MIME: Using Displacements

The PlayStation's ability to use MIME objects and displacement animation opens up new worlds for animators. This chapter contains a brief tutorial which illustrates how you can use these capabilities in your own animations.

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Creating and Animating MIME Objects

This type of animation is good for objects that "squash" or "stretch," that should change shape when a button on the game controller is pressed.

For example, if you were animating a driving game, and wanted the car to "flatten" out when you pressed a button, you'd probably want to use a MIME object for the car, since you'd likely use displacements to animate the change in the car's shape.

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Creating the Animation

Figure 3.1 Creating a MIME object animation

Create your Object

For this tutorial, create a cube and call it "cube".

Define any Displacements

3. (SHIFT-L) on the cube to select it.

4. (CLICK-L) on Make Displacement.

5. Make an Absolute displacement for the object.

Since this will be the base displacement for our cube, let's name the displacement base.

6. After you've specified a name, (CLICK-L) on Save Displacement State.

7. Displace the object to a pose you want to associate with one of the buttons on the game controller.

For example, we can scale the object along an axis, simulating a "squashed" appearance.

9. (SHIFT-L) on the Cube to select it.

10. (CLICK-L) on Axis Scale.

11. (CLICK-L) on Y to scale along that axis.

12. (CLICK-L) on Object Midpoint.

Move the mouse left and right until the cube is squashed:

13. (SHIFT-L) on the cube again.

14. (CLICK-L) on Make Displacement.

15. Make a Relative displacement for the object.

Give the displacement a recognizable name-we'll use squash for this tutorial. Leave Source set to Previous state and State set to base. (This means that the current displacement is measured from a previous state named base-the base displacement we defined in step 5.)

16. After you've specified a name, (CLICK-L) on Save Displacement State.

You've now set up the basic elements needed to create a MIME object. Displacements are described in more detail in the N-Geometry Reference Guide.

Figure 3.6 The N-Dynamics script editor

18. (CLICK-L) on the Script button.

If there's a script already in the script editor, choose Create New Script. Either way, the Create New Script dialog box appears:

19. Name the script, and specify 2 channels.

Give script a name that embodies it's function, e.g. PSX-test.

Your new script appears in the Script Editor.

The two blue bars spanning the Script Editor window are script channels. Channels contain parameter data which controls the behavior of objects over time in an N-Dynamics animation.

The Edit Action Properties menu appears. Use this menu to define the behavior of each channel in the script.

22. (CLICK-L) in the Operation text box.

The Dynamic Operations menu appears. This menu is divided into several sections, Each section contains a number of classes, which in turn contain individual dynamic operations.

23. (CLICK-L) on Shape in the Geometry section of the menu.

Another menu appears, listing Shape operations:

24. (CLICK-L) on the Displace Shape [Template] operation.

25. (CLICK-L) on Cube when the list of objects in N-Geometry is displayed.

Figure 3.12 Selecting an object

26. (CLICK-L) on "squash" when the list of relative displacements is displayed.

Figure 3.13 Selecting a displacement

27. (CLICK-L) on Do It to select "squash."

28. (CLICK-L) on "base" when the list of initial states is displayed, then (CLICK-L) on Do It.

Figure 3.14 Selecting the initial state

29. In the Edit Action Properties menu, (CLICK-L) on Do It.

The Displace Shape channel in your script now contains two subchannels:

• Set Shape: base
• Multiple Displace Shape Cube

Figure 3.15 The Displace Shape template creates the channels needed to animate displacements

30. (CLICK-L) on the triangle in the upper right corner of the Multiple Displace Shape Cube channel.

This exposes the curve channel for the Multiple Displace operation.

31. (CLICK-L) on the black triangle in the [SQUASH] (LINEAR) curve channel.

This exposes the data inside the curve channel (including the location of any cues in the curve). Right now, the curve is linear, because we haven't defined any action yet.

32. Move the cursor over the middle of the channel and press "s" on the keyboard to insert or "set" a new cue.

There are always cues at the start and end of a channel. By default, these are associated with the base displacement defined for the object.

Because you've only defined one relative displacement for this object, only one curve channel is created; if you add more displacements (described below in the section "Adding Displacements," on page 3-20, additional curve channels are created for each selected displacement).

A Dynamics slider appears. You'll use sliders to control parameter values.

34. Move the slider back and forth until the value is approximately 1.0.

This parameter essentially tells Dynamics how far to move between the base displacement and the relative displacement. A value of 1.0 means "go all the way". Note that the cube is displaced in the Geometry window. You can use the Geometry display to interactively select a value for this parameter, if you chose.

The curve changes shape to show that the cue now has a value associated with it:

You're ready to animate your script.

Animate the Script

The cube starts in its base state, then squashes as it approaches the middle of the script, then returns to its base state as it approaches the cue at the end of the animation.

Your animation is played back in real time in the playback window.

39. (CLICK-L) in the Operations>Sony MIME Animation in the Dynamics section of the menu.

The Edit Action Properties menu for Sony MIME Animation appears:

40. (CLICK-L) on Do It in the Edit Action Properties dialog box.

Note in the script editor that there is now an Action Editor channel and a curve channel called [NUMBER1] (LINEAR):

41. Insert a cue in the MIME Animation channel at the same frame as the cue in the Multiple Displace Shape Cube channel.

Your script should look something like this:

Note that the cues in both channels are aligned with each other.

