课程

How to Generate Random Numbers

教你怎么用随机数：

Python Console 下：

import random 导入随机数模块
random.uniform(0, 1) 生成一个 0-1 的随机浮点数，服从均匀分布
random.choice(range(0， 10)) 生成一个 0-10（不包含 10）的随机整数，服从均匀分布

Blender 下 print() 的输出可以在 Window-Toggle System Console 里显示。

将随机数用在插件中的示例：

import bpy
import random
from bpy.types import Panel, Operator, PropertyGroup
from bpy.props import FloatProperty, PointerProperty, IntProperty
 
 
class MyProperties(PropertyGroup):
    random_number : IntProperty(name='Random Number', default=0)
    text_list = ['A', 'B', 'C']
    icon_list = ['GHOST_DISABLED', 'MATERIAL', 'PINNED']
    
 
class ADDONNAME_PT_main_panel(Panel):
    bl_label = "Main Panel"
    bl_idname = "ADDONNAME_PT_main_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "New Tab"
 
    def draw(self, context):
        layout = self.layout
        scene = context.scene
        mytool = scene.my_tool
        
        layout.label(text=mytool.text_list[mytool.random_number])
        layout.label(icon=mytool.icon_list[mytool.random_number])
        layout.prop(mytool, "random_number")
        layout.operator("addonname.myop_operator")
 
 
class ADDONNAME_OT_my_op(Operator):
    bl_label = "Generate Random Number"
    bl_idname = "addonname.myop_operator"
        
    def execute(self, context):
        scene = context.scene
        mytool = scene.my_tool
        
        x = random.choice(range(0, 3))
        mytool.random_number = x
        print(x)
            
        return {'FINISHED'}
 
 
classes = [MyProperties, ADDONNAME_PT_main_panel, ADDONNAME_OT_my_op]

 
def register():
    for cls in classes:
        bpy.utils.register_class(cls)    
    bpy.types.Scene.my_tool = PointerProperty(type=MyProperties)
 
 
def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
        del bpy.types.Scene.my_tool
 
 
if __name__ == "__main__":
    register()

开跑，按下 Generate Random Number，就会生成一个随机数，并导致面板标题和图标的变化。

Add-on Creation - Insta-Mist

比起原先的代码，加了一些节点存在性检查：

comp_node = tree.nodes.get('Composite')
if comp_node is None:
    comp_node = tree.nodes.new('CompositorNodeComposite')
    comp_node.name = 'Composite'

render_layer_node = tree.nodes.get('Render Layers')
if render_layer_node is None:
    render_layer_node = tree.nodes.new('CompositorNodeRLayers')
    render_layer_node.name = 'Render Layers'

mix1 = tree.nodes.get('Mix')
if mix1 is not None:
    tree.nodes.remove(mix1)

mix2 = tree.nodes.get('Mix.001')
if mix2 is not None:
    tree.nodes.remove(mix2)

cr = tree.nodes.get('ColorRamp')
if cr is not None:
    tree.nodes.remove(cr)

这段代码是一个基于 Blender 的插件，用于在 3D 视图中添加雾效果。主要包含三个类 INSTAMIST_PT_main_panel、INSTAMIST_PT_sub_panel 和 INSTAMIST_OT_add_mist。

其中 INSTAMIST_PT_main_panel 是主面板类，包含一个按钮“Add Mist”，点击按钮会触发 INSTAMIST_OT_add_mist 类的 execute 方法来开启或关闭雾效果。

INSTAMIST_PT_sub_panel 是子面板类，当且仅当场景的视图层使用了 pass_mist 属性才会显示面板，其中包括了 start、depth 和 falloff 这三个属性来控制雾的起始位置、深度和衰减程度。

