topic Re: Light bulb v.s. Visible in Fusion API and Scripts Forum

Light bulb v.s. Visible

j.han97 — Wed, 17 Nov 2021 03:46:43 GMT

Hi all,

What is the difference between isLightBulbOn and isVisible? I have tried both of them on a body under root component and it seems like they do exactly the same thing.

Can somebody explain the difference(s)?

Thank you so much in advance.

Re: Light bulb v.s. Visible

BrianEkins — Wed, 17 Nov 2021 06:00:32 GMT

It's possible that isLightBulbOn can return True and isVisible will return False. The isLightBulbOn gets and sets whether the eye (which used to be a light bulb) is turned on or not. The isVisible indicates the current visibility state of the body. The browser below illustrates a case where isLightBulbOn is True but isVisible is False because the body is set to display but the light bulb for its parent component is off, which turns off the visibility of everything in the component.

Re: Light bulb v.s. Visible

j.han97 — Wed, 17 Nov 2021 06:30:20 GMT

Hi @BrianEkins,

For my understanding, isVisible represents the actual state of the visibility of the object (body/occurrence), while isLightBulbOn might not. In a more direct way, if isVisible is True, the object must be visible. If isLightBulbOn is True, the object might not be visible.

Is this statement correct?

I have several questions in mind but I guess I can just experiment with it myself. Just one question I would like to ask: Is there any case/exception where setting these properties will fail? For example, when parent component has isVisible as False and I try to let one of its bodies to have isVisible = True.

Thank you very much.

Re: Light bulb v.s. Visible

BrianEkins — Wed, 17 Nov 2021 06:56:22 GMT

I would have to experiment to see what the behavior is when setting the isVisible property. I know that originally, the BrepBody object only had the isVisible property and later the isLightBulbOn was added when it was recognized there is different behavior and it wasn't possible to get the current visibility state. Because the isVisible property existed as a read-write property, changing it to read-only would break existing programs. I just did a test and setting the isVisible property is the equivalent of setting the isLightBulbOn but getting it always returns the current state. This means there are cases where you can set it to True but when you get it it will return False. It's best to consider IsVisible as read-only and use IsLightBulbOn to change the visibilty.

Re: Light bulb v.s. Visible

j.han97 — Wed, 17 Nov 2021 07:35:44 GMT

I see. Based on what I found in my testing and the information from Brian:

1. In many situations, isVisible property cannot be set (return error). Hence, it is best to be used as a read only property.

2. I can set a child occurrence's isLightBulbOn property to TRUE when its parent occurrence's isLightBulbOn property is FALSE. However, this will not change anything, i.e., the child occurrence is still not visible, and the value of child occurrence's isLightBulbOn property remains to be FALSE.

This means that in order to show a hidden object, one has to check the isLightBulbOn property of its paths (parent, parent of parent, etc) as well.

Thank you @BrianEkins for your help.