# Set edge as axis for surface rotation

Before making a dodecahedron animation I want to construct the lower half as a static object. In my screenshot you see the initial, flat construction, for which I've rotated five pentagons around the vertices of the central pentagon in order to have their edges aligned to each other. The next step would be to set those edges as each pentagon's individual axises and "fold" the pentagons, compared to folding a paper, upwards, so the neighbor edges would align, too, at a certain angle.

1. How do I set edges as axis for object rotation?
2. How do I define the meeting points of two edges?

The pivot point of selected pentagon on inner edge, the modifier's local axis is not aligned with the edge.

To rotate the faces around a specific edge, change to Edge Selection Mode, select all the edges of the face you want to rotate and select the edge that the face will be rotating around as last.

Set Pivot Point as Active Element and change Transform Orientation to Normal.

To rotate the face around that edge hit R button, then Y button twice, then type rotational angle and hit Enter.

For dodecahedron faces to meet the rotational angle should be around 63.5 degrees (arccos(1/√5)) from the grid floor.

To use the function for precise rotation, after hitting R button type:

*180*acos(1/sqrt(5))/pi


To change the angle to negative or positive use Ctrl+- buttons

• Thank you very much, Dennis, this is perfect. Do I understand correctly, that there is no way to have the exact value of 1/√5, but only the approximation of 63.5 degrees here? How do I have a chance to put all the verticies of the full dodecahedrom together later, so I have exact alignments of edges, like with a "snap" option, keeping all sides perfectly equal with no approximation used? Thank you. I don't know about how to merge edges or verticies, yet, maybe there is a tutorial on that you might recommend. – Yogi Placebo Apr 24 '15 at 16:42
• To do that make the animation of dodecahedron in reverse. – Denis Apr 24 '15 at 16:44
• @YogiPlacebo the precise angle is 63.435 degrees – Denis Apr 24 '15 at 17:09
• @YogiPlacebo To create a dodecahedron add an icosphere with one subdivision, then apply subdivision modifier with one subdivision and dissolve all the edges that connect in one point on the 5 sided face. – Denis Apr 24 '15 at 18:35