Appendix A - Content Spec Checklist

General

• Unit: cm.
• Maya coordinate system: Y up.
• Models' front direction: +Z in Maya ( -Y in 3ds Max).
• Models should be at the proper position relative to the origin (0,0,0).

Naming

• Each name must be unique, no duplicate names. Names must start with an alphabet letter and contain only alphanumeric and underscore characters.
• Keep name length within 128 characters.
• Use meaningful and descriptive names as possible.

Mesh

• The less meshes for a model the better. Make it a single mesh model if possible.
• No more than 100,000 triangles in a mesh.
• Use faces conservatively. Meshes are for the the overall shape and silhouette, use normal maps for surface details.
• Distribute meshes evenly unless there are special requirements (e.g, a close-up shot).
• Use only triangles or quads. Polygons with more than 4 edges can cause problems in conversion.
• Mesh scales must be (1,1,1). Execute "freeze transform" on meshes.
• Always delete histories except skin clusters and blend shapes. (non-deformer history)
• The minimum size of meshes with blend shapes can't be smaller than 3 cm.
• Each target shape must have an unique name in a skeletal asset, no matter how many Blend Shape Deformers this asset contains.

UV

• Meshes must contain UV sets.
• All static meshes must have light map UVs. It's usually in the 2nd UV set and must be in 0~1 UV space and without any overlapping.

Material

• Apply as few materials to a mesh as possible. Using a mask to separate different surfaces is better.
• Maya Stingray PBS shaders are suggested. Textures must follow PBR rules.
• Texture dimensions should be square powers of two.
• Texture dimensions should not excede 4096x4096.
• Check if all texture files exist.
• The maximum texture number that can be used on a single shader is 16.

Static Asset

• Contains at least one mesh.
• The transformations of static asset nodes must be reset.
• The Local Rotate/Scale Pivot of static asset nodes must be set to (0,0,0).

Skeletal Asset

• The transformations of the "Main" node must be reset.
• The Local Rotate/Scale Pivot of the "Main" node must be set to (0,0,0).
• The bind skeleton must include only joints in the hierarchy.
• All joints must be under one root joint.
• Scales of the "Main" node, joints and ikHandles must be (1,1,1).
• Use joints conservatively (UE4 supports up to 65536 joints).
• The top structure of a rig must follow the spec. It is generated with the "Skeletal Asset" tool.
• Contains at least one mesh.
• Apply smooth bind. Rigid skin is not supported by UE4.
• Meshes can only be skinned to joints under the BindSystem.
• Maximun of 8 bone weights per vertex. PhysX cloth supports 4 at most.
• “Segment Scale Compensate” must be on in all nodes under the “Bind System” group.
• Each mesh can only have one blend shape node applied.
• In-between blend shapes are not supported.

Collective Asset

• Only static assets can be included in a collective asset.