Consider this question on a programming site (the question relates to renderers, ignore that).

enter image description here

Selecting an unseen "back" part on a 3D object has wide application.

In fact,

i) When the user selects a "back" object, what is the best way to then show the whole object ... transparent, with only the selected object solid? (roughly as seen in the example there) wireframe? Something else? Many questions arise such as ... should you during that state reduce the whole object to only an overall outline (whether transparent/whatever) or indeed still show each part (again whether transparent/whatever), if highlighted how so, etc.


ii) How would you select by pointer "through" an object, consider the case there might be not only one but a few parts "in the line of" your pointer position through the 3D object.

Indeed, have any standards emerged for this unknown to me? Do any whacky ideas come to mind: perhaps a "mirror" behind, or some sort of spatially cueing object comes in to play.

This could have particular application when using 3D mouse or virtual gloves - it would become a very common problem, how to show a 3D object when you reach "through" to a part which is not visible from the current normally-rendered view.

1 Answer 1


Great question. I have a clear image of the solution in mind and I cannot trace it to the source, maybe it was a certain mode in 3ds Max.

So when the user hovers over objects, both on the front pane and the back pane (since front and back objects are overlapping on a 2D screen), and only the front pane objects are visible, all objects get a stroke highlight, for instance, lime green, but objects of the front are filled, and objects of the back pane are only stroked. So user kind of "sees through" the front pane.

Another solution would be to render all objects as stroked only and dim the deeper ones to display the depth, but highlight them on hover. As soon as user picks up the right object by hovering it, she can select it by click. This device is a great illustration why showing depth might be a good idea: nurses see the veins but they don't know where they are on a Z axis. http://m.thetechjournal.com/tech-news/vein-detecting-device.xhtml

P.s. transparency might be tricky because if everything is semi-transparent, and there are several objects on top of each other, it can be tricky to tell which is which.

  • 1
    Hi Zoe, great ideas, your 2nd paragraph is particularly insightful. Cheers Joey
    – Fattie
    Commented Dec 29, 2015 at 23:17

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