最后 INSTAMIST_OT_add_mist 是操作员类，通过 execute 方法来根据当前状态开启或关闭雾效果，并对节点树进行相应的操作。如果开启雾效果，则会调用 mist_comp_action 方法来添加新的节点，否则会移除原有的节点。

bl_info = {
    "name": "INSTAMIST",
    "author": "Darkfall",
    "version": (1, 0),
    "blender": (2, 90, 1),
    "location": "View3D > N > INSTA-MIST",
    "description": "Adds Mist to your scene along with arranging the compositor",
    "warning": "",
    "doc_url": "",
    "category": "Add Mist",
}
 
 
import bpy
from bpy.types import Panel, Operator
 
 
def mist_comp_action(context):
    tree = context.scene.node_tree
    
    comp_node = tree.nodes.get('Composite')
    if comp_node is None:
        comp_node = tree.nodes.new('CompositorNodeComposite')
        comp_node.name = 'Composite'
    comp_node.location = (700, 0)
    
    viewer_node = tree.nodes.new('CompositorNodeViewer')
    viewer_node.location = (700, 200)
    
    render_layer_node = tree.nodes.get('Render Layers')
    if render_layer_node is None:
        render_layer_node = tree.nodes.new('CompositorNodeRLayers')
        render_layer_node.name = 'Render Layers'
    render_layer_node.location = (-200, 0)
    
    mix_node = tree.nodes.new('CompositorNodeMixRGB')
    mix_node.location = (500, 0)
    mix_node.blend_type = 'ADD'
    mix_node.use_clamp = True
    
    mix2_node = tree.nodes.new('CompositorNodeMixRGB')
    mix2_node.location = (300, 0)
    mix2_node.blend_type = 'MULTIPLY'
    mix2_node.use_clamp = True
    
    cr_node = tree.nodes.new('CompositorNodeValToRGB')
    cr_node.location = (0, 0)
    cr_node.color_ramp.elements[0].color = (0.2, 0.2, 0.2, 1)
    cr_node.color_ramp.elements.new(position= 0.27)
    
    link = tree.links.new
    
    link(mix_node.outputs[0], viewer_node.inputs[0])
    link(mix_node.outputs[0], comp_node.inputs[0])
    link(mix2_node.outputs[0], mix_node.inputs[1])
    link(cr_node.outputs[0], mix2_node.inputs[1])
    link(render_layer_node.outputs[0], mix_node.inputs[2])
    link(render_layer_node.outputs[3], cr_node.inputs[0])
    return {'FINISHED'}
 
 
 
class INSTAMIST_PT_main_panel(Panel):
    bl_label = "INSTA-MIST"
    bl_idname = "INSTAMIST_PT_main_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "INSTA-MIST"
 
    def draw(self, context):
        layout = self.layout
        scene = context.scene
        
 
        layout.operator("instamist.add_mist_operator")
 
 
class INSTAMIST_PT_sub_panel(Panel):
    bl_label = "INSTA-MIST Options"
    bl_idname = "INSTAMIST_PT_sub_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "INSTA-MIST"
    bl_parent_id = 'INSTAMIST_PT_main_panel'
    
    @classmethod
    def poll(cls, context):
        return (context.scene.view_layers["ViewLayer"].use_pass_mist == True
)
 
    def draw(self, context):
        layout = self.layout
        scene = context.scene
        world = scene.world.mist_settings
        
        layout.prop(world, "start")
        layout.prop(world, "depth")
        layout.prop(world, "falloff")
 
 
class INSTAMIST_OT_add_mist(Operator):
    bl_label = "Enable/Disable Mist"
    bl_idname = "instamist.add_mist_operator"
    
    
    
    def execute(self, context):
        scene = context.scene
        camera = bpy.data.cameras['Camera']
        vl = scene.view_layers["ViewLayer"]
        tree = scene.node_tree
        
        if vl.use_pass_mist == False:
            vl.use_pass_mist = True
            camera.show_mist = True
            if scene.use_nodes == False:
                scene.use_nodes = True
            mist_comp_action(context)    
            
        elif vl.use_pass_mist == True:
            vl.use_pass_mist = False
            camera.show_mist = False
            
            mix1 = tree.nodes.get('Mix')
            if mix1 is not None:
                tree.nodes.remove(mix1)

            mix2 = tree.nodes.get('Mix.001')
            if mix2 is not None:
                tree.nodes.remove(mix2)

