Microsoft DirectX 8.0

PARAM Element

XML Reference

Specifies the value of a property on a transition, effect, or other subobject.

Example

<PARAM NAME="progress" VALUE="1.0" />

Attributes

Name Description Type
NAME Name of the property to set. String
VALUE Value the property has at time 0, relative to the start of the transition or effect. Use the AT or LINEAR element to specify the value after time 0. If the PARAM element contains no AT or LINEAR elements, the value specified by this attribute remains constant over the entire effect or transition. Depends on the property.

Parent/Child Information

Parent CLIP, EFFECT, TRANSITION
Children AT, LINEAR

Remarks

Many effects and transitions support properties that control various aspects of their behavior.

Most transitions support a standard Progress property that ranges from 0 to 1.0, indicating what percentage of the transition is reflected in the output. At Progress = 0.0, the transition is at the beginning of its sequence (entirely the first video image). At Progress = 0.5, the transition is half complete. (For example, in a wipe, at Progress = 0.5 the transition boundary is in the center of the image) At Progress = 1.0, the transition is complete (entirely the second image). By default, transitions go from Progress = 0.0 at the start of the transition to Progress = 1.0 at the end.

Other properties are usually specific to one particular transition or effect. For example, the wipe transition supports a GradientSize property that controls the width of the transition area. For more information about properties, see Transform Properties in the Microsoft® DirectX® Transform documentation.

You can set a property on a transition or effect by including a PARAM element. The VALUE attribute specifies the value of the property at time 0 (relative to the start of the transition or effect). If the PARAM element contains no children, the specified value remains constant over the duration of the transition or effect. To change the value over time, nest AT or LINEAR elements within the PARAM element. The AT element causes the property to jump directly from the old value to a new value at a specified time. The LINEAR element creates a smooth transition to a new value; DES interpolates the intermediate values.

In the following example, the Progress property starts at 0.0, jumps to 1.0 at time 2, and then makes a smooth progression back to 0.5 from time 2 to time 6.

<TRANSITION CLSID="{AF279B30-86EB-11D1-81BF-0000F87557DB}" START="0" STOP="6">
    <PARAM NAME="Progress" VALUE="0.0">
        <AT TIME="2" VALUE="1.0" />
        <LINEAR TIME="6" VALUE="0.5" />
    </PARAM>
</TRANSITION>

To run a transition backward, reverse the default behavior of the Progress property:

<TRANSITION CLSID="{AF279B30-86EB-11D1-81BF-0000F87557DB}" START="0" STOP="6">
    <PARAM NAME="Progress" VALUE="1.0">
        <LINEAR TIME="6" VALUE="0.0" />
    </PARAM>
</TRANSITION>