Depsgraph(bpy_struct)

Dependency graph: Evaluated ID example

This example demonstrates access to the evaluated ID (such as object, material, etc.) state from an original ID. This is needed every time one needs to access state with animation, constraints, and modifiers taken into account.

import bpy


class OBJECT_OT_evaluated_example(bpy.types.Operator):
    """Access evaluated object state and do something with it"""
    bl_label = "DEG Access Evaluated Object"
    bl_idname = "object.evaluated_example"

    def execute(self, context):
        # This is an original object. Its data does not have any modifiers applied.
        obj = context.object
        if obj is None or obj.type != 'MESH':
            self.report({'INFO'}, "No active mesh object to get info from")
            return {'CANCELLED'}
        # Evaluated object exists within a specific dependency graph.
        # We will request evaluated object from the dependency graph which corresponds to the
        # current scene and view layer.
        #
        # NOTE: This call ensure the dependency graph is fully evaluated. This might be expensive
        # if changes were made made to the scene, but is needed to ensure no dangling or incorrect
        # pointers are exposed.
        depsgraph = context.evaluated_depsgraph_get()
        # Actually request evaluated object.
        #
        # This object has animation and drivers applied on it, together with constraints and
        # modifiers.
        #
        # For mesh objects the object.data will be a mesh with all modifiers applied.
        # This means that in access to vertices or faces after modifier stack happens via fields of
        # object_eval.object.
        #
        # For other types of objects the object_eval.data does not have modifiers applied on it,
        # but has animation applied.
        #
        # NOTE: All ID types have `evaluated_get()`, including materials, node trees, worlds.
        object_eval = obj.evaluated_get(depsgraph)
        mesh_eval = object_eval.data
        self.report({'INFO'}, f"Number of evaluated vertices: {len(mesh_eval.vertices)}")
        return {'FINISHED'}


def register():
    bpy.utils.register_class(OBJECT_OT_evaluated_example)


def unregister():
    bpy.utils.unregister_class(OBJECT_OT_evaluated_example)


if __name__ == "__main__":
    register()

Dependency graph: Original object example

This example demonstrates access to the original ID. Such access is needed to check whether object is selected, or to compare pointers.

import bpy


class OBJECT_OT_original_example(bpy.types.Operator):
    """Access original object and do something with it"""
    bl_label = "DEG Access Original Object"
    bl_idname = "object.original_example"

    def check_object_selected(self, object_eval):
        # Selection depends on a context and is only valid for original objects. This means we need
        # to request the original object from the known evaluated one.
        #
        # NOTE: All ID types have an `original` field.
        obj = object_eval.original
        return obj.select_get()

    def execute(self, context):
        # NOTE: It seems redundant to iterate over original objects to request evaluated ones
        # just to get original back. But we want to keep example as short as possible, but in real
        # world there are cases when evaluated object is coming from a more meaningful source.
        depsgraph = context.evaluated_depsgraph_get()
        for obj in context.editable_objects:
            object_eval = obj.evaluated_get(depsgraph)
            if self.check_object_selected(object_eval):
                self.report({'INFO'}, f"Object is selected: {object_eval.name}")
        return {'FINISHED'}


def register():
    bpy.utils.register_class(OBJECT_OT_original_example)


def unregister():
    bpy.utils.unregister_class(OBJECT_OT_original_example)


if __name__ == "__main__":
    register()

Dependency graph: Iterate over all object instances

Sometimes it is needed to know all the instances with their matrices (for example, when writing an exporter or a custom render engine). This example shows how to access all objects and instances in the scene.

