blenderings/retopo_tools/tool.py

import bpy
from bpy.types import Context, Object, Mesh, Scene

def assert_mirror_modifier(obj: Object, target: Object = None):
    modifier = next((modifier for modifier in obj.modifiers if modifier.type == "MIRROR"), None)
    if modifier is None:
        modifier = obj.modifiers.new("Mirror", "MIRROR")
    modifier.use_clip = True

    if target is not None and modifier.mirror_object is None:
        modifier.mirror_object = target
    

def assert_shrinkwrap_modifier(obj: Object, target: Object = None):
    modifier = next((modifier for modifier in obj.modifiers if modifier.type == "SHRINKWRAP"), None)
    if modifier is None:
        modifier = obj.modifiers.new("Shrinkwrap", "SHRINKWRAP")
    
    modifier.show_viewport = False
    modifier.wrap_method = "PROJECT"
    modifier.wrap_mode = "ABOVE_SURFACE"
    modifier.project_limit = 0.0
    modifier.use_negative_direction = True
    modifier.use_positive_direction = True

    
    vgroup = next((group for group in obj.vertex_groups if "no_shrinkwrap" in group.name), None)
    if vgroup is None:
        vgroup = obj.vertex_groups.new(name="no_shrinkwrap")


    modifier.vertex_group = vgroup.name
    modifier.invert_vertex_group = True

    if target is not None and modifier.target is None:
        modifier.target = target


        
def assert_retopo_modifiers(ctx: Context, target: Object = None):
    active = ctx.active_object
    assert_mirror_modifier(active, target)
    assert_shrinkwrap_modifier(active, target)

def setup_project_snap_settings(scene: Scene):
    scene.tool_settings.use_snap = True
    scene.tool_settings.snap_elements = {"FACE"}
    scene.tool_settings.use_snap_self = True
    scene.tool_settings.use_snap_edit = True
    scene.tool_settings.use_snap_nonedit = True
    scene.tool_settings.use_snap_selectable = True
    scene.tool_settings.use_snap_align_rotation = False
    scene.tool_settings.use_snap_backface_culling = True
    scene.tool_settings.use_snap_project = True
    scene.tool_settings.use_snap_translate = True
    scene.tool_settings.use_snap_rotate = True
    scene.tool_settings.use_snap_scale = True

def setup_vertex_snap_settings(scene: Scene):
    scene.tool_settings.use_snap = True
    scene.tool_settings.snap_elements = {"VERTEX"}
    scene.tool_settings.use_snap_self = True
    scene.tool_settings.use_snap_edit = True
    scene.tool_settings.use_snap_nonedit = False
    scene.tool_settings.use_snap_selectable = True
    scene.tool_settings.use_snap_align_rotation = False
    scene.tool_settings.use_snap_backface_culling = True
    scene.tool_settings.use_snap_translate = True
    scene.tool_settings.use_snap_rotate = True
    scene.tool_settings.use_snap_scale = True

def get_context_target(ctx: Context):
    if len(ctx.selected_objects) != 2:
        return None
    return next(obj for obj in ctx.selected_objects if obj is not ctx.active_object)

class RetopoProjectModeOperator(bpy.types.Operator):
    bl_idname = "object.retopoprojectmode"
    bl_label = "RetopoProjectMode"
    bl_options = {"REGISTER", "UNDO"}

    @classmethod
    def poll(Cls, context: Context):
        return context.active_object is not None and type(context.active_object.data) is Mesh

    def execute(self, context: Context):
        bpy.ops.object.mode_set(mode="EDIT")
        target = get_context_target(context)
        assert_retopo_modifiers(context, target)
        setup_project_snap_settings(context.scene)
        self.report({"INFO"}, "Project Mode")
        return {'FINISHED'}


class RetopoVertexModeOperator(bpy.types.Operator):
    bl_idname = "object.retopovertexmode"
    bl_label = "RetopoVertexMode"

    def execute(self, context):
        bpy.ops.object.mode_set(mode="EDIT")
        target = get_context_target(context)
        assert_retopo_modifiers(context, target)
        setup_vertex_snap_settings(context.scene)
        self.report({"INFO"}, "Vertex Mode")
        return {'FINISHED'}