Crystal Space 2.0.0: 4.15.6 Sequence Manager

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### 4.15.6 Sequence Manager

Written by Jorrit Tyberghein, jorrit.tyberghein@gmail.com. Last updated 16 August 2003.

When you define geometry in a map file this usually define a static representation of the world. Using the sequence manager it is possible to define specific events that trigger on certain conditions. Using these events (sequences) you can move or animate objects, control lights, fog, ....

The sequence manager is actually divided in two plugins. First there is the basic sequence manager itself. This is nothing more then a schedular that can schedule certain actions that should happen at certain times. Applications can use this sequence manager for their own purposes if they want.

On top of the sequence manager there runs the engine sequence manager. This plugin predefines several operations and triggers which make it a lot easier to do engine related things like moving objects, controlling lights, .... We will discuss mainly the engine sequence manager in this section.

A sequence represents a small script with commands that operate on objects in the world. A trigger represents a series of conditions which will cause the sequence to be executed. The important thing of the sequence manager is that it is very time based. Operations don't all execute at once but at specific times relative to the start of the sequence. Note that all times in the sequence manager are specified in milli-seconds.

#### Basic Example

The easiest way to explain the engine sequence manager is to look at a simple example as how it can be used from a map file:

    <world>
      ...
      <sector name="hall">
        <light name="roomlight">
          <center x="10" y="4" z="10" />
          <radius>20</radius>
          <color red="0" green="0" blue="0" />
          <dynamic />
        </light>
        ...
      </sector>
      ...
      <sequences>

        <sequence name="turn_on_light">
          <setlight light="roomlight" red="1" green="1" blue="1" />
          <delay time="50" />
          <setlight light="roomlight" red="0" green="0" blue="0" />
          <delay time="80" />
          <setlight light="roomlight" red="1" green="1" blue="1" />
        </sequence>

      </sequences>

      <triggers>

        <trigger name="trig_turn_on_light">
          <sectorvis sector="hall">
            <sphere x="10" y="4" z="10" radius="5" />
          </sectorvis>
          <fire delay="0" sequence="turn_on_light" />
        </trigger>

      </triggers>
    </world>

This is a simple example where we turn on a light as soon as we are in a certain radius of the light. Let's explain how it works. First we define a sequence which is called `‘turn_on_light’`. This sequence has three `‘setlight’` operations and two delays. Internally this is compiled to something which looks like this:

    time 0ms: setlight 'roomlight',1,1,1
    time 50ms: setlight 'roomlight',0,0,0
    time 130ms: setlight 'roomlight',1,1,1

Basically there are three operations here and the delays are only used to indicate when these operations are executed relative to the start of the entire sequence. So for example, if the sequence is fired at time 10050 then immediatelly at that point the first operation is executed. 50 milliseconds later the second operation is executed and finally, 130 milliseconds later the last operation is executed.

There are a few important observations to be made about this. First, as soon as a sequence is executed or fired ALL operations in that sequence will execute at the correct relative time no matter what happens otherwise. This also means that if you fire another sequence then that sequence will also get fired at the same time and depending on the relative timing of the operations some of those operations might happen at the same time.

Also note that there are operations that themselves have a duration. For example, there is a `‘fadelight’` operation which fades a light to some color. It has a `‘duration’` parameter. But this duration does NOT influence the relative timing in the sequence itself. So for example if you have this:

    <fadelight light="somelight" red="0" green="0" blue="0"
        duration="1000" />
    <fadelight light="somelight" red="1" green="1" blue="1"
        duration="1000" />

Then this will execute two fade operations on the same light at exactly the same time which is probably not what you want. This example is probably better written as:

    <fadelight light="somelight" red="0" green="0" blue="0"
        duration="1000" />
    <delay time="1000" />
    <fadelight light="somelight" red="1" green="1" blue="1"
        duration="1000" />

This will place the two operations at a time distance of 1000 milliseconds.

The reason that using `‘duration’` does not automatically advance the internal relative time is that it is sometimes useful to start several fade operations (or other operations that have a duration) at the same time. For example, two fade operations on two different lights.

A sequence as such is not useful. It needs to be fired at some point. You can fire sequences manually from code or you can define a trigger to fire the sequence if a certain condition is true. In this case we have a trigger which is called `‘trig_turn_on_light’`. This trigger will fire if the sector `‘hall’` is visible and the camera is in the sphere defined by the center `‘10,4,10’` and radius `‘5’`. As soon as this condition is valid the `‘turn_on_light’` sequence will be fired immediatelly. Note that this automatically implies that the trigger is disabled. This is to prevent the sequence from being fired several times while the trigger condition remains valid. If you want a trigger that keeps firing you have to re-enable it in the sequence.

