Modeling with animation techniques

Animation techniques can be used to generate geometry. The main methods are the Animated Snapshot and the Animated Sweep. Both work on the same principle however have a different result and therefore application. If we animate an object we change an object over time. Both methods of geometry generation use these two components of time and change as a basis of geometry generation. Both methods make copies at regular intervals in time of the animated object as it changes trough time.

Animated snapshot

It makes snapshots of the object as it changes trough time, hence the animated snapshot. It is basically an array of objects with the main difference that the object changes during the array and the direction of the array is depending on movement of the animated object.

• Similar to an array
• More complex arrays are possible as the object changes over time and the path can be defined by the user
• Smooth transitions of the objects as they are the result of the intermediate frame definition of the keys
• History makes it possible to change the animated snapshot after it is generated

If we use animation techniques for geometry generation we have to change an object over time. The first thing to do is to define the amount of frames in the animation. The amount is not directly coupled to the possibility to the amount of snapshot copies we make but it can make it easier to define interval of copies. Good practice is to keep the amount of frames a minimum of twice the amount of copies. The more frames the more control you have in later adjusting the copies. However too many frames can make it cumbersome to adjust the animation.

An example

1. 
   Define the total amount of frames for the animation. Set it by changing the end time of the animation
   
   
2. Select the object(s)
   
   
3. 
   Go to the first frame by sliding the mouse over the time line to the left
   
   
4. 
   Press s to key the first frame. All channels in the channel box become pink
   
   
5. Go to the last defined frame by sliding the mouse over the time line
   
   
6. 
   Change the position of the object(s)
   
   
7. Press s to key your last frame. All channels in the channel box become pink
   
   
8. Test your animation by sliding your mouse between frame 1 and your last frame. Your object(s) should move between the first and last position
   
   
9. 
   In the pulldown menu-set Animation go to Animation » Create Animation Snapshot and choose the option box
   • Set Time Range on Time Slider as you will animate between frame 1 and your last frame
   • Set Increment depending on your increment
   • Click on Snapshot to make the copies

The result is 6 different copies changing over time from its first position till its last position.

Animated sweep

The animated sweep has an additional feature which sets it apart from the animated snapshot. The animated sweep makes copies of animated curves and lofts a surface between them. So the principle is similar but due the extra step of lofting it generates a single surface defined by the animated curves. This last option is regularly used in blob architecture where the surface of an object is based on an animated curve driven by a complex set of properties and variables.

• Combination of the animated snapshot and a loft
• Makes it possible to make a loft of different curves while having a higher control over the path of the loft
• Used to array curves only
• Makes it possible to generate complex surfaces
• History makes it possible to change the animated sweep after it is generated

Like the animated snapshot the animated sweep depends on the object, in this case a curve, to change over time. As the curve is changed over time the corresponding section of the loft will change. Keep in mind that the animated sweep is used to generate a single surface out of the "snapshots" of the animated curve. The steps to generate an animated sweep are almost the same as the animated snapshot.

An example

1. Define the total amount of frames for the animation by changing the end time of the animation
   
   
2. 
   Select the curve
   
   
3. Go to the first frame by sliding the mouse over the time line to the left
   
   
4. Press s to key the first frame. All channels in the channel box become pink
   
   
5. 
   Go to the next or last defined frame by sliding the mouse over the time line
   
   
6. Change the position of the curve and transform the curve with scale and/or rotate
   
   
7. Press s to key the current frame. All channels in the channel box become pink
   
   
8. Continue if this is your last frame, otherwise repeat steps 5, 6 and 7
   
   
9. Test your animation by sliding your mouse between frame 1 and your last frame. Your curve should move between the first and last position
   
   
10. 
    From the Animation menu-set go to Animation » Create Animated Sweep and choose the option box
    • Set Time Range on Time Slider as you will animate between frame 1 and your last frame
    • Set a value at By Time depending on your increment
    • Click on Anim Sweep to create a loft with an animated sweep
      
      

Using paths in the animation to gain more control

The problem with setting transform keys by hand is that the accuracy is often not high enough to snapshot an object along an existing geometry. The vertical window frames are a good example. If the façade has a curved shape the window frame should closely follow the contour of the façade. This is very hard to animate by hand however there is an option to let the object follow a path during the animation. In this case the manual transform is replaced by the transformation over the path. This option makes it a very powerful tool in generating geometry along complex shaped curves or surfaces. Or to generate very accurately complex surfaces with the use of animated sweep.

