Joints
From ShadeCamp
Joints are used for moving or deforming shapes, mainly when you create animations. You can manipulate the joints as you do parts; when you create a joint, a joint part is created in the Browser.
If you place a shape inside this joint part, the shape will be affected by the joint. The joint can also include other joints, just like a part. If you make a Skin setting (described later), the control points of shapes or the vertices of polygon meshes will be affected by the joint even if the shape is not within the joint part.
Types of Joints
The types of joints and their functions are shown in the following table.
Joints are considered a type of part with interactivity, capable of providing special functions beyond those of normal parts. Manipulating joints can provide movement for and affect the state of objects included in or bound to the joints, thereby enabling you to create animation functions and movements.
Using Joints
With a few exceptions, joints are created, modified, and displayed in the Figure window, and their names and hierarchical structure are indicated in the Browser and the Motion window.
Bones
Joints other than Light joints and Morph joints have a parent-child hierarchy in which the center or the starting point of each joint will be connected with a straight line called a Bone, allowing you to visually grasp the hierarchical structure. The hierarchy of joints enables you to make complex animations and poses.
Animation
The state of an object can be set to follow the state of a joint. Object movements can be set by watching how those states change on a continuous axis of time called the “Sequence.” In an animation, before-andafter states of joints are set in frames called “key frames,” and the states at the in-between frames are interpolated, in order to render all the required frames. Settings related to a sequence are specified in the Motion window.
Simulating Movement and Posing
Joints are used for animations, as well as for simulating movement or posing. For example, machines with working parts can have joints on those parts, and by setting appropriate joint values, you can simulate various movements. Joints can also be used to adjust the pose of a human or animal model.
Current Mode and Sequence Mode
Manipulations with the Joint value slider in the Object Info window and the Motion setting window and Inverse Kinematics operations are equivalent to each other in the initial state. These operations are immediately reflected on objects in the Figure window, and that state is retained until similar operations are performed. This state is called the Current mode or the Current world.
Turning on the Sequence checkbox in the Motion window will retain results of further changes in joints in the sequence as motion key points. This state is called the Sequence mode or the Sequence world.
The position on the sequence where a motion key point is created is called a “key frame.” Objects in the Figure window are displayed by interpolating the states of joints between key frames, in accordance with the position of objects on the sequence. You can return to the Current mode by turning the Sequence checkbox off, and the Figure window will also return to the Current mode. The simulation of movement that we have described previously can be performed in the Current mode, but motion settings for animation will be made in the Sequence mode.
Editing Joints
Joints can be edited and transformed, just like other objects, at any time. For hierarchical joints, intuitive modification of all joints and objects included in the joints is possible using the Modify tool.
Joint Control Points
- Rotator joints have control points at the center of revolution and at both ends of the axis of revolution.
- Slider joints have control points at the starting point of movement, and at the moving distance in the positive direction.
- Scale joints have control points at the center of magnification/reduction and at the position which shows the direction.
- Uni-scale joints have control points at the center of equal magnification/reduction.
- Ball joints have control points at the center and on the path.
Manipulating Joints
Manipulation with the Joint value slider in the Object Info window and the Motion window, manipulation with the Motion box in the Motion window, and manipulation with Inverse Kinematics or reading in pose data will apply changes which correspond with respective manipulations on objects included in or bound to the applicable joint. The joint value range of any joint (except Ball joints) can be limited using the Joint value upper and lower limiters.
Resetting the Current Joint Value to the Default
The value of the Joint value slider in the Browser window is called the “current joint value.” Instead of using the Joint value slider, select the Object Selection box in the Browser window and click the right mouse button (Win) / click the Object Selection box in the Browser window while holding down the control key (Mac) and choose “Reset This Joint” or “Reset All Joints” to reset the current joint values to the initial (default) value.
Choosing “Reset This Joint” will reset the value of the selected joint; choosing “Reset All Joints” will reset the current joint values of all joints included in the selected part. When initial values are not within therange of the joint value upper and lower limiters, a value as close to the initial value as possible will be set.
Although Ball joints do not allow operations with the Joint value slider, the joint value can be reset to the initial value by turning on the checkbox at the bottom of the Current Joint value slider.
