Killing 3D Transforms

Here’s a quick tip. If you’ve ever dealt with 3D in Flash Player 10+ you’ll know that DisplayObjects in 3D in Flash Player are bitmap-cached; only the bitmap representation is transformed in 3D. Recently I was working on a site where objects landed on the stage, but after landing, they appeared really muddy, which was obvious when you looked at the text they contained. Even though they were completely flat, they were still using bitmap proxies! Not great.

Turning a DisplayObject into a 3D DisplayObject is as simple as assigning a value to its rotationX, rotationY, rotationZ, or z properties. But how do you turn it back? I tried giving all these properties a value of 0, but after their animations completed they were already 0. An object at z=0 still renders in 3D, using bitmap caching. Setting these values to NaN was no better.

The solution I found is to null out the 3D transformation matrix and assign a 2D transformation matrix. This can be accomplished like so for a DisplayObject named sprite:

var matrix:Matrix = new Matrix();
matrix.translate(sprite.x, sprite.y);
matrix.rotate(sprite.rotationZ);
sprite.transform.matrix3D = null;
sprite.transform.matrix = matrix;

In this code I simply drop the transformations that are inapplicable to 2D space. This is fine when your object is already coplanar with the stage.

Anyway, quick tip if this ever had you scratching your head too.