ImporterMesh is a type of [Resource] analogous to [ArrayMesh]. It contains vertex array-based geometry, divided in [i]surfaces[/i]. Each surface contains a completely separate array and a material used to draw it. Design wise, a mesh with multiple surfaces is preferred to a single surface, because objects created in 3D editing software commonly contain multiple materials.
Unlike its runtime counterpart, [ImporterMesh] contains mesh data before various import steps, such as lod and shadow mesh generation, have taken place. Modify surface data by calling [method clear], followed by [method add_surface] for each surface.
Creates a new surface. [method Mesh.get_surface_count] will become the [code]surf_idx[/code] for this new surface.
Surfaces are created to be rendered using a [param primitive], which may be any of the values defined in [enum Mesh.PrimitiveType].
The [param arrays] argument is an array of arrays. Each of the [constant Mesh.ARRAY_MAX] elements contains an array with some of the mesh data for this surface as described by the corresponding member of [enum Mesh.ArrayType] or [code]null[/code] if it is not used by the surface. For example, [code]arrays[0][/code] is the array of vertices. That first vertex sub-array is always required; the others are optional. Adding an index array puts this surface into "index mode" where the vertex and other arrays become the sources of data and the index array defines the vertex order. All sub-arrays must have the same length as the vertex array (or be an exact multiple of the vertex array's length, when multiple elements of a sub-array correspond to a single vertex) or be empty, except for [constant Mesh.ARRAY_INDEX] if it is used.
The [param blend_shapes] argument is an array of vertex data for each blend shape. Each element is an array of the same structure as [param arrays], but [constant Mesh.ARRAY_VERTEX], [constant Mesh.ARRAY_NORMAL], and [constant Mesh.ARRAY_TANGENT] are set if and only if they are set in [param arrays] and all other entries are [code]null[/code].
The [param lods] argument is a dictionary with [float] keys and [PackedInt32Array] values. Each entry in the dictionary represents an LOD level of the surface, where the value is the [constant Mesh.ARRAY_INDEX] array to use for the LOD level and the key is roughly proportional to the distance at which the LOD stats being used. I.e., increasing the key of an LOD also increases the distance that the objects has to be from the camera before the LOD is used.
The [param flags] argument is the bitwise or of, as required: One value of [enum Mesh.ArrayCustomFormat] left shifted by [code]ARRAY_FORMAT_CUSTOMn_SHIFT[/code] for each custom channel in use, [constant Mesh.ARRAY_FLAG_USE_DYNAMIC_UPDATE], [constant Mesh.ARRAY_FLAG_USE_8_BONE_WEIGHTS], or [constant Mesh.ARRAY_FLAG_USES_EMPTY_VERTEX_ARRAY].
[b]Note:[/b] When using indices, it is recommended to only use points, lines, or triangles.
[param normal_merge_angle] and [param normal_split_angle] are in degrees and used in the same way as the importer settings in [code]lods[/code]. As a good default, use 25 and 60 respectively.
The number of generated lods can be accessed using [method get_surface_lod_count], and each LOD is available in [method get_surface_lod_size] and [method get_surface_lod_indices].
[param bone_transform_array] is an [Array] which can be either empty or contain [Transform3D]s which, for each of the mesh's bone IDs, will apply mesh skinning when generating the LOD mesh variations. This is usually used to account for discrepancies in scale between the mesh itself and its skinning data.
