene and Renderer3D still need a valid lighting/shadow setup.

Two Sided makes the material visible from both polygon sides. It is a material-side option, not a repair for bad normals, winding or topology.

ReplaceMaterial3D does not create texture coordinates. If a 2D texture is stretched, mirrored or missing, diagnose source UVs or UVMap3D separately. Material assignment and texture-coordinate generation are different pipeline stages.

The tool also does not repair normals/tangents or change positions/faces. Use ReplaceNormals3D for surface vectors, UVMap3D for mapping coordinates, and Weld3D/Triangulate3D or the source DCC for topology work.

Placement relative to Merge3D depends on scope. Put ReplaceMaterial3D before Merge3D when only one branch should be restyled; put it after Merge3D when Object/Material ID filters need to select geometry inside a combined scene.

The captured project Inspector confirms current Controls for Enable, four Replace Mode dropdowns and the two ID-limit checkboxes. The captured Material tab shows Diffuse, Specular, Transmittance, Receives Lighting/Shadows, Two Sided and MaterialID. Conditional ID fields and exact target-build defaults remain live-verification items.

Renderer3D remains the scene-to-image boundary. ReplaceMaterial3D.Output can feed Merge3D, Transform3D, Override3D, other 3D processors or Renderer3D.Scene; MediaOut and ordinary 2D Merge expect Renderer3D.Image instead.