            cr = tree.nodes.get('ColorRamp')
            if cr is not None:
                tree.nodes.remove(cr)
            
            comp_node = tree.nodes.get('Composite')
            viewer_node = tree.nodes.get('Viewer')
            render_layer_node = tree.nodes.get('Render Layers')
            
            tree.links.new(render_layer_node.outputs[0], comp_node.inputs[0])
            tree.links.new(render_layer_node.outputs[0], viewer_node.inputs[0])
        return {'FINISHED'}
    
 
classes = [INSTAMIST_PT_main_panel, INSTAMIST_OT_add_mist, INSTAMIST_PT_sub_panel]
 
 
 
def register():
    for cls in classes:
        bpy.utils.register_class(cls)
        
 
def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
 
 
if __name__ == "__main__":
    register()

开跑！按下 Enable/Disable Mist 后，会在 Compositor 生成/删除节点，以开启/关闭雾效果。

按下 F12 就可以看到渲染后的效果：

Lists - Create, Append and Remove

Darkfall : Blender Python Tutorial: Lists - Create, Append and Remove (darkfallblender.blogspot.com)

教你怎么用 python 里的 list：

list.append() 追加一个元素
list.remove() 删除一个元素
list.extend() 追加多个元素
list.clear() 清空列表

import bpy
from bpy.types import Panel, Operator, PropertyGroup
from bpy.props import EnumProperty, PointerProperty, StringProperty
 
 
class MyProperties(PropertyGroup):
    
    my_enum : EnumProperty(
        name= "Enumerator / Dropdown",
        description= "sample text",
        items= [('OP1', "Append", ""),
                ('OP2', "Remove", "")
        ]
    )
    
    new_item : StringProperty()
    my_list = []
 
class ADDONNAME_PT_main_panel(Panel):
    bl_label = "Main Panel"
    bl_idname = "ADDONNAME_PT_main_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "New Tab"
 
    def draw(self, context):
        layout = self.layout
        scene = context.scene
        mytool = scene.my_tool
        
        
        layout.prop(mytool, "my_enum", expand=True)
        layout.prop(mytool, 'new_item')
        layout.operator("addonname.myop_operator")
 
 
 
 
 
class ADDONNAME_OT_my_op(Operator):
    bl_label = "Submit"
    bl_idname = "addonname.myop_operator"
    
    def execute(self, context):
        scene = context.scene
        mytool = scene.my_tool
        list = mytool.my_list
        enum = mytool.my_enum
        new_item = mytool.new_item
        
        a = 'alpha'
        b = 'beta'
        
        if enum == 'OP1':
            if a and b not in list:
                list.extend((a, b))
            if new_item != '':
                if new_item not in list:
                    list.append(new_item)
        else:
            list.clear()
        print(list)
        
        return {'FINISHED'}
    
 
 
 
classes = [MyProperties, ADDONNAME_PT_main_panel, ADDONNAME_OT_my_op]
  
 
def register():
    for cls in classes:
        bpy.utils.register_class(cls)
        
    bpy.types.Scene.my_tool = PointerProperty(type= MyProperties)
 
def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
    del bpy.types.Scene.my_tool
 
 
 
if __name__ == "__main__":
    register()

How to Display Info Messages

Darkfall : Blender Python Tutorial: How to Display Info/ Error Messages to the User [learn python for beginners] (darkfallblender.blogspot.com)

介绍了一些可以将消息输出至 Info 的语句：

self.report({'INFO'}, "This is a Custom Message")
self.report({'WARNING'}, "This is a Custom Message")
self.report({'ERROR'}, "This is a Custom Message")

Why is it not Working? : Episode 1

教你怎么调试错误。

How to make a Random Word Generator

Darkfall : Blender Python Tutorial: How to Create a Random Word Generator [Learn Python for beginners] (darkfallblender.blogspot.com)

