Extension

This article is about COLLADA extensions. For information on installed wiki extensions, see Special:Version.

COLLADA provides flexibility by allowing applications to define extensions to existing COLLADA elements. These extensions take the form of alternative <technique> elements, additive <extra> elements, and scalable <input> elements.

Extension by Alternative

COLLADA enables multiple representations of many elements. In such cases, the element is defined using one <technique_common> and zero or more <technique> elements. The common technique, which is required, is a strongly typed representation of the element.

Other techniques are defined by a vendor supplying an alternative representation. Each <technique> has a profile attribute that indicates the platform (product name or similar) to which the extension applies.

Each alternative representation of an extensible element should contain values that describe the element for that profile. The representations may have coherency among profiles, although that is not required. In other words, if <technique_common> describes an ambient light, it is valid if an alternative <technique> for that light describes something else, such as an area light for that profile.

Using <technique> to choose profiles

A COLLADA processor chooses one, and only one, of the available alternatives. It chooses either the <technique_common> or one of the <technique> elements. Where alternative choices are possible within the schema, the <technique> element models the alternative extensions. QUESTION: I don't follow the preceding highlighted sentence; isn't it just saying the same thing that was already said earlier? For example:

 <light>
  <technique_common>
    <ambient>
      <color/>
    </ambient>
  </technique_common>
  <technique profile="alternative_1">
    <ambient>
     <color/>
    </ambient>
  </technique>
  <technique profile="alternative_2">
     <foo />
  </technique>
 </list>

See also

• Portal:Extensions directory