Here are the main step of the importer:
- Reading and parsing file (See init.py and gltf2_blender_gltf.py files)
- Creating virtual tree and compute nodes (see gltf2_blender_vnode.py file)
- Then Blender objects are created, based on virtual tree nodes (see all create static methods of blender/imp/gltf2_blender_ files)
- For animations, all gltf animations are created, but only the first one is then set as Blender active action.
If you want to add a new material extension, here are some steps you need to follow:
- Add the extension in list of managed extensions, in extensions_managed list of glTFImporter class
- If your extension need a node that is not Principled Shader node, add it, and correspondance links, in make_output_nodes function, in gltf2_blender_pbrMetallicRoughness.py file
- Add your newly created nodes for textures in calc_locations function, in order to have the nodes correcly displayed without overlapping
- Add you new function at end of pbr_metallic_roughness function. Create this function in a new file, on blender/imp/ directory
Here are the main step of the exporter:
- A virtual node tree is created, then filtered (See blender/exp/gltf2_blender_gather_tree.py file)
- Based on this tree, nodes are exported, with some cache, avoiding calculating multiple time the same things
- At end of process, json tabs are created, replacing references to nodes by index in tabs (See multiple traverse functions)
- In gltf2_blender_gather_materials.py/__gather_extensions, add a function to manage your extension
- Create an Extension class to store your extension data.
- Third parameter is used to set the extension required
- If you need an extension at root of json, use ChildOfRootExtension instead
- If your texture is a simple mapping of channels:
- Add your channel mapping in __get_image_data_mapping function
- Example: Clearcoat
- If your texture needs a complex calculation:
- Add a check in __get_image_data function to call your specific function
- In your function, create an ExportImage class, setting a function as numpy calculation, calling the set_calc method
- In this function, store needed data for calculation, by using store_data method
- Create a new file in blender/exp/, storing your numpy calculation function. This function will use data stored in ExportImage class
- Example: Specular
- If your extension manages some texture, make sure to manage active UVMaps checks in gltf2_blender_gather_materials.py/gather_material function