Inverse Kinematics
Inverse Kinematics can be used for Rotator, Slider, and Ball joints. Similar to the intuitive drag operations with the Move tool in the Figure window, manipulations with Inverse Kinematics can be applied to objects, and the values of joints in the upper hierarchy will also change in conjunction with the manipulation. Up to nine hierarchical levels of joints can be interlocked.
Parts and joints other than Rotator, Slider, and Ball joints are ignored, and will not be included in the number of hierarchy levels. When an object or a joint is selected, the names of the joints which can be interlocked are displayed in the area below the submenu of the Move tool in reverse order of the hierarchical structure, from which you can choose the level you wish to interlock.
Suppressing Inverse Kinematics
A joint will not be included in the Inverse Kinematics operations if a “%” character is added to the beginning of its name in the Browser.
Setting Joint Values by Loading Pose data
Loading pose data (using Import in the File menu) enables setting Current Joint values of multiple joints all at once. For any joints with the same names as those in the pose data, their joint values will all be set at the same time.
Applying Joint Manipulations to Objects
Joint manipulations are applied to attributes that are affected by the joint. For example, manipulating a Scale joint associated with an Area Light will change the area of the Area Light, but will not change the intensity.
When objects are bound to joints, joint manipulations will be applied to those objects. In such cases, the hierarchical structure of the objects is independent of the hierarchical structure of the joints.
When objects are included in joints, and those objects are not bound to any of the joints, joint manipulations will be applied to those objects. In this case, the hierarchical structure of the objects is dependent on the hierarchical structure of the joints.
When Flat is selected from the Joint pull-down menu in the Transformation Matrix dialog box, joint values will be reflected on next parts in addition to children. Place an object on which you wish to reflect a joint value in a next part hierarchy, to adjust the position of the joint without moving the object itself.
Line objects, curved surfaces, and Polygon Meshes allow you to apply a Bind setting to control points. When these objects are included in a joint, or when they are subject to a Flat Joint setting, and when some of the control points are bound to another joint, then joint manipulations which include that object or joint with the Flat Joint setting will be applied to the control points that are not bound. The Bind setting can be made in the Skin window.
Ignoring Parent Transformations
Joints are affected by transformations of all parts in the parent hierarchy.
For example, revolving a joint may magnify it in a certain direction, and consequently, if changes in joint values cause unexpected results, transformation of the parent hierarchy of that joint might be the cause. Therefore, this effect should be canceled. Whether or not this part has been transformed can be confirmed in the Transformation Matrix dialog box of the Object Info window. When the matrix has values other than the initial values (unit matrix), then that part has been transformed. In order to cancel the effect of the transformation, reset joint values to the defaults, then select an untransformed part, and create a new part. Move the created part to the same hierarchy as the transformed part (note that the parent part of this hierarchy -- that is, the transformed part -- is not transformed), and move the joint to that part. Surface attribute settings should also be changed as required. Delete the old part.
Creating Joints
Let’s practice moving an object using a joint.
1 Choose File menu / New File to open a new document.
2 Create a disk in the Front view, and convert it into an extruded object in the Top view, to create an extruded disk.
3 Choose Rotator from the Part tool and click at point A on the ruler to fix the Y axis position of the 3D cursor, then start dragging horizontally from point B in the Top view.
The dragged line becomes the axis of rotation and the disk shown in the vertical direction becomes the plane of rotation. In the Browser, a rotator joint part named “Rotator” is created.
4 In the Browser, drag the “Extruded Disk” inside the “Rotator.”
The extruded disk is now contained within the Rotator (rotator joint part), and will be affected by the rotator joint.
5 Choose View menu / Object Info to display the Object Info window and select the “Rotator” within the Browser.
The view of the Object Info window has changed and the joint value slider can now be used.
6 Move the Joint Value slider up and down.
You can see the shape revolve around the rotator joint as you move the slider.
Combining Joints
We will apply a combination of different types of joints to the existing shape.
1 Choose Slider from the Part tool / Slider (slider joint), and drag from the top surface of the extruded disk vertically within the Top view.
Drag horizontally from point A in the Top view. The dragged line becomes the slider axis. In the Browser, a slider joint part named “Slider” is created.
