Update technical doc

README.md

@@ -12,10 +12,10 @@ Documentation
 | dev     | https://docs.blender.org/manual/en/dev/addons/import_export/scene_gltf2.html  |
 
 Notes:
-* 3.1 is the current stable release. Check the `blender-v3.1-release` branch.
-* 2.80 - 3.0 are previous stable releases.
+* 3.2 is the current stable release. Check the `blender-v3.2-release` branch.
+* 2.80 - 3.1 are previous stable releases.
 * 2.93 is the current Blender LTS release. Check the `blender-v2.93-release` branch.
-* 3.2 will be the next release. Check the `blender-v3.2-release` branch.
+* 3.3 will be the next release. 
 * master branch of this addon is mirrored in [Blender Addons master](https://developer.blender.org/diffusion/BA/browse/master/io_scene_gltf2/), that will become Blender 3.3.
 
 ### Legacy 2.79 Support
@@ -81,3 +81,8 @@ To run the tests locally, your system should have a `blender` executable in the
 The latest version of [Yarn](https://yarnpkg.com/en/) should also be installed.
 
 Then, in the `tests` folder of this repository, run `yarn install`, followed by `yarn run test`.
+
+Some Technical documentation
+----------------------------
+
+Want to fix some bugs or add some enhancement? You will find some technical overview of this addon [here](Technical.md)

Technical.md

@@ -0,0 +1,45 @@
+# Technical overview
+
+## Importer
+
+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.
+
+### Adding a new material extension
+
+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
+
+
+## Exporter
+
+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)
+
+### Adding a new material extension
+
+- 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