import bpy


class OBJECT_OT_object_instances(bpy.types.Operator):
    """Access original object and do something with it"""
    bl_label = "DEG Iterate Object Instances"
    bl_idname = "object.object_instances"

    def execute(self, context):
        depsgraph = context.evaluated_depsgraph_get()
        for object_instance in depsgraph.object_instances:
            # This is an object which is being instanced.
            obj = object_instance.object
            # `is_instance` denotes whether the object is coming from instances (as an opposite of
            # being an emitting object. )
            if not object_instance.is_instance:
                print(f"Object {obj.name} at {object_instance.matrix_world}")
            else:
                # Instanced will additionally have fields like uv, random_id and others which are
                # specific for instances. See Python API for DepsgraphObjectInstance for details,
                print(f"Instance of {obj.name} at {object_instance.matrix_world}")
        return {'FINISHED'}


def register():
    bpy.utils.register_class(OBJECT_OT_object_instances)


def unregister():
    bpy.utils.unregister_class(OBJECT_OT_object_instances)


if __name__ == "__main__":
    register()

Dependency graph: Object.to_mesh()

Function to get a mesh from any object with geometry. It is typically used by exporters, render engines and tools that need to access the evaluated mesh as displayed in the viewport.

Object.to_mesh() is closely interacting with dependency graph: its behavior depends on whether it is used on original or evaluated object.

When is used on original object, the result mesh is calculated from the object without taking animation or modifiers into account:

• For meshes this is similar to duplicating the source mesh.

• For curves this disables own modifiers, and modifiers of objects used as bevel and taper.

• For metaballs this produces an empty mesh since polygonization is done as a modifier evaluation.

When is used on evaluated object all modifiers are taken into account.

Note

The result mesh is owned by the object. It can be freed by calling object.to_mesh_clear().

Note

The result mesh must be treated as temporary, and can not be referenced from objects in the main database. If the mesh intended to be used in a persistent manner use bpy.data.meshes.new_from_object() instead.

Note

If object does not have geometry (i.e. camera) the functions returns None.

import bpy


class OBJECT_OT_object_to_mesh(bpy.types.Operator):
    """Convert selected object to mesh and show number of vertices"""
    bl_label = "DEG Object to Mesh"
    bl_idname = "object.object_to_mesh"

    def execute(self, context):
        # Access input original object.
        obj = context.object
        if obj is None:
            self.report({'INFO'}, "No active mesh object to convert to mesh")
            return {'CANCELLED'}
        # Avoid annoying None checks later on.
        if obj.type not in {'MESH', 'CURVE', 'SURFACE', 'FONT', 'META'}:
            self.report({'INFO'}, "Object can not be converted to mesh")
            return {'CANCELLED'}
        depsgraph = context.evaluated_depsgraph_get()
        # Invoke to_mesh() for original object.
        mesh_from_orig = obj.to_mesh()
        self.report({'INFO'}, f"{len(mesh_from_orig.vertices)} in new mesh without modifiers.")
        # Remove temporary mesh.
        obj.to_mesh_clear()
        # Invoke to_mesh() for evaluated object.
        object_eval = obj.evaluated_get(depsgraph)
        mesh_from_eval = object_eval.to_mesh()
        self.report({'INFO'}, f"{len(mesh_from_eval.vertices)} in new mesh with modifiers.")
        # Remove temporary mesh.
        object_eval.to_mesh_clear()
        return {'FINISHED'}


def register():
    bpy.utils.register_class(OBJECT_OT_object_to_mesh)


def unregister():
    bpy.utils.unregister_class(OBJECT_OT_object_to_mesh)


if __name__ == "__main__":
    register()

Dependency graph: bpy.data.meshes.new_from_object()

Function to copy a new mesh from any object with geometry. The mesh is added to the main database and can be referenced by objects. Typically used by tools that create new objects or apply modifiers.

When is used on original object, the result mesh is calculated from the object without taking animation or modifiers into account:

• For meshes this is similar to duplicating the source mesh.

• For curves this disables own modifiers, and modifiers of objects used as bevel and taper.

• For metaballs this produces an empty mesh since polygonization is done as a modifier evaluation.

When is used on evaluated object all modifiers are taken into account.

All the references (such as materials) are re-mapped to original. This ensures validity and consistency of the main database.

