Blackmagic Forum

Hi,
I am faced with either a problem using DR or a bug:

I'm in a 3d plane and I want to move around an element. At first, no problem (project creation): the object's center of gravity is used to rotate around it, but after several modifications, including the object's pivot (I don't know if this is the cause of my problem), the selected object's center of gravity is ignored and rotation in the 3D plane is performed from an invisible point outside my 3D element zone. The distances covered by the macOS TrackPad during rotation are too great for me to focus on the selected element.

I restarted DR and this didn't solve my problem.

1- Is this bug known?
2- Is there a shortcut to recenter the rotation point of the 3D plane on the center of gravity of the selected object?
3- Is there a shortcut / trick to automatically place the pivot (transform node) at the center of gravity of the 3D element (text, shape)?

Pretty much every 3D element in fusion is it own mini scene, and there is a center 0.0 coordinates by default. A Pivot point is the point around which an object rotates. I am not sure which control is giving you trouble, but here is a list of the main controls and a short tutorial, so hopefully you will find what you want there.

Pivot and target are the main controls you want to look at for "center of gravity", but keep in mind that if you add transform 3D or merge 3D you can keep rotating scene around its "center of gravity" while the other elements can rotate around there, allowing you to create complex animations. but you can use target to be always at the center, which it is by default. Unless you change it.

Many tools in the 3D category include a Transform tab used to position, rotate, and scale the object in 3D space.

Translation

X, Y, Z Offset

These controls can be used to position the 3D element.

Rotation

Rotation Order

Use these buttons to select which order is used to apply rotation along each axis of the object. For example, XYZ would apply the rotation to the X axis first, followed by the Y axis and then finally the Z axis.

X, Y, Z Rotation

Use these controls to rotate the object around its pivot point. If the Use Target checkbox is selected, then the rotation is relative to the position of the target; otherwise, the global axis is used.
Pivot

X, Y, Z Pivot

A Pivot point is the point around which an object rotates. Normally, an object rotates around its own center, which is considered to be a pivot of 0,0,0. These controls can be used to offset the pivot from the center.

Scale

X, Y, Z Scale

If the Lock X/Y/Z checkbox is checked, a single Scale slider is shown. This adjusts the overall size of the object. If the Lock checkbox is unchecked, individual X, Y, and Z sliders are displayed to allow individual scaling in each dimension. Note: If the Lock checkbox is checked, scaling of individual dimensions is not possible, even when dragging specific axes of the Transformation Widget in scale mode.


Use Target

Selecting the Use Target checkbox enables a set of controls for positioning an XYZ target. When target is enabled, the object always rotates to face the target. The rotation of the object becomes relative to the target.

Onscreen Transformation Controls

Most of the controls in the Transform tab are represented in the viewer with onscreen controls for transformation, rotation, and scaling. To change the mode of the onscreen controls, select one of the three buttons in the toolbar in the upper left of the viewer. The modes can also be toggled using the keyboard shortcut Q for translation, W for rotation, and E for scaling. In all three modes, individual axes of the control may be dragged to affect just that axis, or the center of the control may be dragged to affect all three axes.

Courseware 103 - Introduction to 3D Space

Thanks KrunoSmithy but in my case it seems to be really a bug.

1 and 2 -> I don't know why, or how, but clicking on “Fit” (first choice) in the Zoom drop-down menu at the top left of the 3D plane view resets the center of gravity of the global rotation of the 3D plane.

3 -> Unfortunately the tutorial doesn't tell me if shortcuts exist to automatically put the pivot of 3d element to its gravity center.
I can't understand the use of “pick...” in the Transform3D node. Should the 3D plane view be focused on the object only? When I select “pick..” and target my object, I can only estimate the center of gravity, but it will never be exact!

Artenis wrote:Thanks KrunoSmithy but in my case it seems to be really a bug.

1 and 2 -> I don't know why, or how, but clicking on “Fit” (first choice) in the Zoom drop-down menu at the top left of the 3D plane view resets the center of gravity of the global rotation of the 3D plane.

There is no "center of gravity" per se, there are coordinate system numbers. 0.0 is the center of the scene by default, and than you move in XYZ from that point. As the post I made explains, you can move where pivot point is in relations to 0.0 and similar thing can be done with target.

Scale to fit option helps locate a 3D object in a scene, regardless of the pivot point.

Artenis wrote:3 -> Unfortunately the tutorial doesn't tell me if shortcuts exist to automatically put the pivot of 3d element to its gravity center.

Just reset the numbers to 0.0 by double clicking on the label of the slider. or enter 0.0 in XYZ coordinates.

Artenis wrote:I can't understand the use of “pick...” in the Transform3D node. Should the 3D plane view be focused on the object only? When I select “pick..” and target my object, I can only estimate the center of gravity, but it will never be exact!

Like I said, you use coordinates system numbers. If you to make it dynamic so that one object reactors to the other and they are not at 0.0, you can link them together by variety of methods. Either by using common transform tool ,like Transform 3D or Merge 3D and move them at the same time, or you can click on single parameter of the object, choose publish, and than in another object you want linked you choose "connect to..." and you like to what you just published. You can also use expressions and in some cases modifiers.

Its hard for me to follow what you know or don't know, but seems to me like you are struggling with the fundamentals of navigation in fusion. I don't think there are such bugs you claim. Unless you can demonstrate a particular bug, its probably related to your struggle with how navigation and the functions I mention work in fusion.

I've just found what's causing the problem (for me) of losing the center of rotation of the 3D plane:
As soon as I zoom to the negative level of the 3D plane (under the x-axis grid) and rotate, the center of rotation of the 3D scene changes.
I have to click on “Fit” in the “scale” drop-down menu of the view.