Actor Merging

The Merge Actors tool enables the user to combine multiple Static Meshes into a single new Actor. Materials can also be baked together into a single Material with a series of custom textures using a new UV layout, and the original Static Meshes used can even be completely replaced by the newly merged asset.

The Merge Actor feature is officially supported in 4.12 and later. In 4.8 to 4.11, it must be activated from the Editor Settings under the Experimental tab. If you are using a version of the engine earlier than 4.12, this feature is considered experimental and is not officially supported.


Actor Merging Worklow

Merging Static Meshes in your scene is handled like so:

  1. Select a number of Static Meshes in your level that your would like to merge.

  2. From the main menubar choose Window > Developer Tools > Merge Actors.

  3. Choose the appropriate options (explained below).

  4. Click the Merge Actors button.

If you select fewer than two Static Meshes, you will get a warning saying there are insufficient meshes to merge.

Merge Actors Tool Options

At the top of the Merge Actors window is a list of all the Static Meshes selected in the viewport. Here you can check which meshes will be included in the final merge.

If you have one or fewer meshes selected, you will see a yellow warning near the bottom of the window stating that you have insufficient mesh components for merging.

Option Description

Mesh Components List

This area contains a checklist where you can chose which of the selected meshes will be included in the merge.

Mesh Settings

Pivot Point at Zero If set to true, the pivot point of the final merged actor will be set to the scene's origin <0,0,0>. If set to false, the pivot will be located at the pivot location of the first Static Mesh Actor selected for the merge.
Merge Physics Data If true, this will merge together all of the physics primitives into a single physics object.
Bake Vertex Data Bakes vertex data including vertex color and normals into the new resulting mesh.
LOD Selection Type Use this to control which LODs are added to the merged object.

Advanced Options

These options are found by expanding the small white triangle icon in the middle of the options list
Generate Lightmap UVs Creates a new lightmap UV layout for the merged mesh, using the existing UV islands. This new layout will be placed in the Target Light Map UVChannel.
Target Light Map UVChannel Specifies the UV channel into which the new lightmap UVs will be saved.
Target Light Map Resolution Specifies the resolution for the new lightmap UVs, which controls the distance calculated between each island within the layout. Higher resolutions will yield tighter spacing between each island.

Material Settings

Merge Materials If checked, the Materials of all the merged assets will be combined into a single Material with new UV layout. The following subsettings apply only if Merge Materials is checked.
Texture Size This provides access to the X and Y pixel dimensions (resolution) for the final merged Material's textures.
Texture Sizing Type The settings for this property are explained in the table below.
Normal Map If checked, a Normal map will be baked out for the resulting merged Actor.
Metallic Map If checked, a Metallic map will be baked out for the resulting merged Actor. This nullifies the Metallic Constant property.
Metallic Constant Only enabled if Metallic Map is unchecked, this sets a constant value for the Metallic property of the resulting merged Actor's Material.
Roughness Map If checked, a Roughness map will be baked out for the resulting merged Actor. This nullifies the Roughness Constant property.
Roughness Constant Only enabled if Roughness Map is unchecked, this sets a constant value for the Roughness property of the resulting merged Actor's Material.
Specular Map If checked, a Specular map will be baked out for the resulting merged Actor. This nullifies the Specular Constant property.
Specular Constant Only enabled if Specular Map is unchecked, this sets a constant value for the Specular property of the resulting merged Actor's Material.
Emissive Map If checked, an Emissive map will be baked out for the resulting merged Actor.
Use Vertex Data for Baking Material Whether or not to use vertex data such as vertex color to bake Material result. Useful if you have a Material that is being controlled in some way by vertex color.

Landscape Culling

Use Landscape Culling If checked, existing landscape geometry will be used to cull fully occluded triangles. For example, if you had a tree mesh that was planted such that the bottommost triangles were well below the surface of a landscape, then those occluded triangles would be removed upon merge.

Standard Options

Replace Source Actors If checked, the Actors selected in the viewport will be removed and replaced with the new merged version. This will not afffect the the original objects in the Content Browser.

Texture Sizing Type Settings

Use TextureSize for all material properties This uses the resolution set in the Texture Size property for all baked textures.
Use automatically biased texture sizes based on TextureSize This creates a 1:0.5:0.25 bias for all textures such that Normal gets 100% of the resolution set in Texture Size, Diffuse (Base Color) gets 50% of Texture Size, and all other properties get 25% of TextureSize
Use per property manually overriden texture sizes This provides individual number entry fields for explicitly providing the resolution for each map being baked.
Use Simplygon's automatic texture sizing This uses Simplygon's algorithm for texture sizing based on its decimation settings. This should only be used if you are already using Simplygon.