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[Anark] Billboard (Physics Behavior)

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发表于 2011-10-15 10:54:00 |只看该作者 |倒序浏览

            Billboard (Physics Behavior)


         Summary


         Causes the parent object to always face the camera, with a variety of options.


            Category


            Latest Behaviors


            Author


            Gavin Kistner


            Difficulty


            (Reference)


            Time to Complete


            5 Minutes


         Downloads


         Click Here

         to download the associated files.


         (This document covers version 0.9.1 of the 'Billboard' behavior, current as of 2005-Feb-23)


         Description


         This behavior is primarily useful for simulating a 3D object by using an image map on a flat object, and causing that object to always face the camera as it or the camera moves.


         To cause the object to face the correct camera, you must choose the camera which will be rendering the layer with the object, using the

            Render Camera

         option. You may alternatively choose any other object, to cause the parent of this behavior to face that object.


         There are two types of billboarding available:


            Face Camera

            – the object rotates so that it is always facing the eye point of the camera. The object behaves like a small animal always watching a predator, even if the predator is walking past the animal without looking at it.





            Match Camera Rotation

            – the object rotates so that it always faces the same direction as the camera. (Also known as “side-of-the-road” billboarding; as the camera moves past the object, the object will behave like a billboard on the side of the road, showing its edge as the camera goes by. Flat and Depth Text objects use this type of billboarding.)


         For both types of billboarding, there is the option to either let the object rotate on all axes (the default) or to only rotate around the global y-axis by using the

            Y-Axis Only?

         property. For smoke and other particle effects, you likely will want to leave this unchecked. For cases where the object is sitting in the ground (such as a tree), you will want to check this property so that the object does not tilt forward and backward as the camera rises and falls.


         By default, this behavior assumes that the ‘front’ of the object is the negative Z side. You may use the

            Front Axis

         advanced property to change which local axis of the object should be rotated to face the camera.


         To cause particles created by the Particle Emitter behavior to billboard, attach this behavior

            to the Particle Emitter behavior itself

         .


         Basic Properties


            Render Camera


            The camera which will be rendering the scene.


            Billboard Type


            Always face the camera, or only match its rotation.


            Y-Axis Only?


            Only rotate the object about the global y-axis?


         Advanced Properties


            Front Axis


            The axis and direction that specifies the 'front' direction of the parent object.


            Start Immediately?


            Start immediately, or wait for the Enable action to be called?


         Actions


            Enable


            Begin keeping the parent object billboarded.


            Disable


            Stop rotating the parent object.


         Demonstration


            View Demonstration Project


            Download Project File