Custom property for Dimensions field

April 13, 2026

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by Tcll

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So what I'm ultimately trying to do is calculate the length of a curve using a round-about method with an Array modifier on another object... ↩ Reply

But what I'd like to be able to do is edit the curve while seeing that length update as I edit... ↩ Reply

The only way I can fathom to do as such is with a driver on a Custom property for this field: ↩ Reply

But I'm not sure where exactly I'd need to do that, or with what... ↩ Reply

Maybe a script could do it, but I'm not sure how :P ↩ Reply

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Blender Dumbass c:0 April 13, 2026

For the context it seems like this is Blender 2.79 and not a modern Blender. Which complicates things since Blender did a lot of changes to the depsgraph since that.

Blender Dumbass c:1 April 13, 2026

I think the most low-tech solution would be to split the frame and focus one side on the length object. While having like a model of a ruler next to it.

... replies ( 1 )

Tcll c:2 April 13, 2026

@blenderdumbass

lol that reminds me of what I used to do to make outline curves for SVG art (I no longer use this as PyCharm is a better SVG editor capable of proper outlines that don't look polygonal) XD

you needed a separate frame just to modify the stroke-width curve, and it got rather insane quite rapidly XD

both that and this are ghetto af XD

for a makeshift ruler, I'd say you actually don't need much to make that work...

the Array object can just have a fixed unit-width that can easily be tracked, say 0.01 for precision

then all you really need is to offset a marker object to the desired length the Array object will extend to

you don't even need to have the entire length in view, just a good portion before the marker should be good enough :P

though it would still be nice to see the actual number rather than having to flip between object selections to verify accuracy... heh :P

Tcll c:2 April 13, 2026

... c:1

Blender Dumbass c:1 April 13, 2026

I think the most low-tech solution would be to split the frame and focus one side on the length object. While having like a model of a ruler next to it.

@blenderdumbass

lol that reminds me of what I used to do to make outline curves for SVG art (I no longer use this as PyCharm is a better SVG editor capable of proper outlines that don't look polygonal) XD

you needed a separate frame just to modify the stroke-width curve, and it got rather insane quite rapidly XD

both that and this are ghetto af XD

for a makeshift ruler, I'd say you actually don't need much to make that work...

the Array object can just have a fixed unit-width that can easily be tracked, say 0.01 for precision

then all you really need is to offset a marker object to the desired length the Array object will extend to

you don't even need to have the entire length in view, just a good portion before the marker should be good enough :P

though it would still be nice to see the actual number rather than having to flip between object selections to verify accuracy... heh :P

Blender Dumbass c:3 April 13, 2026

Figured something out... you can technically stuff a python expression referencing a specific value in the scene.

bpy.data.objects["Cube.001"].dimensions.z

this is what I put into the driver of cube 1 to make it move to the size of cube 2. And not just scale, but the dimension. But since depsgraph is not particularly great in blender 2.79. It doesn't update automatically.

... replies ( 1 )

Blender Dumbass c:4 April 13, 2026

Okay. Blender has templates in the Text Editor that spawn example code for how to add functionality. I modified one a bit and got this:

import bpy


class HelloWorldPanel(bpy.types.Panel):
    """Creates a Panel in the Object properties window"""
    bl_label = "Size Panel"
    bl_idname = "OBJECT_PT_hello"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "object"

    def draw(self, context):
        layout = self.layout
        row = layout.row()
        row.label(text="SIZE IS: " + str(bpy.data.objects["Cube.001"].dimensions.z))


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


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


if __name__ == "__main__":
    register()

It spawns a little size thingie in the Object properties. And it is updated in real time. Using the example dimensions from

Blender Dumbass c:4 April 13, 2026

Okay. Blender has templates in the Text Editor that spawn example code for how to add functionality. I modified one a bit and got this:

import bpy


class HelloWorldPanel(bpy.types.Panel):
    """Creates a Panel in the Object properties window"""
    bl_label = "Size Panel"
    bl_idname = "OBJECT_PT_hello"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "object"

    def draw(self, context):
        layout = self.layout
        row = layout.row()
        row.label(text="SIZE IS: " + str(bpy.data.objects["Cube.001"].dimensions.z))


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


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


if __name__ == "__main__":
    register()

It spawns a little size thingie in the Object properties. And it is updated in real time. Using the example dimensions from

... c:3

Blender Dumbass c:3 April 13, 2026

Figured something out... you can technically stuff a python expression referencing a specific value in the scene.

bpy.data.objects["Cube.001"].dimensions.z

this is what I put into the driver of cube 1 to make it move to the size of cube 2. And not just scale, but the dimension. But since depsgraph is not particularly great in blender 2.79. It doesn't update automatically.

Tcll c:5 April 14, 2026

awesome, that worked perfectly!

I even multiplied the dimension value by 10 and marked it with mm (my grid is unit-accurate to cm, so it works out nicely)

but yeah here it is to show: :)

Custom property for Dimensions field

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