API • Page 23 of 29 • B3D

How to switch between flat and smooth shading through the Blender Python API

Leave a Comment / Blender 3D / Nikita / 03.07.2020

The flat/smooth shading mode is regulated through the “use_smooth” property of each polygon of the mesh.

To enable smooth shading we need to set the “use_smooth” property of each mesh polygon to “True”.

For active object:

bpy.context.object.data.polygons.foreach_set('use_smooth',  [True] * len(bpy.context.object.data.polygons))

1	bpy.context.object.data.polygons.foreach_set('use_smooth', [True] * len(bpy.context.object.data.polygons))

To enable flat shading – set the “use_smooth” property of each polygon to “False”.

bpy.context.object.data.polygons.foreach_set('use_smooth',  [False] * len(bpy.context.object.data.polygons))

1	bpy.context.object.data.polygons.foreach_set('use_smooth', [False] * len(bpy.context.object.data.polygons))

To make new shading mode visible – force update mesh data:

bpy.context.object.data.update()

1	bpy.context.object.data.update()

Switching to the view from camera throug the python API

1 Comment / Blender 3D / Nikita / 19.06.2020

To switch to the view from the active camera we can execute the following command:

bpy.ops.view3d.view_camera()

1	bpy.ops.view3d.view_camera()

This operator works in the toggle mode, so the next executing of the same command returns the view to the previous state.

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Switching between coordinate systems

2 Comments / Blender 3D / Nikita / 17.06.2020

To switch from a global coordinate system to a local coordinate system of an object, we need to multiply the global coordinates by the inverted matrix of an object:

import copy

object_matrix_inverted = copy.copy(bpy.context.object.matrix_world)
object_matrix_inverted.invert()
cursor_location_local = object_matrix_inverted @ bpy.context.scene.cursor.location

import copy

object_matrix_inverted = copy.copy(bpy.context.object.matrix_world)

object_matrix_inverted.invert()

cursor_location_local = object_matrix_inverted @ bpy.context.scene.cursor.location

To switch from the local coordinate system of the object to the global coordinate system, we need to multiply the local coordinates by the matrix of an object:

import copy

object_matrix = copy.copy(bpy.context.object.matrix_world)
vertex_0 = bpy.context.object.data.vertices[0].co
vertex_0_global = object_matrix @ vertex_0

import copy

object_matrix = copy.copy(bpy.context.object.matrix_world)

vertex_0 = bpy.context.object.data.vertices[0].co

vertex_0_global = object_matrix @ vertex_0

Edit Source

Leave a Comment / Blender 3D / Nikita / 08.06.2020

For those who want to know “how Blender works” to write their own scripts and add-ons, the developers have provided a very convenient option – the ability to view any element source code in a single click.

To see the source code of any element: open the “Text Editor” window; then simply click on the desired element with the right mouse button and select “Edit Source”.

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Objects pointers brokes if undo/redo operation is used

Leave a Comment / Blender 3D / Nikita / 25.05.2020

In Blender 2.8x the undo/redo operation system (ctrl+z / ctrl+shift+z) has been completely rebuilt. One of the results of this API change is when the undo operation is performed, all objects in the scene are fully recreated – the current object is destroyed, and a completely new object is created instead. Pointers to the old objects (before the undo operation) now point to invalid objects that can no longer be used.

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User interface elements alignment by columns

Leave a Comment / Blender 3D / Nikita / 13.05.2020

Interface elements in custom user panels often do not correspond to each other in size. As a result – the overall panel layout does not look beautiful. As an example, let’s create a custom panel and place an operator button and an input text field on it.

Can we make it more accurate?

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How to get all collectons list

2 Comments / Blender 3D / Nikita / 24.04.2020

To get a list of collections with all internal collections, we can use the following function:

def collections(collection, col_list):
    col_list.append(collection)
    for sub_collection in collection.children:
        collections(sub_collection, col_list)

def collections(collection, col_list):

col_list.append(collection)

for sub_collection in collection.children:

collections(sub_collection, col_list)

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Setting operator parameters features

Leave a Comment / Blender 3D / Nikita / 18.03.2020

When you make a button in a custom UI to call the operator with passing the necessary parameters to it, pay attention that only the parameters specified explicitly will be sent to the operator. Other operator parameters will remain with default values.

For example, we need to execute the “transform_apply” operator – applying object transformations with applying just the scale.

If we call the operator as follows:

class TESTPANEL_PT_panel(Panel):
    bl_idname = 'TESTPANEL_PT_panel'
    bl_label = 'Testpanel'
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = 'Testpanel'

    def draw(self, context):
        self.layout.operator('context.object.transform_apply', text='Apply Scale').scale = True