#### Second Example

    <sequences>
        <sequence name="animlight">
            <fadelight light="l1" red="0" green="0" blue="0"
                duration="1000" />
            <delay time="1000" />
            <fadelight light="l1" red="1" green="1" blue="1"
                duration="1000" />
            <delay time="1000" />
            <fadelight light="l1" red="1" green="0" blue="0"
                duration="1000" />
            <delay time="1000" />
            <fadelight light="l1" red="0" green="1" blue="0"
                duration="1000" />
            <delay time="1000" />
            <fadelight light="l1" red="0" green="0" blue="1"
                duration="1000" />
            <delay time="1000" />
            <enable trigger="animlight" />
        </sequence>
    </sequences>
    <triggers>
        <trigger name="animlight">
            <sectorvis sector="large" />
            <fire sequence="animlight" />
        </trigger>
    </triggers>

In this example there is a trigger called `‘animlight’` that fires as soon as the sector named `‘large’` is visible. Here is what happens as soon as the condition of the trigger (in this case `‘sectorvis’`) is true:

1. First the firing of the trigger will cause the trigger itself to be disabled. This is to avoid the trigger firing again next frame.
2. Then the `‘animlight’` sequence will be executed. What this basically means is that all operations of that sequence are scheduled in the engine sequence manager at the appropriate times relative to the current time. The `‘delay’` operation in the sequence is responsible for tagging every operation with the specified time. So in this particular example six operations will be scheduled: five `‘fadelight’` operations (of which one is scheduled to execute immediatelly) and one `‘enable’` operation.
3. The first operation that is executed is `‘fadelight’`. This operation will fade the light color of the light named `‘l1’` from whatever color it has now to black. `‘l1’` must be a pseudo-dynamic light for this to work.
4. One second later (due to the `‘delay’`) the second `‘fadelight’` gets executed. And so on.
5. Finally the `‘enable’` operation will execute which means that the `‘animlight’` trigger is enabled again. If the `‘large’` sector is still visible this will cause the trigger to fire immediatelly again.

It is important to note that the `‘duration’` parameter that is given in some of the operations does NOT imply that the next operation will execute after that operation has finished. The `‘duration’` parameter has no effect on the internal relative time that is maintained for the sequence operations. To influence that you must use `‘delay’`.

#### Last Example: Using Parameters

If you want to use the same sequence for different lights you can use parameters like in the following example:

    <sequences>
        <sequence name="animlight">
            <args>
                <arg name="l" />
                <arg name="trig" />
            </args>
            <fadelight light_par="l" red="0" green="0" blue="0"
    	    duration="1000" />
            <delay time="1000" />
            <fadelight light_par="l" red="1" green="1" blue="1"
    	    duration="1000" />
            <delay time="1000" />
            <fadelight light_par="l" red="1" green="0" blue="0"
    	    duration="1000" />
            <delay time="1000" />
            <fadelight light_par="l" red="0" green="1" blue="0"
    	    duration="1000" />
            <delay time="1000" />
            <fadelight light_par="l" red="0" green="0" blue="1"
    	    duration="1000" />
            <delay time="1000" />
            <enable trigger_par="trig" />
        </sequence>
    </sequences>
    <triggers>
        <trigger name="animlight_l1">
            <sectorvis sector="large" />
            <fire sequence="animlight">
                <light name="l" light="l1" />
                <light name="trig" light="animlight_l1" />
            </fire>
        </trigger>
        <trigger name="animlight_l2">
            <sectorvis sector="large" />
            <fire sequence="animlight">
                <light name="l" light="l2" />
                <light name="trig" light="animlight_l2" />
            </fire>
        </trigger>
    </triggers>

Here you see how the same sequence (`‘animlight’`) is used by two different triggers for two different lights. It is not only the light that has to be given as a parameter but also the trigger that needs to be enabled again. That's why two parameters are used.

A lot more is possible here. I will give a short summary of all commands (that are not operations) that are supported in sequences here:

`args`

  Use this to enumerate all arguments to this sequence. You only have to specify the name of the arguments here.

`delay`

  Increase the relative time for following operations. The relative time starts at 0 in the beginning of the sequence. Using `‘delay’` you can increase relative time. If you don't use `‘delay’` between two consecutive operations then they will execute at the same time. You can use `‘delay’` with the `‘time’` parameter in which case a constant amount will be added. Or you can use `‘delay’` with the `‘min’` and `‘max’` parameters in which case a random amount between the two given values will be added. This amount is truely random in the sense that it will be reevaluated every time the sequence fires.