2 In the Browser, drag the “Rotator” part inside the “Slider”
The extruded disk is now contained within the Rotator (rotator joint part) and the Slider (slider joint part) parts, and will be affected by both the rotator joint and the slider joint.
3 Select the “Slider” within the Browser and move the Joint Value slider of the Object Info window up and down.
You can see the rotator joint and the extruded disk move along the slider joint as you move the Joint Value slider. The rotator joint is also contained inside the Slider (slider joint part) and will be affected by the slider joint.
4 Move the Joint Value sliders for the Slider and the Rotator to move the extruded disk.
As described above, creating a hierarchical structure with different kinds of joints allows you to add sophisticated motions to shapes.
Creating a Multi-Node Object
Using the existing shape, let’s create a multi-node object and move it freely.
1 Reset the Joint Value sliders for the Slider and the Rotator to 0.00 to restore the default settings.
To set a joint value, you can either move the slider, or click on the value displayed below it to activate it and directly type in the desired value, as shown in the figure.
Note: Typing a period (.) twice in succession resets the joint value to 0.00.
2 Select the “Rotator” in the Browser and choose Toolbox / COPY tool / Translate.
Drag the shape downward in the Top view, to make a copy of the shape with its joint axis aligned with the bottom of the original extruded disk.
3 Choose the Toolbox / repeat tool / 1 Time.
The rotator joint and shape are copied again at the same distance defined in the previous procedure.
4 In the Browser window, drag the Rotators (rotator joint parts) so that they have the parent/child relationships.
5 To recognize each joint easily, name the joints “Slider A”, “Rotator B”, “Rotator C”, and “Rotator D” respectively, from the top.
After setting the browser as shown in the above figure, let’s move the multi-node object.
Select each joint in turn, and try moving the Joint Value sliders.
6 When you select “Slider A” and move the slider, all the rotator joints and objects contained in “Slider A” will move together.
7 When you select “Rotator B” and move the slider, all the joints and objects contained in “Rotator B” rotate together.
8 Similarly, when you select “Rotator C” and move the slider, all the joints and objects contained in “Rotator C” rotate together.
9 And, when you select “Rotator D” and move the slider, all the joints and objects contained in “Rotator D” rotate together.
As described above, each joint will control the objects contained within the joint, according to the hierarchy shown in the Browser.
10 Restore the default settings by resetting each Joint Value slider to 0.00.
To quickly reset all joint values to 0.00, you can select the top-most joint in the Browser hierarchy with a Right click (Win) / control + click (Mac) to display the contextual menu, then select Reset All Joints, which resets all the joint values contained within the selected joint to 0.00.
Reset This Joint in the contextual menu resets just the selected joint to 0.00.
Setting Joint Values Intuitively
Now let’s use the inverse kinematics function to set the joint values intuitively. In inverse kinematics, joints lower in the hierarchy (or objects within the joints) affect those above them, to determine the movement (pose) of the objects by interconnecting all the joints.
1 Select the Extruded Disc at the bottom of the hierarchy.
2 Choose Toolbox / Move tool / Rotator B.
The Move tool menu lists the joint names (Rotator D, Rotator C, Rotator B, and Slider A, from the top).
These joints exist above the selected object in the hierarchy and their names appear in reverse order. By selecting Rotator B, the inverse kinematics function is applied to all joints (including Rotator B) contained within Rotator B.
3 Drag the selected object in the Side view of the Figure window.
The joint values of all joints contained in Rotator B are affected, and the motion (pose) of the object can be set. (Note that you can only drag the selected object once, immediately after choosing a joint in the Move tool.)
For joints grouped in the hierarchy, a combination of joint value settings for the joints is called a “pose.”
4 Choose Toolbox / Move tool / Slider A.
By selecting Slider A, the inverse kinematics function is applied to all joints (including Slider A) contained within Slider A.
5 Drag the selected object in the Side view of the Figure window.
Linear movement is added to the previous movement and the values of all the joints contained in Slider A are changed, allowing the movement (pose) of the object to be set.
As described above, the inverse kinematics function allows you to control how joints affect objects by selecting a particular joint in the Move tool of the Toolbox.
