|By dcantor . March 22, 2013 . tutorials.|
Each model that has been loaded is represented by an actor in a scene. When a model is loaded, a new actor for that model is automatically created and added to the current scene.
Actors are designed to be lightweight representations of models.
Actors are represented in voxelent by the vxlActor class.
var actor = new vxlActor(model);
The constructor takes one parameter: the model the actor will represent.
An actor extracts model properties such as colors and textures. These properties are stored into the actor
material attribute . However, an actor does not copy geometric information such as
normals. This design allows to change individual settings for actors that could be sharing the same geometry, saving memory.
[diagram actor vs models goes here]
As we saw in the Scene tutorial, we can obtain references to actors currently being displayed through the scene management operations. We can also use the
getActor shortcut available in the public API:
var actor = vxl.api.getActor(a); //a can be the actor name or the actor UID.
As it can be seen in the public API page, these operation shorcuts can work with the current scene or with a scene passed as a parameter.
Let’s take a look at some of the basic actor operations:
An actor color can be change using the setColor method. This method internally changes the diffuse property of the
vxlMaterial object associated with the actor. Say for instance that we have an actor named cone in the current scene. Then to change its color we write:
var cone = vxl.c.scene.getActorByName('cone'); cone.setColor(0,1,0); // sets the cone color to green
Where the parameters correspond to the R, G and B color components in the [0,1] range. There are other properties that can be used to update the appearance of an actor. These will be discussed with detail in the tutorial about materials.
An actor can stop reacting to light sources by setting the shading property to
This is achieved by the
setShading operation. Using the same actor cone created in the previous section:
cone.setShading(false); // cone stops reacting to light sources; cone.setShading(true); // the cone starts reacting to light sources again;
An actor can be stop from being rendered by setting its visible property to false. This is done with the
cone.setVisible(false); // the cone is not rendered cone.setVisible(true); // the cone is rendered again
An actor location can be repositioned using the
setPosition property. For example, if we want to move the cone to the origin we would write something like this:
cone.setPosition(0,0,0); // vxlActor.setPosition(x,y,z);
On the other hand if we just want to translate the actor in relation to its current position we can use the
actor.translate(0,10,0); // translates the actor 10 units in the positive Y-axis direction (up).
We can rotate actors using the
rotateZ operations, which receive the angle in degrees (360):
cone.setPosition(0,0,0).rotateX(10).rotateZ(10); //rotate the actor 10 degrees in on the X axis, then it rotates 15 degrees on the Z axis.
The previous example shows that rotation and translation operations can be concatenated.
The scale of an actor can be changed using the
setScale method. This method receives one or three parameters. When using one parameter the scale will change equally in all the axes. Otherwise, when three parameters are used. The scale is changed for the x, y and z components independently:
cone.setScale(2);// the actor doubles its dimensions cone.setScale(1,2,1); // the actor doubles its height (y-component);
To obtain a complete reference of all the properties available to actors make sure of checking the vxlActor API page.