Replacing Meshes - enimaroah/SB3Utility GitHub Wiki

One of the most important functions for modding games is the replacement of meshes. Depending on the 3d editor used there are obstacles to take. Not every file format available for exchange can transport all required information. The replacement function in Sb3UGS can help to fill such gaps by using existing information from the mesh already present.

The focus here is on skinned meshes. A skinned mesh is deformed in the game depending on the movements (usually rotation) of bones. Example: you model a whole arm in one piece (one submesh), but want it to be able to bent at the elbow, hand and fingers. Whereever a mesh bends one bone ends and another begins. Therefore other programs like Maya let you handle joints, and indeed bones in Sb3UGS are inaccurately named.

Seen from the perspective of the bone: vertices follow the movement of upto four bones. How much they follow a specific bone is defined by a weight for that bone. And as just said, the vertex can store four weights.

All used bones are collected in a list which is attached to the mesh, the bonelist. This bonelist has two aspects. For one, it names all frames of the skeleton which are used as bones. The second aspect is stored as a matrix which defines a translation, rotation and scaling. This matrix can be computed from the frame's matrix. And if all used bone's matrices were computed then you would see the mesh in its Rest Pose, sometimes called Bind Pose. If a bone matrix would always be computed, then it would not have to be stored and transported separately. Storing this matrix with an offset leads indeed to a modified pose. This offset pose is added to all applied animations!

The first option in the replacement dialog is the target parent frame. In this frame should already exist a mesh, the destination mesh. The new mesh from the workspace will be filled with game specific information from the destination mesh.

The Replace method will replace any existing bonelist - none of the bones of the destination mesh will be present in the result. With this method no submesh of the destination mesh will be present in the result, regardless of replacement options of the submesh in the workspace.

Merge will retain all destination bones and merge the bones from the imported mesh to the result. The destination submeshes will remain in the result, except when they are replaced from imported submeshes with checked Replace Original Submesh option.

The imported mesh may not contain normals, tangents or bone weights (MQO files). The Normals and Bones option are changed to Copy Nearest. Replace would copy normals, tangents and bone information along with the vertex position. So Replace can only be used if you have that information in the imported file (FBX). Copy In Order copies the information like Nearest, but not based on the distance of vertices, but instead just one by one, from the first destination vertex to the first imported, second to second, and so on. Use this mode after morphing meshes!

The bottom option Nearest either limits the search for nearest vertices to the destination submesh or expands the search to all submeshes. The latter can be very slow and unnecessary, if the imported submesh and its destination submesh are very close to each other and cover the same or nearly the same space in 3d.