billboard 贴图

将Billboard贴图加入3D 识别系统中，可以增强很多简单的非3D模型就可以实现的应用技术。但是和3D模型拥有一样的

大小变化和坐标变化。基于一张图片，无法旋转。

这是   Bart Wttewaall-5  写的  billboard 因为 Pv3d不存在这样的 类

package org.papervision3d.objects.special {

/**
* @author    Bart Wttewaall
* @website www.mediamonkey.nl
* @date    05-10-2008
* @version    1.0
*/

import org.papervision3d.core.proto.CameraObject3D;
import org.papervision3d.core.proto.MaterialObject3D;
import org.papervision3d.core.render.data.RenderSessionData;
import org.papervision3d.objects.DisplayObject3D;
import org.papervision3d.objects.primitives.Plane;

/**
* To do:
* .    override any rotation/pitch methods that can mess up the billboard?
*      or add transform matrix to calculation
*/

public class Billboard extends DisplayObject3D {

public static const toDegrees    :Number = 180/Math.PI;

public var plane                isplayObject3D;

protected var initialWidth        :Number;
protected var initialHeight        :Number;
protected var _width            :Number;
protected var _height            :Number;
protected var _segmentsW        :uint;
protected var _segmentsH        :uint;

// —- getters & setters —-

override public function get material():MaterialObject3D {
return super.material;
}

override public function set material(value:MaterialObject3D):void {
super.material = value;

if (plane.material != value) {
setChildMaterial(plane, material);
}
}

public function get width():Number {
return _width;
}

public function set width(value:Numb
er):void {
if (_width != value) {
// setting scale is faster then redrawing plane
plane.scaleX = value/initialWidth;
_width = value;
}
}

public function get height():Number {
return _height;
}

public function set height(value:Number):void {
if (_height != value) {
// setting scale is faster then redrawing plane
plane.scaleY = value/initialHeight;
plane.y = value/2;
_height = value;
}
}

public function get segmentsW():uint {
return _segmentsW;
}

public function set segmentsW(value:uint):void {
if (_segmentsW != value) {
_segmentsW = value;
redrawPlane();
}
}

public function get segmentsH():uint {
return _segmentsH;
}

public function set segmentsH(value:uint):void {
if (_segmentsH != value) {
_segmentsH = value;
redrawPlane();
}
}

// —- constructor —-

public function Billboard(material:MaterialObject3D, width:Number=100, height:Number=100, segmentsW:uint=0, segmentsH:uint=0) {
super();

initialWidth = _width = width;
initialHeight = _height = height;

redrawPlane();

// this will auto update the plane’s rotationY through calculateScreenCoords
autoCalcScreenCoords = true;
}

style=”font-family: courier new,monospace;”>
public function redrawPlane():void {
if (plane) removeChild(plane);

initialWidth = _width;
initialHeight = _height;
plane = new Plane(material, _width, _height, _segmentsW, _segmentsH);
plane.y = _height/2;
addChild(plane);
}

override public function calculateScreenCoords(camera:CameraObject3D):void {
super.calculateScreenCoords(camera);
faceCamera(camera);
}

/**
* This method isn’t foolproof: rotating this object will mess up the caculation
* todo: add transform matrix to calculation
*/
public function faceCamera(camera:CameraObject3D):void {
var dx:Number = camera.x – this.x;
var dz:Number = camera.z – this.z;
plane.rotationY = Math.atan2(dx, dz) * toDegrees + 180;
}
}
}

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