The new project creation window allows to create a Substance Project to store the 3D mesh and its texturing.

Substance Painter creates a new Texture set per Material definition on the mesh you are importing. This means you can import multiple meshes from a single file with overlapping UVs if you give them different materials.

Creating a new project

To create a new project click on File > New to create a new Substance Painter project.

Below is an explanation of all the parameter available in the New Project window (see the image above) :

Parameter	Description
Template	Allows to specify a template that will define the default settings of the project (Texture Set settings, Shaders, Display settings and Baking settings). Templates are *.spt files that can be created via the file menu and saved inside the Shelf folder to easily share them with team members.
File	Click on the "Select" button to specify a mesh file to load. Mesh files can have the following extension : fbx (Autodesk FBX) abc (Alembic) obj (Wavefront OBJ) dae (Collada) ply (Stanford Triangle Format) gltf (GL Transmission Format)

Create a Texture Set per UDIM tile	Instead of using Material definitions found on the mesh to create Texture Sets, the import process will create a Texture Set per UV range (UDIM Tile). For more information see : UDIM In case the UDIM creation fails, the import process will fallback to the creation of a regular project instead with Texture Sets based on Materials.
Import Cameras	If cameras are present in the mesh file, they will be imported in the project and accessible as preset for visualization. Substance Painter doesn't support some types of cameras : Physical cameras from 3DS Max. Orthographic cameras stored in Alembic files (*.abc).

Document Resolution	Defines the default texture resolution of the project for each Texture Sets. The resolution can go up to 4K (4096x4096 pixels) when working inside the applicaiton and 8K (8192x8192 pixels) when exporting. The resolution can be changed at anytime later on via the Texture Set settings.
Normal Map Format	Defines the Normal map format for the project, can be either DirectX (X+, Y-, Z+) OpenGL (X+, Y+, Z+) As a reminder : Unreal Engine use DirectX by default. Unity use OpenGL by default.
Compute Tangent Space per Fragment	If enabled, the Binormals (or Bitangents) are computed in the fragment (pixel) shader instead of the vertex shader. This parameter impacts the way the Normal map is decoded by the Shader in the viewport. Changing this settings will require to rebake the Normal map. As a reminder : Unreal Engine needs this setting to be Enabled. Unity needs this setting to be Disabled.

Import mesh normal maps and baked maps for all the materials.	Use the "Add" button to loads texture files as Mesh maps and automatically assign them in the Texture Set settings. See below for the naming convention to follow and an example.

Importing Mesh maps

It is possible to import mesh maps (baked texture specific to the mesh) and have them automatically assigned in the Texture Set Settings. To do so a specific naming convention must be followed. Mesh maps can be baked directly in Substance Painter or via Substance Designer .

Naming convention: TextureSetName_MeshMapName

Example: DefaultMaterial_ambient_occlusion.png

Bellow is a list of all the Mesh map names supported:

Mesh map	Filename convention
Ambient occlusion	ambient_occlusion
Curvature	curvature
Normal	normal_base
World Space Normal	world_space_normals
ID	id
Position	position
Thickness	thickness