写了一个随机单词生成器：

bl_info = {
    "name": "Random Word Generator",
    "author": "Darkfall",
    "version": (1, 0),
    "blender": (2, 90, 1),
    "location": "View3D > N > Random Word Gen Tab",
    "description": "Generates a Random Phrase",
    "warning": "",
    "doc_url": "",
    "category": "Add Words",
}
 
import bpy
from bpy.types import Panel, Operator, PropertyGroup
from bpy.props import IntProperty, PointerProperty, BoolProperty
from random import randint
 

class RandomWordGenProperties(PropertyGroup):
    
    list_a = ["A", "Dr", "Mr", "Mrs", "Our", "The"]
    
    list_b = ["Adorable", "Adventurous", "Agressive", "Agreeable", "Angry", "Annoyed", "Annoying", "Anxious", "Arrogant", "Attractive", "Average", "Awful", "Bad", "Beautiful", "Better", "Bewildered", "Bloody", "Blushing", "Bored", "Brainy", "Brave", "Breakable", "Bright", "Broken", "Bronze", "Busy", "Calm", "Careful", "Cautious", "Charming", "Cheerful", "Clean", "Clear", "Clever", "Cloudy", "Clumsy", "Colorful", "Comfortable", "Condemned", "Confused", "Cooperative", "Courageous", "Crazy", "Creepy", "Crowded", "Cruel", "Curious", "Cute", "Dangerous", "Dark", "Dead", "Defeated", "Defiant", "Delightful", "Depressed", "Determained", "Different", "Difficult", "Disgusted", "Doubtful", "Dull", "Eager", "Easy", "Elated", "Elegant", "Embarrassed", "Enchanting", "Encouraging", "Energetic", "Enthusiastic", "Envious", "Evil", "Excited", "Expensive", "Exuberant", "Faithful", "Famous", "Fancy", "Fantastic", "Fierce", "Filthy", "Fine", "Foolish", "Fragile", "Frail", "Frantic", "Friendly", "Frightened", "Frozen", "Funny", "Gentle", "Gifted", "Glamorous", "Gleaming", "Glorious", "Good", "Gold", "Golden", "Gorgeous", "Graceful", "Greiving", "Grotesque", "Grumpy", "Handsome", "Happy", "Healthy", "Helpful", "Helpless", "Hilarious", "Horrible", "Hungry", "Hurt", "Important", "Impossible", "Industrial", "Inexpensive", "Innocent", "Inquisitive", "Itchy", "Jelous", "Jolly", "Joyous", "Kind", "Lazy", "Light", "Lively", "Lonely", "Long", "Lovely", "Lucky", "Magnificent", "Misty", "Modern", "Motionless", "Muddy", "Mushy", "Mysterious", "Nasty", "Naughty", "Nervous", "Never-ending", "Nice", "Obedient", "Obnoxious", "Odd", "Old", "Old-fashoined", "Open", "Outrageous", "Outstanding", "Perfect", "Plain", "Pleasant", "Poised", "Poor", "Powerful", "Precious", "Proud", "Putrid", "Puzzled", "Quaint", "Real", "Relieved", "Repulsive", "Rich", "Righteous", "Rival", "Rusty", "Secret", "Scary", "Silver", "Silvery", "Selfish", "Shiny", "Shy", "Silly", "Sleepy", "Smiling", "Sore", "Sparkling", "Splendid", "Spotless", "Stalking", "Steady", "Strange", "Stranger", "Stupid", "Subtle", "Successful", "Super", "Talented", "Tame", "Tender", "Tense", "Terrible", "Thankful", "Thoughful", "Thoughtless", "Tired", "Tough", "Troubled", "Ugliest", "Ugly", "Unsightly", "Unusual", "Upset", "Uptight", "Vast", "Victorious", "Wandering", "Weary", "Wicked", "Wild", "Witty", "Worried", "Wrong", "Zelous"]
    
