org.j3d.aviatrix3d.rendering
Interface CustomRenderable

All Superinterfaces:

java.lang.Comparable, Renderable

public interface CustomRenderable
extends Renderable

Marker interface for all leaf objects that wish to implement custom rendering capabilities beyond just the basic GL callbacks, combining the custom rendering of Cullable with the rendering callbacks of ComponentRenderable.

This interface is used by programmers that require fairly complex implementation logic at the point of rendering. An example of this is volume rendering that requires a set of viewpoint-specific cutting planes to be generated every frame. This is not achievable using the standard renderable interfaces as they have no way of determining the current viewpoint and transformation stack during the rendering process. This is made worse by a node that could have multiple parents, thus multiple transformation paths to it within a single cull traversal. A developer uses this class to take the given rendering information to generate a set of custom instructions that are passed back at rendering time, then later passed back during the rendering phase.

Assumable Preconditions

• All state required to render this node shall be already available. For example, if this is the geometry, all the appearance state will already be set in the pipeline.
• Any transformations provided by parent transformations will be already applied to the modelview stack.

Implementor Requirements

• This interface should only be implemented by classes that extend the Leaf base class. Anywhere else in the scene graph hierarchy will be ignored by the rendering system. Classes that want to be culled as part of a NodeComponent should make use of either ObjectRenderable or ComponentRenderable. Nodes further up the tree that provide grouping and structural information, should implement the Cullable interface.
• The methods must be re-entrant as they can be called from multiple places at once. For example, multiple pipes rendering the same object on different screens simultaneously.
• All state must be maintained within this class. It is assumed all rendering takes place within the render method and there is no post-render call. Thus any state that is changed should be restored by this implementation within the context of the rendering call.

Implementor Guidelines

Version:

$Revision: 2.2 $

Author:

Justin Couch

Method Summary

boolean	hasTransparency() Check to see if this renderable object has anything that could be interpreted as an alpha value.
boolean	processCull(RenderableInstructions output, javax.vecmath.Matrix4f vworldTx, javax.vecmath.Matrix4f viewTransform, javax.vecmath.Vector4f[] frustumPlanes, float angularRes) This node is being subjected to rendering, so process the provided data and return the instructions to the rendering system.
void	render(javax.media.opengl.GL gl, java.lang.Object externalData) Render object now using the pre-given set of custom rendering details.

Methods inherited from interface org.j3d.aviatrix3d.rendering.Renderable

equals

Methods inherited from interface java.lang.Comparable

compareTo

Method Detail

hasTransparency

boolean hasTransparency()

Check to see if this renderable object has anything that could be interpreted as an alpha value. For example a Raster with RGBA values or vertex geometry with 4-component colours for the vertices. Transparency information is needed for depth sorting during rendering.

processCull

boolean processCull(RenderableInstructions output,
                    javax.vecmath.Matrix4f vworldTx,
                    javax.vecmath.Matrix4f viewTransform,
                    javax.vecmath.Vector4f[] frustumPlanes,
                    float angularRes)

This node is being subjected to rendering, so process the provided data and return the instructions to the rendering system. If additional rendering instructions will be needed at the point that the render(GL, Object) method is called, then formulate that now, and hand it back as part of the query mechanism.

The culler will not make use of the children or numChildren variables as part of the rendering system. Only the return value of this method is used to determine if this object should be placed into the queue for sorting and rendering.

Parameters:

output - Fill in the cull information here

vworldTx - The transformation from the root of the scene to this node according to the current traversal path

viewTransform - The transformation from the root of the scene graph to the active viewpoint

frustumPlanes - Listing of frustum planes in the order: right, left, bottom, top, far, near

angularRes - Angular resolution of the screen, or 0 if not calculable from the available data.

Returns:

true if this should be rendered, false otherwise

render

void render(javax.media.opengl.GL gl,
            java.lang.Object externalData)

Render object now using the pre-given set of custom rendering details.

Parameters:

gl - The GL context to render with

externalData - Some implementation-specific external data to aid in the rendering that was generated in the processCull method.