Using a Path Joint
This section describes the path joint. The path joint does not need a joint axis. If you choose Toolbox / Part tool / Path, a “Path” joint part is created in the Browser. When you place a line object above the Path joint part (a younger brother in the hierarchy) and place an object within the Path joint part, the object will move along the line object.
1 Choose File menu / New File to open a new document and create an open line object.
2 Choose Toolbox / Part tool / Path (path joint).
Place the cursor at the start point of the line object and create a sphere.
3 To create a sphere positioned at the start point, click point A on the Ruler to fix the Z- coordinate and create the sphere from point B in the Front view.
Since the control points forming the line object have their order, the first control point you create becomes a start point for the line object. If you select the line object and choose Toolbox / Modify tool / Reverse, the order of control point is revered for the selected line object. This operation transposes the positions of the start and end points for the line object.
4 In the Browser, place the line object above the Path joint (a younger brother in the hierarchy) and move the sphere within the Path joint.
5 Select the Path joint part in the Browser, and move the Joint Value slider of the Object Info window to check that the sphere moves along the line object.
For a joint value of 0.00, the sphere moves to the start point of the line object. For a joint value of 1.00, it moves to the end point of the line object.
Note: A path joint is associated with a single line object, which is positioned above the Path joint part in the Browser. You can position the line object above the Path joint part (a younger brother in the hierarchy) by dragging it.
The object moving along a path joint faces a fixed direction regardless of its position. To change the direction of the object moving along the path, you have to use a rotator joint as well.
Using a Morph Joint
This section describes the morph joint. A morph joint does not use a joint axis. If you choose Toolbox / Part tool / Morph, a joint part is created in the Browser. If two or more objects (curved surface, extruded object, revolved object, polygon mesh, and other base objects) with the same number of control points (or polygon mesh vertices) are contained within the Morph joint part, interpolation can be executed between the objects.
Even if very complex curved surfaces or polygon meshes are used, as long as the numbers of control points (or polygon mesh vertices) are the same, interpolation can be executed. However, you can never select a morphed image as a completed shape. You can also interpolate between different surface attributes by setting them for the shapes or parts contained in the Morph joint. Note that when objects or parts in the child layer within the morph joint part have only a base color as a surface attribute, the surface attribute will not be interpolated (morphed). If the surface attributes are to be interpolated using a Morph joint, at least one other parameter besides the base color must be set.
1 Open the Morph.shd file from the Chapter17 folder within the User Guide folder.
You will see two objects: a fish and a dolphin. These two shapes were created with curved surfaces having the same number of control points.
2 Choose Toolbox / Part tool / Morph (morph Joint).
In the Browser, a morph joint part whose name is “Morph” is created.
3 Place the Fish and the Dolphin inside the morph joint part.
Place the Fish above the Dolphin in this hierarchy.
4 When the morph joint part is selected, the joint value slider in the Object Info window becomes active, allowing you to adjust the joint value to 0.00 and render an image.
5 Adjust the joint value slider to 0.50 and render.
A shape somewhere between a Fish and a Dolphin is rendered.
6 Adjust the joint value slider to 1.00 and render.
The object, completely morphed from the Fish shape to the Dolphin shape, is rendered.
The values from 0.00 to 1.00 in the joint value slider correspond to the morphing of the object from the upper shape in the Morph joint part to the lower shape.
Using Ball Joints
Here you will create a shape like an arm, incorporate ball joints and Uni-Scale joints, and make a skin setting. You will also use inverse kinematics and make a setting for a motion in which the arm bends and the upper arm’s muscle bulges.
First, you will create an arm-like shape and incorporate ball joints and a Uni-Scale joint.
1 Choose File > New to create a new document.
2 Choose Open Line from the Create tool in the Toolbox, and create a line object from left to right within the Top view, as shown in the figure below.
You don’t have to create a shape exactly like that shown in the figure, but it has to have the same number of control points.
3 Choose Toolbox / solid tool / Revolve, click point A on the ruler to fix the 3D cursor Y-coordinate, and drag the mouse horizontally from point B within the Top view.
A revolved object is created.
4 Choose Convert to Curved Surface from the Convert tool to convert the revolved object to a curved surface.
An arm-like shape is created.