Using a path with animated snapshot

To prevent unexpected behaviour of your to be animated object, follow these steps first:

• Make sure you know the position of the pivot point of the object. The pivot is the basis
• Use Modify » Freeze Transformations to set the transformations to 'zero'

1. Define the total amount of frames for the animation
   
   
2. Select the object and the path (curve)
   
   
3. 
   From the Animation menu-set go to Animation » Motion Paths » Attach to Motion Path and choose the option box
   • Set Time Range on Time Slider as you will animate between frame 1 and your last frame
   • Use Follow if the object has to follow the curvature of the path
   • Set the front of your object with Front axis
   • Set the top of your object with Up axis (standard is Y)
   • World up type defines the orientation of the axis along the path. If the objects flip during the animation choose Scene up
   • Click Attach to attach the object at the path
     
     
4. Test your animation by sliding your mouse between frame 1 and your last frame. Your object should follow the path between the first and last position
   
   
5. Finally go to Animation » Create Animation Snapshot to create the snapshots along a path

If you want to animate the rotation of the object when it moves along the path you will have to uncheck Follow. Only the translate channels are animated when Follow option is unchecked. Rotation and scale can now be animated by changing the value of the channel(s) and setting its key(s) at defined frames.

Using a path with animated sweep

It's similar to using a path with animated snaphot. The first steps are the same, but with extra steps at the end.

1. Define the total amount of frames for the animation. Change standard value 48.00 to your number of frames if needed
   
   
2. Select first the curved object and then the path (curve)
   
   
3. From the Animation menu-set go to Animation » Motion Paths » Attach to Motion Path and choose the option box
   • Set Time Range on Time Slider as you will animate between frame 1 and your last frame
   • Use Follow if the object has to follow the curvature of the path
   • Set the front of your object with Front axis
   • Set the top of your object with Up axis (standard is Y)
   • World up type defines the orientation of the axis along the path. If the objects flip during the animation choose Scene up
   • Click Attach. Your curved object is now at the beginning of your path.
     
     
4. Test your animation by sliding your mouse between frame 1 and your last frame. Your curved object should follow the path between the first and last position
   
   
5. Go to Animation » Create Animated Sweep and make sure to set the increment at By Time to 1

Blend shapes

One problem with attaching an object to a path and animating the channels of the object, is the limitation of possibilities of adjusting the geometry on a component level during animation. Although we can scale and rotate the object along a path, components of the object are not accessible for animation in the channel box.

Maya and most other animation software use a technique called blending for very accurate animation of the shape of the object itself. The technique is based on the premises that it can animate between the different positions of vertices of different objects and translate that animation to the components of the object attached to the path.
The effect will be that the shape attached to the path will try to mimic the shape of the adjusted geometry. This mimicking or blending is a powerful tool in generating complex shape change during animation.

How to use Blend shapes

To be sure the animation of the components will work it is necessary that the amount of components (vertices) is similar to the target object which is attached to the path. To make sure it will work copy the target shape and alter the copies. The target and base shapes have the same amount of vertices.

• Attach the target shape ( original shape) to the path
• Copy the target shape several times depending how many shapes the target object hat to mimic.
• Alter the base shapes ( copied objects)
• Select all the base shapes and the target shape, make sure the target shape is selected last.
• Go to the animate pulldown menu
• Select Create deformers – Create blendshape – default settings will work
• Nothing happens – that is correct because the amount of mimicking or blending is default set on 0
• To get acces to the amount of blending open Window- Animation Editors_Blendshape
• The menu provides you with sliders to change the amount of blending and keys to key the value of blending
• Select a current frame and adjust the amount of blending and key all the shapes
• Continue with this process
• If you are finished in animating the shape create the animated sweep or if you adjusted object use the animated snapshot
• Altering the base shapes will alter the animated sweep giving additional control over the final shape

To delete the blendshape connection press delete in the Blendshape menu.

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Application

This technique for blending is used by several architects when complex relations and propositions are connected to time related variables like sound, light and movement of objects. By scripting or making a direct connection between a variety of relations, propositions and the design driven variables the shape generation is automated and often unpredictable due to the complexity of the relations. In this case a variety of shapes are predefined according to the architectural interpretation of the possible values generated by the complex relations. An alternative approach is to use the method in combination with the history as a powerful design tool. Defining the path and possible sections and then use the history to not only adjust the sections interactively but also the path and the position of the sections with the help of the Graph editor.