BitmapMaterial :用于简单texture mapping
var earthMaterial:BitmapMaterial = new BitmapMaterial(Cast.bitmap(earthBitmap));
BitmapMaterial :使用 smooth (减少材质像素化 )和 precision (the texture should be correctly rendered to within 2 pixels )属性
var away3DMaterial:BitmapMaterial = new BitmapMaterial(Cast.bitmap(away3DBitmap), {smooth:true, precision:2});
TransformBitmapMaterial :可以用于平铺材质 (tile image)
var tiledAway3DMaterial:TransformBitmapMaterial = new TransformBitmapMaterial(Cast.bitmap(away3DBitmap), {repeat:true, scaleX:.5, scaleY:.5});
repeat 必须 设置为 true ,不然没有效果