I tried various hacks in order to make it work, though is mostly based on experience and pure luck, I was just about to abandon this effort. 
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get_selection_point is a straight copy from the template code, I didn’t double checked it at all.
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The id name bl_idname = "object.test_asset_library_place_object" is changed to object just to make it sure that the operator will run on the OBJECT context. Though perhaps you would possibly introduce your own operator namespace as originally you intended, though you will have to create a poll method and lock the operator on the OBJECT context mode again. My estimation on this is that the operator can either be invoked from the panel context or the object context but at least you will have to discard the panel context for good, once you leave the panel area you enter the view3D area and then the operator is invoked on the OBJECT context (thus you get the region_data for 3D region). But either way if you consider that it does not worth the trouble of trying it just stick to OBJECT context for good.
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While on the panel, when the operator is invoked drag_operator="object.test_asset_library_place_object('INVOKE_DEFAULT')", the INVOKE_DEFAULT parameter can be thrown as well, is a common idiom used often. In this case you will be able to override completely the context from where it operator is invoked (the sidepanel) and thus the modal operator will use it’s own predefined one (as in bl_idname).
P.S. If any of my interpretations are wrong or anyone has some comments on them, can mention anything needed for better clarification.
import bpy
import os
from bpy_extras import view3d_utils
from bpy.app.handlers import persistent
from bpy.types import (
Operator,
Panel,
PropertyGroup,
UIList,
AddonPreferences,
)
from bpy.props import (
IntProperty,
PointerProperty,
CollectionProperty,
)
bl_info = {
"name": "Test Asset Library",
"author": "Andrew Peel",
"version": (0, 0, 1),
"blender": (3, 0, 0),
"location": "3D Viewport Sidebar",
"description": "Test Asset Library",
"warning": "",
"wiki_url": "",
"category": "Asset Library",
}
@persistent
def load_library(dummy):
"""
Load Asset Libraries
"""
LIBRARY_NAME = "test_library"
LIBRARY_PATH = os.path.join(os.path.dirname(__file__),'assets')
prefs = bpy.context.preferences
asset_lib = prefs.filepaths.asset_libraries.get(LIBRARY_NAME)
if not asset_lib:
bpy.ops.preferences.asset_library_add()
asset_lib = prefs.filepaths.asset_libraries[-1]
asset_lib.name = LIBRARY_NAME
asset_lib.path = str(LIBRARY_PATH)
for workspace in bpy.data.workspaces:
workspace.asset_library_ref = LIBRARY_NAME
def get_selection_point(context, event):
"""Run this function on left mouse, execute the ray cast"""
# get the context arguments
scene = context.scene
region = context.region
rv3d = context.region_data
coord = event.mouse_region_x, event.mouse_region_y
# get the ray from the viewport and mouse
view_vector = view3d_utils.region_2d_to_vector_3d(region, rv3d, coord)
ray_origin = view3d_utils.region_2d_to_origin_3d(region, rv3d, coord)
ray_target = ray_origin + view_vector
def visible_objects_and_duplis():
"""Loop over (object, matrix) pairs (mesh only)"""
depsgraph = context.evaluated_depsgraph_get()
for dup in depsgraph.object_instances:
if dup.is_instance: # Real dupli instance
obj = dup.instance_object
yield (obj, dup.matrix_world.copy())
else: # Usual object
obj = dup.object
yield (obj, obj.matrix_world.copy())
def obj_ray_cast(obj, matrix):
"""Wrapper for ray casting that moves the ray into object space"""
# get the ray relative to the object
matrix_inv = matrix.inverted()
ray_origin_obj = matrix_inv @ ray_origin
ray_target_obj = matrix_inv @ ray_target
ray_direction_obj = ray_target_obj - ray_origin_obj
# cast the ray
success, location, normal, face_index = obj.ray_cast(ray_origin_obj, ray_direction_obj)
if success:
return location, normal, face_index
else:
return None, None, None
# cast rays and find the closest object
best_length_squared = -1.0
best_obj = None
for obj, matrix in visible_objects_and_duplis():
if obj.type == 'MESH':
hit, normal, face_index = obj_ray_cast(obj, matrix)
if hit is not None:
hit_world = matrix @ hit
scene.cursor.location = hit_world
length_squared = (hit_world - ray_origin).length_squared
if best_obj is None or length_squared < best_length_squared:
best_length_squared = length_squared
best_obj = obj
# now we have the object under the mouse cursor,
# we could do lots of stuff but for the example just select.
if best_obj is not None:
# for selection etc. we need the original object,
# evaluated objects are not in viewlayer
best_original = best_obj.original
best_original.select_set(True)
context.view_layer.objects.active = best_original
class test_library_OT_place_object(bpy.types.Operator):
bl_idname = "object.test_asset_library_place_object"
bl_label = "Place Object"
bl_decription = "Test operator to define custom placement functionality"
bl_options = {'UNDO'}
obj = None
def execute(self, context):
# TRIED TO GET 3D REGION DATA, BUT RETURNS WRONG VIEW MATRIX
# for area in context.screen.areas:
# if area.type == 'VIEW_3D':
# for region in area.regions:
# if region.data:
# self.region_data = region.data
self.get_object(context.region_data)
context.window_manager.modal_handler_add(self)
context.area.tag_redraw()
return {'RUNNING_MODAL'}
def get_object(self,context):
object_file_path = os.path.join(os.path.dirname(__file__),'assets','library.blend')
with bpy.data.libraries.load(object_file_path) as (data_from, data_to):
data_to.objects = data_from.objects
for obj in data_to.objects:
self.obj = obj
context.view_layer.active_layer_collection.collection.objects.link(obj)
def modal(self, context, event):
context.view_layer.update()
selected_point, selected_obj, selected_normal = get_selection_point(context, event)
self.obj.location = selected_point
if event.type == 'LEFTMOUSE' and event.value == 'PRESS':
return {'FINISHED'}
if event.type in {'RIGHTMOUSE', 'ESC'}:
return {'CANCELLED'}
if event.type in {'MIDDLEMOUSE', 'WHEELUPMOUSE', 'WHEELDOWNMOUSE'}:
return {'PASS_THROUGH'}
return {'RUNNING_MODAL'}
class TEST_LIBRARY_PT_library(bpy.types.Panel):
bl_space_type = 'VIEW_3D'
bl_region_type = 'UI'
bl_label = "Test Library"
bl_category = "Test Library"
def draw(self, context):
layout = self.layout
workspace = context.workspace
wm = context.window_manager
layout.prop(workspace,'asset_library_ref')
activate_op_props, drag_op_props = layout.template_asset_view(
"test_library",
workspace,
"asset_library_ref",
wm.test_library,
"library_assets",
workspace.test_library,
"library_index",
filter_id_types={"filter_object"},
display_options={'NO_FILTER','NO_LIBRARY'},
# activate_operator="object.test_asset_library_place_object",
drag_operator="object.test_asset_library_place_object('INVOKE_DEFAULT')",
)
class Test_Library_Workspace_Props(PropertyGroup):
library_index: IntProperty()
@classmethod
def register(cls):
bpy.types.WorkSpace.test_library = PointerProperty(
name="Home Builder Props",
description="Home Builder Props",
type=cls,
)
@classmethod
def unregister(cls):
del bpy.types.WorkSpace.test_library
class Test_Library_Window_Manager_Props(PropertyGroup):
library_assets: CollectionProperty(type=bpy.types.AssetHandle)
@classmethod
def register(cls):
bpy.types.WindowManager.test_library = PointerProperty(
name="Home Builder Props",
description="Home Builder Props",
type=cls,
)
@classmethod
def unregister(cls):
del bpy.types.WindowManager.test_library
def register():
bpy.utils.register_class(Test_Library_Window_Manager_Props)
bpy.utils.register_class(Test_Library_Workspace_Props)
bpy.utils.register_class(TEST_LIBRARY_PT_library)
bpy.utils.register_class(test_library_OT_place_object)
bpy.app.handlers.load_post.append(load_library)
def unregister():
bpy.utils.unregister_class(Test_Library_Window_Manager_Props)
bpy.utils.unregister_class(Test_Library_Workspace_Props)
bpy.utils.unregister_class(TEST_LIBRARY_PT_library)
bpy.utils.unregister_class(test_library_OT_place_object)
bpy.app.handlers.load_post.remove(load_library)
if __name__ == '__main__':
print('register')
load_library(None)
register()