#### Supported Operations

Here is a list of all operations that you can use in a sequence. Note that every operation is tagged with a relative time (relative to the start of the sequence). If you want to use a parameter for an operation that uses an argument to the sequence then you have to add `‘_par’` to the parameter name like this: `‘light_par’`.

`run`

  This operation will run the given sequence. Parameter is `‘sequence’`.

`move`

  Move the specified object from the current position to the specified position in the given time (duration). Parameters are `‘mesh’`, `‘duration’`, `‘x’`, `‘y’` and `‘z’`.

`movelight`

  Exactly like `‘move’` operation, but working on lights. Accepts `‘light’` parameter with the light name.

`rotate`

  Rotate the specified object from the current orientation to the new orientation in the given time (duration). Parameters are `‘mesh’`, `‘duration’`, optionally `‘relative’` to make the operation relative to the object center, otherwise the pivot point with be the `‘v’` parameter. As children you can specify rotation matrix and vector using `‘rotx’`, `‘roty’`, `‘rotz’` and `‘v’`.

`rotatelight`

  Exactly like `‘rotate’` operation, but working on lights. Accepts `‘light’` parameter with the light name.

`material`

  Change the material on some object. Parameters are `‘mesh’`, `‘material’`, and optionally a `‘polygon’` parameter if you only want to change the material for one polygon.

`fadecolor`

  Fade the color of a mesh from the current value to the new value. This only works on some types of meshes. Parameters are `‘mesh’`, `‘red’`, `‘green’`, `‘blue’` and `‘duration’`.

`setcolor`

  Set the color of a mesh. This only works on some types of meshes. Parameters are `‘mesh’`, `‘red’`, `‘green’` and `‘blue’`.

`fadelight`

  Fade the color of a light from the current value to the new value. Parameters are `‘light’`, `‘red’`, `‘green’`, `‘blue’` and `‘duration’`.

`setlight`

  Set the color of a light. Parameters are `‘light’`, `‘red’`, `‘green’` and `‘blue’`.

`fadeambient`

  Fade the color of a dynamic ambient from the current value to the new value. Parameters are `‘sector’`, `‘red’`, `‘green’`, `‘blue’` and `‘duration’`.

`setambient`

  Set the color of dynamic ambient. Parameters are `‘sector’`, `‘red’`, `‘green’` and `‘blue’`.

`fadefog`

  Fade the color and density of fog from the current value to the new value. Parameters are `‘sector’`, `‘red’`, `‘green’`, `‘blue’`, `‘density’` and `‘duration’`.

`setfog`

  Set the color and density of fog. Parameters are `‘sector’`, `‘red’`, `‘green’`, `‘blue’` and `‘density’`.

`enable`

  Enable the given trigger. Parameter is `‘trigger’`.

`disable`

  Disable the given trigger. Parameter is `‘trigger’`.

`check`

  Enable checking of trigger state every `‘delay’` milliseconds (or disable if 0). Use this in combination with `‘test’` below. Parameters are `‘trigger’` and `‘delay’`.

`test`

  Test the stated of the given trigger and execute the right sequence depending on the result. For this to work you should use `‘check’` to enable testing of the trigger at regular times. Parameters are `‘trigger’`, `‘truesequence’` and `‘falsesequence’`. Both `‘truesequence’` and `‘falsesequence’` are optional. Warning! This operation does not cause the current sequence to stop. All operations that follow this test operation will still execute at their dedicated times regardless of the outcome of this test!

`setvar`

  Set a shared variable to some value. The only required parameter is `‘var’` which is the name of the variable you want to set. Then there are various other parameters that you can use to set the variable:

#### Supported Conditions

Here is a list of all conditions that are supported in a trigger:

`onclick`

  True when the given mesh is clicked on. Parameter is `‘mesh’`.

`lightvalue`

  True when the given light has a color which satisfies some condition. Parameters are `‘light’`, `‘operator’`, `‘red’`, `‘green’` and `‘blue’`. `‘operator’` can be `‘less’` or `‘greater’`.

`manual`

  For manual trigger (from application code). No parameters.

`sectorvis`

  True when the sector is visible. Parameter is `‘sector’`. There are also some optional children that this trigger supports:

`fire`

  This is not a trigger. It just indicates the sequence that will be executed when the trigger is valid. Parameters are `‘sequence’` and `‘delay’` (optional). In addition you can also specify parameters for the called sequence.

`disable`

  Normally a trigger is enabled by default. With this keyword you can disable the trigger initially and let some other sequence (or the application) enable the trigger.

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