[RFC] Visual feedback for rotate/move tools

[Staffan <gi...@kt...>]

Hi,

I've been giving the implementation of visual feedback for the rotate and move 
tools a lot of thought lately. The topic has been up here for discussion 
before, but I thinks it's worth revisiting before I invest a lot of time 
implementing something that may not be right in the end.

1) I'm having a hard time coming up with a good name for the functionality - 
what should it be called? Tool feedback mode? Feedback mode? Tool markers? 
Tool mode?

2) What axis/pivot options will be available for the rotate tool?

I believe Anders and I both agree that using average parent/local axes is 
pointless. Which leaves us with these candidates: 

Axes:
 * individual local
 * individual parent
 * world
 * (and maybe a user-specified axis and in the future?)

Pivot:
 * individual local origin
 * individual parent origin
 * world origin (and in the future, maybe another fixed, common point)
 * average origin of selected objects

The questions is which combinations that will be available. If all 
combinations are allowed, the best possible option, that I could think of, 
for visualizing the rotate tool is to draw the tripods in the object origins, 
markers in the pivots and dashed lines between them. Disabled axes will be 
grayed, semi-transparent or in some other fashion "disabled".

If the cases where each object is rotated about different axes but around the 
same pivot are disallowed, then drawing the tripods in the pivots is also an 
option. (Drawing the tripods in the pivot when all objects share the same 
pivot but have different axes will look messy and ugly since all tripods will 
be drawn in the same location.)

Unless someone can come up with a compelling reason the latter is better my 
gut feeling tells me the former is the better option since it should be a 
slight bit easier to implement (no special cases).

What do you think?

/Staffan