1.2 - Querying and Setting Actions in a Pipeline Setting

Table of Contents

• 1.2.1 Host Side
• 1.2.2 IG Side

In a pipeline setting, (which may be a Host-IG configuration, or a DIS/HLA network), a DI-Guy user can be confronted with one or both of the following questions:

• I am running DI-Guy for constructive purposes on my host system. What is the best way to query DI-Guy to understand when an action has changed so that I can send it down the pipe?
• I am running DI-Guy for visualization purposes on my IG system. What is the best way to command new actions as they come down the pipe?

The following table shows the basic ways a DI-Guy character can have its action change on a host.

Ways that Actions can Change
Character Mode	The way the character has its action changed.	Visual Result
PATH	Character has action beads on the path.	Smooth, nice transitions.
PATH or FREE	set_desired_action()	Smooth, nice transitions, but action will start after current action loop is complete for maximum visual quality.
PATH or FREE	force_action(<action name>="">, DIGUY_DEFAULT_FLOAT, 1, 0.5f, …)	Smooth transition that starts immediately. Quality of transition is not as nice as set_desired_action() but typically is quite good.
PATH or FREE	force_action(<action name>="">, DIGUY_DEFAULT_FLOAT, 0, 0.0f, …)	Instant transition with discontinuity.

1.2.1 Host Side

The recommended way to handle the host side is to use the character callback function diguyCharacter::CALLBACK_ID_CURRENT_ACTION_CHANGED(). This function is called when a new action should be commanded down the pipe.

A less desirable approach is to create a string variable called previous_action for each character, and then at every time step:

• Query the character's actions using get_current_action() and get_desired_action().
• If the current_action equals the desired_action AND the current_action does not equal the previous_action:
  • If the current_action does not equal the desired action, send a new action packet with a smooth bit set to 1.
  • Otherwise, send a new action packet with a smooth bit set to 0.

1.2.2 IG Side

The recommended way to handle the IG side is to always call force_action() with the smooth bit determining whether to make the third and fourth arguments be (1, 0.5) or (0, 0).

Another way to do this is to use diguyMotionEngineSnapshot::get_motion_engine_snapshot(). This function returns a structure that tries to encode all the major variables that the motion engine is currently using to manage the primary action, and related transition values. The multi_channel example demonstrates this approach.

Note

We also recommend the use of a DI-Guy Guide using the drift or adaptive algorithm for each IG character if the IG does not receive position and orientation information every timestep. The guide_example, in ./programming_examples/opengl, shows how the guide can be used to best effect.

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