Next let’s incorporate ball joints and a Uni-Scale joint in this shape. Let’s make ball point settings for the places to be articulated.
5 Choose Toolbox / Part tool / Ball Joint and drag your mouse from point A within the Top view.
Note: If you hold down the Ctrl (Win) / option (Mac) and chose the Toolbox / Part tool / Ball Joint, you can continue to create ball joints, without having to choose Ball Joint in the Toolbox each time. When you are finished, click the finish button in the Toolbox, or press the Enter key.
6 Similarly, create ball joints at points B, C, and D.
Next, you will set the Uni-Scale joint to express the bulging muscle of the arm.
7 Choose Toolbox / Part tool / Uni-Scale (Uni-Scale joint) and drag your mouse from point E within the Top view.
8 In the Browser, move the Ball Joints and the Uni-Scale joint to arrange them in the hierarchy shown in the figure below.
Be careful with the position of the Uni-Scale joint.
When a joint is placed within another joint, a line appears to connect the starting points of the joints. The line is referred to as a “Bone.”
The line connecting the starting points of the joints is called a “Bone.”
This is used to check the joint hierarchy visually, and also affects the Skin setting (described later) where the distance between the Bone and the shape control points matters.
9 To easily recognize each joint, name the joints “Ball Joint A”, “Uni-Scale E”, “Ball Joint B”, “Ball Joint C”, and “Ball Joint D.”
All our joints are finished.
Skin Settings
Using the existing shape from the previous section, you will make a skin setting.
When you make a skin setting, the control points of shapes or the vertices of polygon meshes are affected by joints, even if such objects are not within any joint part. The skin setting is made in the Skin window. Let’s make the setting.
1 Choose View menu / Skin to open the Skin window.
2 Select the Curved Surface in the Browser.
The Skin window shows the settings for joints allocated to the control points contained in the selected curved surface. You have not yet made any settings, so “None” is displayed for each column.
3 Choose Toolbox / Modify tool / Enter Modify Mode, then choose Edit menu / Select All to make all the control points of the curved surface active.
All the numbers down the left side of the Skin window become active.
Note: These numbers are arranged according to the control points of the line objects. The numbers run from the starting point to the end point. In the case of a curved surface, after the control points of the line object listed at the top within the curved surface part in the Browser are numbered, the control points of the lower object lines are numbered.
4 Press the Bind button at the upper left corner of the Skin window.
Joints are automatically allocated to each active control point. This Bind function specifies the distance between the “Bone” line, which connects the starting points of the joints, and each control point, and then allocates proper joints automatically.
Here, you can see that “Uni-Scale E” has not been allocated to any of the control points.
The reason for this will be explained later in this chapter. For now, you will allocate Uni-Scale E to the proper control point manually.
5 In the Browser, check that the Curved Surface is selected, then choose Toolbox / Modify tool / Switch.
The Skin window display is switched.
The point numbers do not change. However, since the lines forming the curved surface were switched to thelines in the lateral direction, the control points of the lateral lines are now numbered from the starting point to the end point. The lateral lines forming the curved surface listed in the Browser are arranged from the top line to the bottom line. You can see the difference because the joints automatically allocated by the Bind function in step 4 above have hanged.
6 In the Browser, select a line object, as shown in the figure below.
The Skin window displays just the control points of the selected line object.
7 With the line object selected as shown in Figure 10, check that all the numbers at the left side of the Skin window are active, and select “Uni-Scale E” from any of the Joint pull-down menus.
“Uni-Scale E” is allocated to all the active control points. In the Skin window, the same setting is applied to all the active control points.
Even after the joint is allocated, it does not have any effect as long as the Weight slider value stays at “0.00.”
8 Adjust any of the Weight sliders next to the Joint pull-down menu to 1.00.
All the Weight sliders for the active control points move together.
To express the bulging muscle of the upper arm, you had better scale up/down the selected line object more in one direction, rather than equally.
9 Click to select Number “2” at the left side of the Skin window.
10 Click the numerical value displayed next to the Weight slider to make it active, then enter “2.00” directly.
Only this control point is affected by the Uni-Scale joint, twice as much as the other control points.