    list_c = ["Actor", "Anchor", "Antagonist", "Apple", "Angel", "Angle", "Army", "Astronaut", "Ball", "Balloon", "Beach", "Bear", "Beast", "Book", "Brain", "Cake", "Castle", "Coast", "Colony", "Complex", "Conundrum", "Core", "Crowd", "Dancer", "Detective", "Detector", "Devil", "Director", "Diver", "Driver", "Express", "Factory", "Family", "Forest", "Future", "Gamer", "Garden", "Hacker", "Hangman", "History", "House", "Idea", "Island", "Jail", "Jester", "Joker", "King", "Knight", "Lake", "Lighthouse", "Matrix", "Mind", "Monument", "Moon", "Mountain", "Navy", "Nail", "Night", "Office", "Officer", "Operator", "Page", "Park", "Path", "Pickle", "Pizza", "Place", "Planet", "Player", "Picture", "Price", "Prince", "Princess", "Prison", "Program", "Programmer", "Protagonist", "Queen", "Razor", "Rifle", "Ring", "Reptile", "Road", "River", "Science", "Situation", "Society", "Soldier", "Sound", "Steed", "Story", "Surface", "Tavern", "Tower", "Traveler", "Tree", "Undead", "Unicorn", "Vampire", "Warrior", "Wizard", "World", "Wolf", "Zombie"]
    
    number_1 : IntProperty(default= 0)
    number_2 : IntProperty(default= 0)
    number_3 : IntProperty(default= 0)

    number_4 : IntProperty(default= 1)
    
    word_count : IntProperty(default= 3, min= 1, max= 3, description= "Select How Many Words to be Generated")
    
    wc_bool : BoolProperty(default= False, description= "Selecting this Option will randomize the Word Count")
    
    
class RANDOMWORDGEN_PT_main_panel(Panel):
    bl_label = "Random Word Generator"
    bl_idname = "RANDOMWORDGEN_PT_main_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "Random Word Gen"
 
    def draw(self, context):
        layout = self.layout
        scene = context.scene
        mytool = scene.my_tool
        
        wc = mytool.word_count
        r_wc = mytool.wc_bool
  
        if r_wc == False:
            layout.prop(mytool, "word_count", text= "Word Count")
            row = layout.row()
        
            if wc >= 1:
                row.label(text= mytool.list_a[mytool.number_1])
            if wc >= 2:
                row.label(text= mytool.list_b[mytool.number_2])
            if wc >= 3:
                row.label(text= mytool.list_c[mytool.number_3])
        else: 
            row = layout.row()
            if mytool.number_4 >= 1:
                row.label(text= mytool.list_a[mytool.number_1])
            if mytool.number_4 >= 2:
                row.label(text= mytool.list_b[mytool.number_2])
            if mytool.number_4 >= 3:
                row.label(text= mytool.list_c[mytool.number_3])
        layout.prop(mytool, "wc_bool", text= "Randomize Word Count")        
                            
        layout.operator("randomwordgen.myop_operator")
 

class RANDOMWORDGEN_OT_my_op(Operator):
    bl_label = "Generate Random Words"
    bl_idname = "randomwordgen.myop_operator"
    
    
    def execute(self, context):
        scene = context.scene
        mytool = scene.my_tool
        
        a = 0
        
        b2 = len(mytool.list_a)
        b = b2 - 1
        
        c2 = len(mytool.list_b)
        c = c2 - 1
        
        d2 = len(mytool.list_c)
        d = d2 - 1
        
        e = 1
        f = 3
        
        r1 = randint(a, b)
        r2 = randint(a, c)
        r3 = randint(a, d)
        
        r4 = randint(e, f)
        
        mytool.number_1 = r1
        mytool.number_2 = r2
        mytool.number_3 = r3
        
        mytool.number_4 = r4
        
        return {'FINISHED'}

 
classes = [RandomWordGenProperties, RANDOMWORDGEN_PT_main_panel, RANDOMWORDGEN_OT_my_op]
 
 
def register():
    for cls in classes:
        bpy.utils.register_class(cls)
        
    bpy.types.Scene.my_tool = PointerProperty(type= RandomWordGenProperties)


def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
    del bpy.types.Scene.my_tool
 
 
if __name__ == "__main__":
    register()

点击 Generate Random Words 就可以从单词库中生成一堆单词！

Application Timers

这段代码是一个简单的 Blender Python 脚本，用于创建 10 个位置不同的立方体。该脚本使用了 Blender 的定时器功能，以便在指定时间间隔内反复调用函数 "run_10_times()"。

