Let’s talk about elementary transformations again:
- Key G – Move the object
- Key R – Rotate it
- Key S – Resize it (Scale)
After initiating each of these transformations using the G R S keys, you can bind them to the x y or z axes by pressing X, Y or Z afterwards. For example, pressing the R key followed by Z will initiate object rotation around the z axis, which can be done by moving the cursor in a circular motion on the screen. By default, the orientation of the transformation is the same as that set for the 3D View: in the case of Global, pressing Z twice will change the orientation to Local, and vice versa. On the other hand, starting transformations using the respective icons in the toolbar will allow you to differentiate the orientation from that of the 3D View directly from the header using the selector:
In addition to binding transformations along the main axes, we can type the intensity of the transformation itself using the keyboard; for example, if we wanted to rotate an object around the z axis by 45 degrees, we would type the sequence R>Z>45 on the keyboard. Now we are able to understand that the vectors described in the previous paragraph, the ones that appear on the object when clicking on the Move icon are manipulators for direct interaction with the objects displayed in the Viewport. By acting directly on them, we can move the object along their respective axes.
In addition to the vectors, three tiny colored planes are depicted (red plane zy orthogonal to x, green plane zx orthogonal to y, blue plane xy orthogonal to z); clicking on these icons allows you to bind movement along the three aforementioned planes.
The rotation manipulators are three orthogonal circles (red, green and blue) that allow you to rotate the object around the main axes according to the orientation system of the selected transformations.
The outer white circle allows you to perform rotations around the axis directed to the point of view. By clicking inside the white circle (but within the ideal sphere defined by the three colored circles) and holding down the left mouse button, the pointer will become and you can perform rotations that are no longer bound to just one of the three axes, the result of which will depend on the angle of the point of view.
The Scale transformation manipulators are instead three segments with a small cube at the end.
In this case as well, it is possible to bind the transformations to the planes orthogonal to the x y and z directions. To perform precise translations, rotations or scale changes of any object (Global system) we can use the Transform panel located in the Item tab of the Sidebar menu that appears/disappears to the right of the 3D View when pressing the N key.
Here we also find buttons with the icon of a lock to make the corresponding value no longer subject to further transformations. In many circumstances it will be useful to continuously press the Shift key after initiating the transformation (also through the manipulators) in order to obtain smaller changes in relation to mouse movements. The Shift key will maintain the same fine adjustment function for each of the bars you will encounter in the various Blender menus related to any type of parameter (such as those visible in the previous image). Each object has its own origin point represented by the circle (which appears when the object is selected) whose position is fundamental for the outcome of the transformations just seen. In addition, Blender assigns the object a position in 3D space whose coordinates are those of its origin. The position of the origin can be changed in the Object Context Menu -> Set Origin where we find five options.
We start with the most important Origin to Geometry with which the origin will be fixed at the midpoint of the set of vertices that make up the 3D object (geometric center). Since during modeling (Chapter 2) we will make various modifications to the models, perhaps starting from the elementary forms of the primitives, it will be necessary to finally reset the origin by bringing it to coincide with the geometric center of the obtained model.
Geometry to Origin does not change the position of the origin, but that of the object so that its midpoint coincides with the current position of the origin. With Origin to 3D Cursor, the origin of the object becomes the position (arbitrary) of the 3D cursor.
Origin to Center of Mass (Surface) fixes the origin at the geometric center, which will coincide with the further option Origin to Center of Mass (Volume) unless the object is made up of separate parts or areas with a higher concentration of vertices.
Let’s start again from the default scene and position ourselves in the top-ortho view with the cube selected. Pressing the R key will initiate a rotation around the Z axis passing through the origin. Then, from the Origin menu, we set the origin at the position of the 3D Cursor that we placed away from the cube. Repeating the previous rotation, we will see the cube rotate around the Z axis passing through the 3D cursor this time.
This happens because the transformations refer to a Pivot Point that Blender considers the midpoint, in 3D space, of the origins of all selected objects by default, and therefore in this case the pivot point coincides with the origin of the only selected object. If, for example, it becomes necessary to perform a Rotate transformation on multiple selected objects, wishing for a rotation like the one seen previously, that is, around a point of choice in space where we will have placed our cursor, it will be enough to indicate the 3D Cursor as the pivot of the transformation in the Pivot Point menu. By clicking the icon in the 3D View header, we can set the pivot point between:
- Active Element:
The pivot will be the origin of the active element (distinguishable by the amber-colored outline).
- Median Point
(default setting): The pivot will be halfway between the origins of two objects, or in a position that will be the average of the values of the coordinates (xyz) of all the origins of the selected objects.
- Individual Origins:
Each object will have its own origin as a pivot.
- 3D Cursor:
The position of the cursor (as mentioned earlier).
- Bounding Box Center:
The equivalent of the median point but referring to the centroids of the parallelepipeds (Bounding Box) that contain the objects.
You can realize how important the pivot point position is during transformations, even with the simple scaling of any primitive, such as a cone.
If you start scaling (S) and constraint the transformation to the Z axis, you will see that the base and the vertex of the cone will move away or closer in equal measure from the origin, which, as a pivot, will remain fixed in space for rotate and scale transformations.
You will certainly find yourself preferring a change in dimensions relative to a different point, such as the vertex of the cone; in this case, simply place the 3D cursor on the vertex in the correct ortho view (at the desired level of precision) and then choose the 3D Cursor as the pivot point. The scale type manipulators will then be positioned on the vertex of the cone and, by starting the transformation, the dimensions of the object will vary while keeping the position of the vertex fixed.
The other feature of Blender that you will quickly become familiar with is that the “strength” of Scale or Rotate transformations, initiated via the S and R keys, is inversely proportional to the distance on the screen, between the pointer and the origin, at the moment the transformation is activated.
By pressing the S key with the mouse pointer very close to the transformation pivot, for example the center of the object, subsequent mouse movements will result in larger variations and vice versa. During the Scale transformation you will see a black dashed line appear connecting the pivot and the pointer; the two arrows at its end indicate that by moving the pointer towards the pivot position, the object will be reduced in size, while moving the pointer away from the pivot, the object will increase in size. The length of the dashed line is inversely proportional to the strength of the transformation and depends on the distance between the pointer and the pivot at the time the S key is pressed, as mentioned earlier. A dashed line also appears for the Rotate transformation, this time with two arrows indicating to rotate the mouse pointer clockwise or counterclockwise.
Regardless of the series of transformations made on an object in object mode, we can undo them through the Clear options in the Object menu in the 3D View header, thus restoring the initial position, rotation, and/or size as well as the position of the origin. To make the transformations final, resetting the rotation, position, and scale values listed in the Transform panel in the Item tab (key N), simply go to the Apply options in the Object menu, which will also appear on the screen with the Ctrl-A combination.
Wishing you an enjoyable and productive study with Blender, I would like to remind you that you can support this project in two ways: by making a small donation through PayPal or by purchasing the professionally formatted and optimized for tablet viewing PDF version on Lulu.com