The Skin setting is finished.
Moving an Object with Skin
Using the existing shape from the previous page, let’s move the shape for which you set Skin.
To move the ball joints, use inverse kinematics.
1 In the Browser, select “Ball Joint D”.
2 While holding down the Ctrl (Win) / option (Mac), choose Toolbox / Move tool / Ball Joint A.
If you choose Toolbox / Move tool / Ball Joint A while holding down the Ctrl (Win) / option (Mac), you can operate inverse kinematics continuously without choosing Ball Joint A again. When you want to move on to another operation, click the finish button in the Toolbox, or press the Enter key.
3 Within the Top view of the Figure window, drag the selected “Ball Joint D”.
When you drag the mouse in the Top view, the connected joints move along the ZX plane.
4 Similarly, drag “Ball Joint D” within the Front view.
When you drag the mouse in the Front view, the connected joints move along the XY plane.
Thus, when an inverse kinematics drag is performed in the Top view, Front view, or Side view, it will move along the ZX plane, XY plane, or YZ plane.
This time, we want to twist the arm to skew it.
5 In the Browser, choose “Ball Joint B” and click the Local button in the Control Bar.
The Figure window display changes so that the axes of Ball Joint B are displayed parallel to the XYZ axes.
6 If the inverse kinematics is still selected, drag the mouse within the Top view. If it is not selected, rechoose Toolbox / Move tool / Ball Joint A, and drag.
7 When you finish dragging, click the Global button on the Control Bar.
The Figure window returns to the original (Global) coordinate system state.
Note: When you want to twist or skew a shape, display the target joint in the local coordinate system temporarily in order to move it more intuitively. When you finish moving it, it is a good idea to return to the global coordinate system.
Finally, let’s make the muscle of the upper arm bulge.
8 In the Browser, select “Uni-Scale E” and drag the Joint Value slider in the Object Info window to the right.
You can see that the point whose Weight slider value is set to 2.00 in the Skin setting is bulging twice as much as the other points.
As described above, the skin setting allows you to make joint settings for individual points (including control points and the vertices of a polygon mesh). Therefore, you can add more complex motions to a shape with this setting, rather than just placing shapes into joint parts.
Using Scope
Using the existing object from the previous section, let’s use the Scope function in the Skin window..
1 Select Ball Joint A and right click (Win) / control + click (Mac) in the Browser to display the contextual menu, then choose Reset All Joints to reset all joint values to 0.00.
2 In the Browser, select the topmost hierarchy (root part).
3 Choose Toolbox / Copy tool / Translate, then drag your mouse in the Top view, as shown in the figure below.
In the Browser, shape is copied and joints are added.
4 Now, change the names of the copied curved surface and ball joints to “Curved Surface AA”, “Ball Joint AA”, “Uni-Scale EE”, “Ball Joint BB”, “Ball Joint CC”, and “Ball Joint DD.” Also change the name of the original curved surface to “Curved Surface A”.
After making the above changes, the Browser should look like the figure above. In the following description, these shape and joint names will be used.
5 In the Browser, select “Ball Joint DD” contained in “Ball Joint AA”, choose the Toolbox / Move tool / Ball Joint AA.
6 Move “Ball Joint DD” in the Figure window.
The previously copied “Curved Surface AA” moves as a skin. If a shape with a Skin setting is duplicated together with its joints, the duplicated joints are applied to the skin setting of the duplicated shape.
7 Select “Ball Joint AA” and display the contextual menu by right click (Win) / control + click (Mac) in the Browser, and choose Reset All Joints to reset all joint values to 0.00.
Now you will use the Scope function in the Skin window to replace joints for which you made the Skin setting individually.
8 Select the topmost hierarchy in the Browser and choose Toolbox / Modify tool / Enter Modify Mode to make all control points active.
If they are not active, choose Edit menu / Select All to make all control points active.
9 Select “Curved Surface A” in the Browser.
10 The Clear button in the Skin window to set None for all the joints with the Skin setting.
11 Select Ball Joint AA from the Scope pull-down menu.
The Scope pull-down menu shows all joints in the hierarchy. You can select any joint to limit the joints to be bound to the joints contained in the selected joint hierarchy.