首先，使用 import bpy 导入必要的 Blender Python 模块。

然后，创建了全局变量 counter 和 loc, 分别用于追踪立方体数量和立方体位置。

接下来定义函数 run_10_times(), 它会在启动定时器后被调用。该函数使用 bpy.ops.mesh.primitive_cube_add() 命令在场景中添加一个立方体。该命令需要一个位置参数，它将使用 loc 变量中的值来确定立方体的垂直位置。然后，counter 变量增加 1，loc 变量增加 2（以确保每个立方体都有不同的位置）。

函数还打印出当前计数器值。

如果 counter 变量的值达到 10，函数返回 None，以便停止定时器。否则，它将返回 0.5，以便等待一段时间（0.5s）后再次调用该函数。

最后，通过 bpy.app.timers.register() 函数注册函数 run_10_times()，以便在 Blender 中启动定时器。该函数将在 Blender 界面中点击 "Run Script" 按钮后执行。

总之，该脚本使用 Blender Python 的定时器功能，创建 10 个位置不同的立方体，每个立方体之间延迟一定时间。

import bpy

counter = 0
loc = 0


def run_10_times():
    global loc
    bpy.ops.mesh.primitive_cube_add(location=(0, loc, 0))
    global counter
    counter += 1
    loc += 2
    print(counter)
    if counter == 10:
        return None
    return 0.5


bpy.app.timers.register(run_10_times)

Why is it not Working? : Episode 2

这段代码是一个 Blender 插件的示例，定义了一个面板和一个操作符。该插件提供了一些功能来添加粒子系统到选择的对象中。

首先，导入必要的模块，包括 bpy 和 Panel、Operator 类型。

接下来定义了一个面板类 ADDONNAME_PT_main_panel，并从 Panel 类继承。在这个类中设置了一些属性，例如名称、区域类型和分类等。draw() 方法用于绘制面板中的内容，在这里使用 layout 属性创建了三个控件，包括两个用于设置粒子系统参数的属性和一个用于执行操作的按钮。

然后定义了一个操作符 ADDONNAME_OT_my_op，并从 Operator 类继承。在这个类中设置了一些属性，例如名称和 ID 名称等。execute() 方法是操作符的核心部分，它将在用户按下按钮时被调用。在这里，它使用 bpy.ops.object.particle_system_add() 命令向选定的对象中添加了一个粒子系统。

最后，将 ADDONNAME_PT_main_panel 和 ADDONNAME_OT_my_op 类添加到 classes 列表中，并使用 bpy.utils.register_class() 函数注册这些类。同样，使用 unregister() 函数在插件不再需要时注销这些类。

如果这个脚本是直接运行的，那么它将调用 register() 方法并注册这些类。如果该脚本作为其他插件的一部分被导入，则 register() 方法不会被调用。

import bpy
from bpy.types import Panel, Operator
 

class ADDONNAME_PT_main_panel(Panel):
    bl_label = "Main Panel"
    bl_idname = "ADDONNAME_PT_main_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "New Tab"
 
 
    def draw(self, context):
        layout = self.layout
        
        p_data = bpy.data.particles["ParticleSettings"]
        
        layout.prop(p_data, "count")
        layout.prop(p_data, "use_rotations")
        if p_data.use_rotations == True:
            layout.prop(p_data, "rotation_factor_random")
        layout.operator("addonname.myop_operator")


class ADDONNAME_OT_my_op(Operator):
    bl_label = "Add Particle System"
    bl_idname = "addonname.myop_operator"
    """Add a Particle System to your Selected Object"""
    

    def execute(self, context):
        scene = context.scene
        obj = context.object
        bpy.ops.object.particle_system_add()    
        return {'FINISHED'}
    

classes = [ADDONNAME_PT_main_panel, ADDONNAME_OT_my_op]
 

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

 
if __name__ == "__main__":
    register()

