Animatie technieken voor vorm generatie

Using animation techniques for geometry generation.

These 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. 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. The animated snapshot 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.

The two techniques:

Animated snapshot.

• 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

Animated sweep.

• 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

Animated snapshot

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 to many frames can make it cumbersome to adjust the animation. When the animation duration is set the object or objects have to be keyed on the first frame. The object can be animated.

Use the animated snapshot

• Define the total amount of frames for the animation, with a min of 2 times the amount of copies to be made and a max of 10 times
• Select the object or objects
• Go to the first frame by sliding the mouse over the time line to the left
• Select the channels which have to be animated by clicking on the name of the channel ( becomes black)
• Right click and select Key Selected
• Change the current frame and change the object
• Key the change
• Select a next current frame and adjust the object again……..
• The object is animated
• Go to the pulldown selection menu and select animation
• Select Animate- Create Animation Snapshot- optionbox (cube)
• Set Time Range – defines which frames will be used for coping the object – use time line
• Set Increment – defines at which frames a copy is made – increment 1 means every frame a copy is made
• Set Update – fast – defines when the animated sweep is updated if the original animation is altered
• Apply

Animated sweep

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.

Use the animated sweep

• Define the total amount of frames for the animation, with a min of 2 times the amount of copies to be made and a max of 10 times
• Select the curve
• Go to the first frame by sliding the mouse over the time line to the left
• Select the channels which have to be animated by clicking on the name of the channel ( becomes black)
• Right click and select Key Selected
• Change the current frame and change the curve
• Key the change
• Select a next current frame and adjust the curve again……..
• The object is animated
• Go to the pulldown selection menu and select animation
• Select Animate- Create Animated Sweep- optionbox (cube)
• Set Time Range – defines which frames will be used for coping the object – use time line
• Set Time – defines at which frames a copy is made – increment 1 means every frame a copy is made
• Select geometry – Nurbs
• Apply

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, for example, 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.

How to use the path option

Define the correct amount of frames

• Select the object
• Go to the pulldown selection menu and select animation
• Select Animate-Motion Paths – Attach to motion paths- option box
• Set Time Range – defines which frames will be used for coping the object – use time line
• Set Follow – if the orientation of the object has to follow the curvature
• Front axis and Up axis – defines the orientation of the object with regard to the path- front is the orientation of the object when it follows the path – the axes is defined by the axis of the object. The up axis is the which axis of the object should point upwards
• The world up type defines the orientation of the axis along the path- if the objects flips during the animation choose a different option- scene up works well
• Apply
• The commands for the animated sweep and animated snapshot remain the same.

If you want to animate the rotation of the object when it moves along the path you will have to deselect the follow option. Only the translate channels are animated when de follow option is deselected. The rotation and scale option can now be animated by changing the value of the channel and setting a key.

Blend shapes

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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. 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. Alter the base shapes and connect them with the create Blend shape command to the target shape. A relation is created between the base and target shape. It is no possible to blend the target shape into an adjusted base shape during the animation, changing the shape of the object. This technique makes use of the shape of several objects.

How to use Blend shapes

• 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.

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.