12 Click the Bind button.
The joints included in “Ball Joint AA” are allocated to the control points forming “Curved Surface A”.
13 Select “Ball Joint DD” in the Browser, choose the Toolbox / Move tool / Ball Joint AA, and then move the Ball Joint DD in the Figure window.
You can see that Curved Surface A is also Skin-set to the joints within Ball Joint AA.
14 Display the contextual menu and choose Reset All Joints to reset all joint values to 0.00.
Now, make a Skin setting for Curved Surface AA with Ball Joint A and the joints below it.
15 Select “Curved Surface AA” in the Browser.
16 Click the Clear button in the Skin window to set None for all the joints with the Skin setting.
17 Select “Ball Joint A” from the Scope pull-down menu and click the Bind button.
The joints included in Ball Joint A are allocated to the control points forming Curved Surface AA.
If you select the line object indicated in the figure below in the Browser, the Scope pull-down menu in the Skin window shows “> Ball Joint A”. This means that the Scope is set for the parent joint, i.e. Ball Joint A, and the line object inherits the Scope setting.
18 Select “Ball Joint D” in the Browser, choose Toolbox / Move tool / Ball Joint A.
19 Move Ball Joint D in the Figure window.
You can see that the joints contained in Ball Joint A are Skin-set for Curved Surface AA. The joints with the Skin setting for each curved surface have been replaced.
The Scope function allows you to allocate any joint hierarchy (among the groups of multiple joint hierarchies) to any shape, or allocate the same single hierarchy to multiple shapes.
Using Cameras
You can place multiple Cameras anywhere you want to in the Figure window, and switch the field of view freely using the Camera pull-down menu in the Camera window.
1 Open the Camera.shd file in the Chapter17 folder within the User Guide folder.
A cube and a sphere are arranged in this file.
2 Choose the Toolbox / Create tool / Camera, fix the Y-coordinate of the 3D cursor, and drag the mouse from point A in the Top view to create a Camera that faces the shapes.
When you create a Camera, you start dragging from the Eye Point, then release the mouse button at the Target Point.
3 Similarly, drag from point B in the Top view to create another Camera facing the side of the cube.
4 Move the 2nd Camera out of the 1st Camera, and name them “Camera A” and “Camera B”.
The perspective view shows the field of view seen from the Meta-camera.
5 If needed, open the Camera window using the View menu. If you choose “Camera A” from the Camera pull-down menu, the field of view is changed to that seen from Camera A.
6 Similarly, if you choose “Camera B” from the Camera pull-down menu, the field of view is changed to that seen from Camera B.
Additional Skin Information
The Skin window has several additional functions that we have not covered so far.
Setting multiple joints for a single point (control point or polygon mesh vertex)
In the Skin window, whenever you set a joint from a Joint pull-down menu, another Joint pull-down menu appears to the right. Multiple joints can affect a single point. Multiple joints bound to a point will increase the influence on that point.
The Weight Slider
Using the Weight slider, you can set the weight (amount of influence) of a joint. Normally, the range is 0.00 to 1.00. Figures 1 and 2 show an example of different Weight slider values.
You can click on the value displayed next to the Weight slider to activate it and directly type in a desired value beyond the range of 0.00 to 1.00.
The Bind function automatically sets this Weight slider as well.
The Bind Function
The Bind function determines the distance between the “Bone” line (that connects the starting points of the joints) and each control point, and then allocates optimal joints and weight values (influence values) automatically.
Now we will explain why Uni-Scale E was not allocated to any control points in the section on Making a Skin setting. The reason lies in the specification of the Bone, the line connecting the starting points of the joints. Refer to Figures 1 to 3.
For the joints incorporated into the arm shape shown in Figure 1, the Bone shown in Figure 3 was actually generated according to the Browser hierarchy shown in Figure 2.
Since the Bone was not generated for Ball Joint D and Uni-Scale E, the Bind function did not allocate them. To generate a Bone for Ball Joint D and Uni-Scale E, the joints should be included within each child part.
Joints are sometimes included in the lowermost child hierarchy (called “end joints” in some cases) intentionally to generate the Bone. In this example, Ball Joint D serves as an end joint. |