The REDO Operator

这段代码是 Blender 插件的示例，定义了一个面板和一个操作符。该插件提供一个按钮，点击后会在当前场景中添加一个立方体。

首先导入必要的模块，包括 bpy 和 Panel、Operator 类型。

然后定义了一个面板类 ADDONNAME_PT_main_panel，并从 Panel 类继承。在这个类中设置了一些属性，例如名称、区域类型和分类等。draw() 方法用于绘制面板中的内容，在这里使用 layout 属性创建了一个控件，即一个按钮，并使用 layout.operator() 函数将其添加到面板中。

接着定义了一个操作符 ADDONNAME_OT_my_op，并从 Operator 类继承。在这个类中设置了一些属性，例如名称和 ID 名称等。bl_options 属性指定了操作符的行为，包括注册和撤销。loc 属性是一个 FloatVectorProperty，表示要添加的立方体的位置。

execute() 方法是操作符的核心部分，它将在用户按下按钮时被调用。在这里，它使用 bpy.ops.mesh.primitive_cube_add() 命令向当前场景中添加了一个立方体，位置由 self.loc 属性决定。

最后，将 ADDONNAME_PT_main_panel 和 ADDONNAME_OT_my_op 类添加到 classes 列表中，并使用 bpy.utils.register_class() 函数注册这些类。同样，使用 unregister() 函数在插件不再需要时注销这些类。

如果这个脚本是直接运行的，那么它将调用 register() 方法并注册这些类。如果该脚本作为其他插件的一部分被导入，则 register() 方法不会被调用。

bl_options = {'REGISTER', 'UNDO'}
- bl_options 是一个操作符的属性，用于指定该操作符的行为。它是一个包含字符串的集合，可以指定以下选项：
  - REGISTER：表示将该操作作为已注册的操作来显示，即将其添加到撤销历史记录中。如果未启用此选项，则执行该操作不会被记录在撤销历史记录中。
  - UNDO：表示该操作可被撤销。如果未启用此选项，则在执行该操作后无法撤消该操作。
  在代码示例中，bl_options 属性被设置为 {'REGISTER', 'UNDO'}，表示该操作符应被注册并可以被撤销。这样一来，当用户单击添加的按钮时，该操作的执行将被记录在撤销历史记录中，并且用户可以随时撤消该操作。
在 Blender 中，可以使用 Ctrl + Z 快捷键或 Edit 菜单中的 Undo 命令来撤消先前执行的操作。如果你想一次性撤销多个操作，可以多次按下 Ctrl + Z 或多次选择 Undo 命令。

如果你想恢复先前撤消的操作，可以使用 Ctrl + Shift + Z 快捷键或 Edit 菜单中的 Redo 命令来重做操作。同样，你可以多次按下 Ctrl + Shift + Z 或多次选择 Redo 命令以重复多个操作。

import bpy
from bpy.types import Panel, Operator


class ADDONNAME_PT_main_panel(Panel):
    bl_label = "Main Panel"
    bl_idname = "ADDONNAME_PT_main_panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_category = "New Tab"

    
    def draw(self, context):
        layout = self.layout
 
        layout.operator("addonname.myop_operator")

 
class ADDONNAME_OT_my_op(Operator):
    bl_label = "Button"
    bl_idname = "addonname.myop_operator"
    bl_options = {'REGISTER', 'UNDO'}
    
    loc : bpy.props.FloatVectorProperty()
    
    def execute(self, context):
        bpy.ops.mesh.primitive_cube_add(location=self.loc)
        return {'FINISHED'}
 
 
classes = [ADDONNAME_PT_main_panel, ADDONNAME_OT_my_op]
 
 
def register():
    for cls in classes:
        bpy.utils.register_class(cls)
        
 
def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
 

if __name__ == "__main__":
    register()

开跑！按下 Button 按钮后，将会生成一个正方体，同时出现一个 Dialogbox 用于控制正方体的位置。这个操作可以用 Ctrl+Z 来撤销。

API Changes and where to Find them?

说 Blender 更新到 3.0 了，一些 API 发生了变化，可以从 Reference/Release Notes/3.0/Python API - Blender Developer Wiki 里查看，其实现在也可以 chatGPT。