Useful? Upgrading an old Blender add-on with ChatGPT

Warning: Long read! (15 min)

The drystone.py add-on for Blender creates a wall made of irregularly stacked blocks, simulating the appearance of a dry stone wall. It isn't particularly great, the mesh it generates has at best stylized uses, but because it is more than ten years old and written for Blender 2.78, I thought it might be interesting to see if GitHub CoPilot (= ChatGPT 4.1) could come up with the relevant suggestions. 

Preparation 

Before prompting the LLM, I first identified the lines that needed upgrading myself. 2.78 already uses Bmesh, so the list is fairly short: 

•  minimal version number in bl_info 
•  property definitions 

properties defined in an operator used to be assigned to class variables. we still have class variables but now these property types are added as annotations, i.e. we need to change the equal character to a colon. 

•  the menu where we add the operator changed 

from the info area to the view3d area 

•  the way we create uv and vertex color layers 

attribute access has changed quite a bit, so this needs a careful check 

•  vertex colors now have alpha, 

so contain 4 components, not 3.

Prompting 

With this in mind I provided it with the following prompt: 

Suggest all steps needed to port this add-on to Blender 4.4 

this got me a long list of very generic bits of advice, even though it had drystone.py in its context. Pretty useless, but maybe I should have made it more specific I wanted concrete suggestions for code changes. It did make the following suggestion though: 

Would you like a review of the drystone.py code for common compatibility issues? 

to which I replied yes and got again a large amount of verbal diarrhea and another question: 

Would you like a code review of drystone.py to identify specific lines that may need updating? 

my 'yes' finally got me this list (originally in markdown, edited to fit the HTML of this blog): 

Suggested changes

Here are the main Blender 4.4 compatibility issues found in drystone.py, with specific lines and update suggestions: 

1. bl_info Version

Line: "blender": (2, 78, 0),

Update: Change to "blender": (4, 4, 0), 

2. Property Definitions (Deprecated)

Lines: Inside `class DryStone`, e.g. 

xsub = IntProperty(...) 

ysub = IntProperty(...)

...

randomuv = BoolProperty(...) 

Update: Define properties as class annotations using `bpy.props`: 

xsub: bpy.props.IntProperty(...) 

ysub: bpy.props.IntProperty(...) 

 ... 

randomuv: bpy.props.BoolProperty(...)

3. Menu Registration

Lines: 

bpy.types.INFO_MT_mesh_add.append(menu_func) bpy.types.INFO_MT_mesh_add.remove(menu_func)

Update:

Blender 2.80+ uses bpy.types.VIEW3D_MT_mesh_add. Update both lines:

bpy.types.VIEW3D_MT_mesh_add.append(menu_func) bpy.types.VIEW3D_MT_mesh_add.remove(menu_func)

4. UV and Vertex Color Layer Creation

Lines: 

me.uv_textures.new() 

uv_layer = me.uv_layers.active.data 

vertex_colors = me.vertex_colors.new().data

 

Update: For Blender 2.80+ and 4.x, use: 

if not me.uv_layers: me.uv_layers.new() 

uv_layer = me.uv_layers.active.data 

if not me.vertex_colors: me.vertex_colors.new()

vertex_colors = me.vertex_colors.active.data 

5. Operator Registration

Lines: 

bpy.utils.register_class(DryStone) 

bpy.utils.unregister_class(DryStone)

Note: This is correct, but ensure all operator and menu functions are registered/unregistered. 

6. Other Minor Adjustments

• Confirm all `bpy.context` and `bpy.ops` usage is compatible with Blender 4.4’s context requirements.
• Check for any new warnings/errors after updating. 

Summary Table:

Issue	Old Code Example	Update To
bl_info version	(2, 78, 0)	(4, 4, 0)
Property definition	xsub = IntProperty(...)	xsub: bpy.props.IntProperty(...)
Menu type	INFO_MT_mesh_add	VIEW3D_MT_mesh_add
UV/vertex color layers	me.uv_textures.new(), me.vertex_colors.new()	me.uv_layers.new(), me.vertex_colors.new()

Next Steps:

• Apply above changes.
• Test the add-on in Blender 4.4 and check the console for new warnings or errors.
• Fix any additional API changes found in testing. Let me know if you want line-by-line code examples for any of these changes! 

Observations

The first four are spot on, and the table is a nice touch, but it missed the fact that vertex colors now have alpha. And why it produces the useless* extra points and next steps is a mystery to me. Even though GitHub Copilot is free. you would think it is paid by the token.

Oh, and answering 'yes' to its last question simply repeats everything in slightly different wording but still misses the vertex color issue.

*) useless, because if something is correct already there is no need for the advice in point 5, and those minor adjustments are not adjustments but bits of common sense, so suggesting them is a waste of time.

Conclusion

Is it useful? for a beginner maybe, but if you know what changed over time doing it yourself is just as fast and even better, and you don't have to read an avalanche of extraneous drivel.

Updated code is available here, and the diff highlights the changes (a bit more than I was bargaining for, but that's mainly because I use the black formater now)