Note

If object does not have geometry (i.e. camera) the functions returns None.

import bpy


class OBJECT_OT_mesh_from_object(bpy.types.Operator):
    """Convert selected object to mesh and show number of vertices"""
    bl_label = "DEG Mesh From Object"
    bl_idname = "object.mesh_from_object"

    def execute(self, context):
        # Access input original object.
        obj = context.object
        if obj is None:
            self.report({'INFO'}, "No active mesh object to convert to mesh")
            return {'CANCELLED'}
        # Avoid annoying None checks later on.
        if obj.type not in {'MESH', 'CURVE', 'SURFACE', 'FONT', 'META'}:
            self.report({'INFO'}, "Object can not be converted to mesh")
            return {'CANCELLED'}
        depsgraph = context.evaluated_depsgraph_get()
        object_eval = obj.evaluated_get(depsgraph)
        mesh_from_eval = bpy.data.meshes.new_from_object(object_eval)
        self.report({'INFO'}, f"{len(mesh_from_eval.vertices)} in new mesh, and is ready for use!")
        return {'FINISHED'}


def register():
    bpy.utils.register_class(OBJECT_OT_mesh_from_object)


def unregister():
    bpy.utils.unregister_class(OBJECT_OT_mesh_from_object)


if __name__ == "__main__":
    register()

Dependency graph: Simple exporter

This example is a combination of all previous ones, and shows how to write a simple exporter script.

import bpy


class OBJECT_OT_simple_exporter(bpy.types.Operator):
    """Simple (fake) exporter of selected objects"""
    bl_label = "DEG Export Selected"
    bl_idname = "object.simple_exporter"

    apply_modifiers: bpy.props.BoolProperty(name="Apply Modifiers")

    def execute(self, context):
        depsgraph = context.evaluated_depsgraph_get()
        for object_instance in depsgraph.object_instances:
            if not self.is_object_instance_from_selected(object_instance):
                # We only export selected objects
                continue
            # NOTE: This will create a mesh for every instance, which is not ideal at all. In
            # reality destination format will support some sort of instancing mechanism, so the
            # code here will simply say "instance this object at object_instance.matrix_world".
            mesh = self.create_mesh_for_object_instance(object_instance)
            if mesh is None:
                # Happens for non-geometry objects.
                continue
            print(f"Exporting mesh with {len(mesh.vertices)} vertices "
                  f"at {object_instance.matrix_world}")
            object_instace.to_mesh_clear()

        return {'FINISHED'}

    def is_object_instance_from_selected(self, object_instance):
        # For instanced objects we check selection of their instancer (more accurately: check
        # selection status of the original object corresponding to the instancer).
        if object_instance.parent:
            return object_instance.parent.original.select_get()
        # For non-instanced objects we check selection state of the original object.
        return object_instance.object.original.select_get()

    def create_mesh_for_object_instance(self, object_instance):
        if self.apply_modifiers:
            return object_instance.object.to_mesh()
        else:
            return object_instance.object.original.to_mesh()


def register():
    bpy.utils.register_class(OBJECT_OT_simple_exporter)


def unregister():
    bpy.utils.unregister_class(OBJECT_OT_simple_exporter)


if __name__ == "__main__":
    register()

base class — bpy_struct

class bpy.types.Depsgraph(bpy_struct)

ids

All evaluated data-blocks

Type

bpy_prop_collection of ID, (readonly)

mode

Evaluation mode

• VIEWPORT Viewport, Viewport non-rendered mode.

• RENDER Render, Render.

