auto_walk/OP_setup_curve_path.py

import bpy, re
from . import fn

## step 1 : Create the curve and/or follow path constraint, snap to ground


def create_follow_path_constraint(ob, curve):
    pref = fn.get_addon_prefs()
    bone_name = pref.tgt_bone
    root = ob.pose.bones.get(bone_name)
    if not root:
        return ('ERROR', f'posebone {bone_name} not found in armature {ob.name} check addon preferences to change name')

    # Clear bone follow path constraint 
    exiting_fp_constraints = [c for c in root.constraints if c.type == 'FOLLOW_PATH']
    for c in exiting_fp_constraints:
        root.constraints.remove(c)

    # loc = ob.matrix_world @ root.matrix.to_translation()
    if root.name == 'root' and root.location != (0,0,0):
        old_loc = root.location
        root.location = (0,0,0)
        print(f'root moved from {old_loc} to (0,0,0) to counter curve offset')

    const = root.constraints.new('FOLLOW_PATH')
    const.target = curve
    # axis only in this case, should be in addon to prefs
    const.forward_axis = 'FORWARD_X'
    const.use_curve_follow = True
    return curve, const

def snap_curve():
    obj = bpy.context.object

    curve = const = None
    if obj.type == 'ARMATURE':
        curve, const = fn.get_follow_curve_from_armature(obj)
    
    to_follow = bpy.context.scene.anim_cycle_settings.path_to_follow
    if not curve and not to_follow:
        return ('ERROR', f'No curve pointed by "Path" filed')

    # get curve from field
    if not curve:
        curve, const = create_follow_path_constraint(obj, to_follow)
        if not curve:
            return (curve, const) # those are error message

    # if obj.type == 'CURVE':
    #     return ('ERROR', f'Select the armature related to curve {obj.name}')
    # else:
    #     return ('ERROR', 'Not an armature object')

    gnd = fn.get_gnd()
    if not gnd:
        return
    
    # if it's on a snap curve, fetch original
    if '_snap' in curve.name:
        org_name = re.sub(r'_snap\.?\d{0,3}$', '', curve.name)
        org_curve = bpy.context.scene.objects.get(org_name)
        if org_curve:
            const.target = org_curve

        # delete old snap
        bpy.data.objects.remove(curve)
        # assign old curve as main one
        curve = org_curve

    nc = curve.copy()
    name = re.sub(r'\.\d{3}$', '', curve.name) + '_snap'
    const.target = nc
    nc.name = name
    nc.data = curve.data.copy()
    nc.data.name = name + '_data'

    curve.users_collection[0].objects.link(nc)

    ## If object mode is Curve subdivide it (TODO if nurbs needs conversion)
    #-# subdivide the curve (if curve is not nurbs)

    # bpy.ops.object.mode_set(mode='EDIT')
    # bpy.ops.curve.select_all(action='SELECT')
    # bpy.ops.curve.subdivide(number_cuts=4)
    # bpy.ops.object.mode_set(mode='OBJECT')

    # shrinkwrap or cast on ground
    mod = nc.modifiers.new('Shrinkwrap', 'SHRINKWRAP')
    mod.wrap_method = 'TARGET_PROJECT'
    mod.target = gnd
    
    # Apply and decimate
    bpy.ops.object.modifier_apply({'object': nc}, modifier="Shrinkwrap", report=False)
    bpy.context.scene.anim_cycle_settings.path_to_follow = nc
    # return 0, nc

class UAC_OT_create_curve_path(bpy.types.Operator):
    bl_idname = "anim.create_curve_path"
    bl_label = "Create Curve"
    bl_description = "Create curve and add follow path constraint"
    bl_options = {"REGISTER", "UNDO"}

    @classmethod
    def poll(cls, context):
        return context.object and context.object.type == 'ARMATURE'

    def execute(self, context):
        # use root (or other specified bone) to find where to put the curve
        pref = fn.get_addon_prefs()
        ob = context.object
        bpy.ops.object.mode_set(mode='OBJECT', toggle=False)
        bone_name = pref.tgt_bone
        root = ob.pose.bones.get(bone_name)
        if not root:
            self.report({'ERROR'}, f'posebone {bone_name} not found in armature {ob.name} check addon preferences to change name')
            return {"CANCELLED"}

        loc = ob.matrix_world @ root.matrix.to_translation()

        # TODO propose nurbs instead of curve
        # TODO mode elegantly create the curve using data...
        bpy.ops.curve.primitive_bezier_curve_add(radius=1, enter_editmode=True, align='WORLD', location=loc, scale=(1, 1, 1))
        # fast straighten
        print('context.object: ', context.object.name)
        curve = context.object
        curve.name = 'curve_path'
        curve.show_in_front = True
        bpy.ops.curve.handle_type_set(type='VECTOR')
        bpy.ops.curve.handle_type_set(type='ALIGNED')
        # offset to have start      
        bpy.ops.transform.translate(value=(1, 0, 0), orient_type='LOCAL', 
        orient_matrix=((1, 0, 0), (0, 1, 0), (0, 0, 1)), orient_matrix_type='LOCAL', 
        constraint_axis=(True, False, False), mirror=True, use_proportional_edit=False)
        
        context.space_data.overlay.show_curve_normals = True
        context.space_data.overlay.normals_length = 0.2

        context.scene.anim_cycle_settings.path_to_follow = curve
        ## back to objct mode ?
        # bpy.ops.object.mode_set(mode='OBJECT', toggle=False)
        
        ## TODO replace this part with >> create_follow_path_constraint(ob, curve)

        if root.name == 'root' and root.location != (0,0,0):
            old_loc = root.location
            root.location = (0,0,0)
            print(f'root moved from {old_loc} to (0,0,0) to counter curve offset')

        # make follow path constraint
        const = root.constraints.new('FOLLOW_PATH')
        const.target = curve
        # axis only in this case, should be in addon to prefs
        const.forward_axis = 'FORWARD_X' # 'TRACK_NEGATIVE_Y' 
        const.use_curve_follow = True

        return {"FINISHED"}


class UAC_OT_create_follow_path(bpy.types.Operator):
    bl_idname = "anim.create_follow_path"
    bl_label = "Create follow path constraint"
    bl_description = "Create follow path targeting curve in field"
    bl_options = {"REGISTER", "UNDO"}

    @classmethod
    def poll(cls, context):
        return context.object and context.object.type == 'ARMATURE'

    def execute(self, context):
        ob = context.object
        curve = context.scene.anim_cycle_settings.path_to_follow
        create_follow_path_constraint(ob, curve)

        return {"FINISHED"}

class UAC_OT_snap_curve_to_ground(bpy.types.Operator):
    bl_idname = "anim.snap_curve_to_ground"
    bl_label = "snap_curve_to_ground"
    bl_description = "snap curve"
    bl_options = {"REGISTER", "UNDO"}

    @classmethod
    def poll(cls, context):
        return context.object and context.object.type == 'ARMATURE'

    def execute(self, context):
        err = snap_curve()
        if err:
            self.report({err[0]}, err[1])
            if err[0] == 'ERROR':
                return {"CANCELLED"}
        return {"FINISHED"}

classes=(
UAC_OT_create_curve_path,
UAC_OT_create_follow_path,
UAC_OT_snap_curve_to_ground,
)

def register():
    for cls in classes:
        bpy.utils.register_class(cls)

def unregister():
    for cls in reversed(classes):
        bpy.utils.unregister_class(cls)

# if __name__ == "__main__":
#     register()