- [Tutor] Object transforms, move, rotate, and scale,
are calculated relative to the object's pivot point,
sometimes known as an anchor point.
That's the center of the object transforms.
And by default, for example, if we rotate an object,
it'll rotate around its pivot point.
And that's useful especially for animation.
In animation we actually need,
to always rotate around the pivot point.
But in modeling and layout,
sometimes people want to do things,
like move or rotate a whole selection of objects,
around their common center,
or maybe move or rotate objects around the origin,
or around some other object.
And we can do that,
using this button here on the main toolbar.
It's called the Use Transform Coordinate Center Flyout.
That's a bit of a mouthful,
but if you click and hold your mouse button down on that,
you'll see it as a flyout.
It's got three options.
The top one is Use Pivot Point Center,
the middle one is Use Selection Center,
the bottom one is Use Reference Coordinate Center.
Your choice here will determine,
what the center of your current transforms will be.
Now the default is Pivot Point.
So if I select something such as one of these magazines,
and go to the rotate tool,
and rotate, for example, in the View Coordinate System,
that magazine's going to rotate,
around its own pivot point, okay.
So that's pretty obvious and nothing special going on there.
But if I want to rotate, let's say this whole table,
and maintain the relationship,
between the table and those magazines,
then I would want to rotate around their common center.
Because there's no hierarchy here.
The magazines are not parented or linked to the table.
So watch what happens here.
We're currently in Use Pivot Point Center mode.
I'll drag a selection rectangle around all those objects.
And all of a sudden now, this has changed.
Now it says Use Selection Center.
And happened automatically.
And now the manipulator, the Rotate gizmo,
is positioned at the average location,
of all of the object pivot points.
It's not exactly in the center of the table,
because it's also taking the positions,
of these magazine's pivot points into account,
so I can rotate.
And I'm rotating all those objects,
around the average position of all of their pivot points.
Okay. I'll undo that with Control + Z.
So this is going to change automatically,
depending upon what we have selected.
If I deselect all those objects,
I go back to Use Pivot Point Center.
Now just to complicate things,
if it's a group,
a group is a collection of objects.
So for example, if I click on the table itself,
and not the magazines,
now we're dropped into Use Selection Center,
because that table is actually tabletop,
and some legs and some other hardware.
It's a whole collection of objects.
It's a multi-object selection,
and that has just automatically dropped us,
into Use Selection Center, okay.
So that's going to happen automatically,
unless you explicitly choose some mode.
If we actually go up here and change this to something,
then that will stick,
and it won't continue to switch back and forth.
So for example,
I could explicitly choose Use Selection Center,
and then I could select some individual object,
the icon didn't change.
I'm still in Use Selection Center.
But in this case it's effectively the same,
'cause I've only selected one object.
And the selection center of that object,
is the average of all of its pivot points,
which is just the pivot point of the object, all right.
So that's how we can, for example,
select a whole bunch of objects,
and rotate them all around their common center,
using Selection Center Mode.
I'll undo that with Control + Z.
Now this is really only going to be effective or useful,
in View or World coordinates.
If you try to use some other coordinate system like Gimbal,
this whole system's not going to work at all.
It really relies upon World coordinates.
It needs to know,
where all those pivot points are,
in order to find their average,
and that only works if you're in World coordinates,
or View coordinates in this case.
And finally you can choose Use Reference Coordinate System.
If you choose that,
then the Gizmo will be placed,
at the location that is determined,
by the Reference Coordinate System,
you've currently chosen, okay.
So if we choose Use Reference Coordinate System,
and we're in the View Coordinate System,
the Rotate Gizmo is going to be placed,
at the center of the current viewport.
And I can pan around with the middle mouse button.
You'll see, we are maintaining the position,
of that manipulator or Gizmo,
in the center of the current viewport.
So that's going to be the reference point for rotations.
If I pan over here, then I'll rotate around that location.
Okay. I'll undo that with Control + Z.
If we go out to our four viewport layout, with Alt + W,
we can see that the manipulator, the Gizmo,
is positioned at that location.
And again, if I pan around,
in that top viewport, we can see,
that our reference point is changing for rotations.
It's going to maintain the center of that top viewport,
but that's going to change in the World,
depending upon how I've panned in that view, okay.
Well, the most useful thing to do,
with this Use Reference Coordinate System mode,
is to rotate around the origin or around some object, okay.
So I could just switch this over into World coordinates,
and now we'll see,
that the Rotate Gizmo is positioned at the origin,
at the intersection of the X, Y and Z axis,
of the World grid.
And when I rotate, I'm going to rotate around the origin.
Okay. Undo that with Control + Z.
And finally, we can rotate,
around some arbitrary object by picking it.
So for example, maybe I want,
to rotate around this magazine.
So I can go up to my Reference Coordinate System pull down,
and choose Pick.
And then I need to click on some object.
I need to select something,
either in the viewport, or in some dialogue box.
You can see that my icon turns into a heavy cross,
as soon as I hover over some object.
Now this is a little bit tricky with groups.
This Pick tool will actually pick,
whatever individual object is in the group,
that's under your cursor.
So that's kind of tricky.
So let's start by just selecting something,
that's not a group, one of these magazines.
So I'll click on magazine.
And now up here,
the Reference Coordinate System has the name of that object.
And it's truncated.
There's not enough space horizontally here,
to display the name,
but if we open this up,
by clicking on the down-facing arrow,
we can see the name is listed in full here,
magazine_C in this case.
So that is now the temporary reference point for rotations.
And I could, for example, select this sofa group,
and we'll see that the Rotate Gizmo,
is oriented with that magazine,
and I can rotate around that magazine, okay.
I'll undo that.
If you want to use a group as the picked coordinate center,
then you'll probably need,
to select that group in a dialogue box,
rather than clicking on it in the viewport.
So just to illustrate, I'll go back up here,
to my Reference Coordinate Systems, and choose Pick.
But I don't want to click on this table, for example,
because I'll end up selecting one of the table objects,
rather than the table group,
which I know is oriented with the World,
and will give me predictable results.
So right now, before I pick anything,
I can actually use a keyboard shortcut,
which will launch a dialogue,
displaying all the objects that are visible in the scene.
And I can choose the group node explicitly,
from that dialogue.
And the keyboard shortcut,
that you need to memorize here, is "h".
This is really important.
You'll need to use this whenever it's impractical for you,
to click on an object in the viewport,
but you still need to select something,
and you'll use this select by name dialogue,
press the H key on your keyboard.
And it says, pick object.
And I can, for example, click on table group 001.
I've selected the group node,
not any member of the group.
Click pick, and now,
that is my temporary Reference Coordinate System Center.
So with table 001 selected,
and dolly back a little bit,
with Control + Alt and middle mouse,
select all those objects,
and with my rotate tool active,
I'm actually, oh, rotating around the other table.
I actually wanted table 002,
but that just illustrates,
that I need to know the names of my objects,
before I go any further,
but there you go.
That's how we use the Transform Coordinate Center Flyout,
and we can choose to rotate around pivots,
we can rotate around selections,
or we can rotate around,
any arbitrary Reference Coordinate System,
including an object in the scene.
And when we're in that third mode,
Reference Coordinate System,
we need to choose our center,
using the Reference Coordinate System pull down here.
All right. That's how to use Transform Coordinate Centers.