Type

enum in [‘VIEWPORT’, ‘RENDER’], default ‘VIEWPORT’, (readonly)

object_instances

All object instances to display or render (WARNING: only use this as an iterator, never as a sequence, and do not keep any references to its items)

Type

bpy_prop_collection of DepsgraphObjectInstance, (readonly)

objects

Evaluated objects in the dependency graph

Type

bpy_prop_collection of Object, (readonly)

scene

Original scene dependency graph is built for

Type

Scene, (readonly)

scene_eval

Original scene dependency graph is built for

Type

Scene, (readonly)

updates

Updates to data-blocks

Type

bpy_prop_collection of DepsgraphUpdate, (readonly)

view_layer

Original view layer dependency graph is built for

Type

ViewLayer, (readonly)

view_layer_eval

Original view layer dependency graph is built for

Type

ViewLayer, (readonly)

debug_relations_graphviz(filename)

debug_relations_graphviz

Parameters

filename (string, (never None)) – File Name, Output path for the graphviz debug file

debug_stats_gnuplot(filename, output_filename)

debug_stats_gnuplot

Parameters

• filename (string, (never None)) – File Name, Output path for the gnuplot debug file

• output_filename (string, (never None)) – Output File Name, File name where gnuplot script will save the result

debug_tag_update()

debug_tag_update

debug_stats()

Report the number of elements in the Dependency Graph

Returns

result

Return type

string, (never None)

update()

Re-evaluate any modified data-blocks, for example for animation or modifiers. This invalidates all references to evaluated data-blocks from this dependency graph.

id_eval_get(id)

id_eval_get

Parameters

id (ID) – Original ID to get evaluated complementary part for

Returns

Evaluated ID for the given original one

Return type

ID

id_type_updated(id_type)

id_type_updated

Parameters

id_type (enum in ['ACTION', 'ARMATURE', 'BRUSH', 'CAMERA', 'CACHEFILE', 'CURVE', 'FONT', 'GREASEPENCIL', 'COLLECTION', 'IMAGE', 'KEY', 'LIGHT', 'LIBRARY', 'LINESTYLE', 'LATTICE', 'MASK', 'MATERIAL', 'META', 'MESH', 'MOVIECLIP', 'NODETREE', 'OBJECT', 'PAINTCURVE', 'PALETTE', 'PARTICLE', 'LIGHT_PROBE', 'SCENE', 'SIMULATION', 'SOUND', 'SPEAKER', 'TEXT', 'TEXTURE', 'HAIR', 'POINTCLOUD', 'VOLUME', 'WINDOWMANAGER', 'WORLD', 'WORKSPACE']) – ID Type

Returns

Updated, True if any datablock with this type was added, updated or removed

Return type

boolean

classmethod bl_rna_get_subclass(id, default=None)

Parameters

id (string) – The RNA type identifier.

Returns

The RNA type or default when not found.

Return type

bpy.types.Struct subclass

classmethod bl_rna_get_subclass_py(id, default=None)

Parameters

id (string) – The RNA type identifier.

Returns

The class or default when not found.

Return type

type

Inherited Properties

bpy_struct.id_data

Inherited Functions

bpy_struct.as_pointer bpy_struct.driver_add bpy_struct.driver_remove bpy_struct.get bpy_struct.is_property_hidden bpy_struct.is_property_overridable_library bpy_struct.is_property_readonly bpy_struct.is_property_set bpy_struct.items bpy_struct.keyframe_delete

bpy_struct.keyframe_insert bpy_struct.keys bpy_struct.path_from_id bpy_struct.path_resolve bpy_struct.pop bpy_struct.property_overridable_library_set bpy_struct.property_unset bpy_struct.type_recast bpy_struct.values

References

BlendDataMeshes.new_from_object Context.evaluated_depsgraph_get ID.evaluated_get Object.calc_matrix_camera Object.camera_fit_coords Object.closest_point_on_mesh Object.ray_cast Object.to_mesh RenderEngine.bake

RenderEngine.render RenderEngine.update RenderEngine.view_draw RenderEngine.view_update Scene.ray_cast ShaderNodeTexPointDensity.cache_point_density ShaderNodeTexPointDensity.calc_point_density ShaderNodeTexPointDensity.calc_point_density_minmax ViewLayer.depsgraph