Create a new MIME Object in the Vector Editor

Figure 3.24 The Vector Editor

43. (CLICK-L) on Create>Create New MIME Object

44. (CLICK-L) on the cube in the object list which appears.

The name of the newly created object appears next to the Current MIME Object: field:

#<MIME-object Cube >

Create a New Action in the Action Editor

47. (CLICK-L) on Dyna>Action Generate.

If you're sure you want to convert the script, (CLICK-L) on OK. (Your N-Dynamics script is not affected.)

The script animates at each cue specified in the Action Editor.

For each cue in the Action Editor curve channel, a vector and wave are generated. Each of these vector/wave combinations is referred to as a subaction:

48. Turn off the subactions that correspond to the cues at the beginning and end of the channel, since they are the same as the base vector (displayed at the top of the Action Editor window.

To toggle a subaction on or off, (CLICK-L) on the check box next to it. A red check mark indicates that the subaction is active. Only the middle subaction should be active.

50. (CLICK-L) on Triangulate.

Figure 3.27 Cube with triangulated faces

Animate using Vector and Wave Data

The cube is animated in the N-Geometry window using the vector and wave data in the Action Editor.

The animation is played back in the MIMED Playback window.

If you want to add additional displacements to the object:

53. Open N-Geometry.

54. Choose Points in the Element sensitivity menu.

55. (SHIFT-L) on a vertex in the cube.

We'll move the vertex, creating a different shape.

57. Move the vertex until you've achieved a distinct look.

Figure 3.28 Our new displacement

58. (SHIFT-L) on the cube.

59. (CLICK-L) on Make Displacement.

Make another relative displacement, like you did in steps 14 through 16. Call the displacement pointy. Make sure you base the displacement on a previous state, called base.

61. (CLICK-L) on Create>Create New Vector.

62. In the dialog box that appears, name the vector.

It's usually a good idea to name the vector some variation of the displacement on which it's based. Let's use pointy:

63. (CLICK-L) on Do It.

64. (CLICK-L) on the base displacement that this relative displacement is based upon:

Figure 3.30 Choosing an initial displacement state

Choose base since that's the name of the absolute displacement we defined earlier in N-Geometry.

Choose pointy. You can create a vector that is based on multiple displacements; for now, let's work with just a single displacement.

67. Make sure the N-Geometry window is open.

68. Adjust the vector by moving the slider in the Vector Editor window left and right.

The object is update each time you let up on the slider.

69. Slide the value to 1.00.

70. Under Save, (CLICK-L) on Save Current Vector.

This saves the new vector.

72. Under Subaction, (CLICK-L) on Create Subaction.

A list of vectors that the vector editor knows about appears.

Choose pointy.

A list of waves for other subactions in the action is displayed. Choose
MIME-Sample: 01 for this example; you can edit the value of the wave later.

The new subaction appears below all the other current subactions in the action editor.

The cube animates again, using the vector and wave data in the Action Editor; note now that both displacements are active.

You have now created a MIME object that can be downloaded to the Sony PlayStation and manipulate using the game controller.

Remember that only the first four subactions can be associated with buttons on the game controller; make sure that those four subactions are at the top of the list in the Action Editor. You can use the Reorder Subaction command under the Subaction menu to change the order of the subactions in the Action Editor.

Setting up the PC to Receive the Animation Data

77. On the PC, execute the following commands to start the PSX software.

cd c:\psx

psx

When the software starts, a list of datasets that can be animated is displayed.

79. Enter the name for the new dataset at the prompt.

DATASET: cube-test

The dataset is added to the list of MIME objects.

The following commands are displayed:

Current DATASET: cube-test

1) Execute MIME-DATASET

2) Execute 		MIME-DATASET with WAVE-file

3) Playback TOD file

4) link/filt

5) Recv. files

6) QUIT

Please Input Number:

This command starts the PC telnet application, and places the PC in FTP Server mode, where it can receive data sent over from the SGI.

83. In The Action Editor, (CLICK-L) on Convert>Convert and Send Action.

(CLICK-L) on the action you want to convert from the pop-up menu which appears:

84. In the dialog which appears, enter a directory for the Action Editor to write temporary files.

During the conversion process, the Action Editor writes several temporary files to the specified directory. It's a good idea to specify the /tmp directory, or a subdirectory of /tmp, so that these temporary files will be deleted the next time you reboot your SGI.

85. When you (CLICK-L) on Done, the data are sent to the PC.

Files are sent to the Action Editor Host specified in the N-Dynamics Options menu. When all the files have been sent the following prompt is displayed on the PC:

Finished sending data.

(For more information about what files are written with the Convert and Send Action command, see "Convert and Send Action," on page 6-8. Other convert options are also described in the section"Convert," on page 6-8.)

The PSX menu appears again on the PC.

This is the format required for the PSX development kit.

Each of the first four vectors sent is associated with one of the buttons on the front of the game controller.

You can use the PlayStation game controller to animate your object in real time across the range of it's MIME displacements.

Note: Option 2 in the PSX menu, Execute MIME dataset with WAV file, plays your animation in a static loop. Use this option when you want to see your animation played back repeatedly. You cannot interact with these types of animations.

Exiting the PSX Program

90. Press "Q" to exit completely from the PSX software.

Saving your Work

Saving your N-Dynamics Script

92. (CLICK-L) on File>Save Script.

Specify the directory in which you want to save your script and any objects it may reference. For more on saving scripts, see the N-Dynamics Reference Guide.

Copyright © 1996, Nichimen Graphics Corporation. All rights reserved.