ActionScript3.0 - How to get color (uint) of pixel at coordinates? (Stage3D, Flare3D)

Question

Question is in the title:

[ActionScript3.0] How to get color (uint) of pixel at coordinates? (Stage3D, Flare3D)

I am using Flare3D library to render 3D scene on an iPad2. I need to get color values at 768 different coordinates every time screen is redrawn. Previously, on simple stage (2D), I could just draw it on 1x1 bitmaps translated to specified coordinates, now it does not work on stage3D. Plus, I am a bit worried weather it will kill the performance since I really need to do it as often as possible - actually every time screen is drawn. It would be really nice if that currently displayed screen was like a bitmap somewhere, so I could access it like simple array...but yeah, I am not holding my breath:)

Answer 1

Since Stage3D renders to back-buffer and one can't directly access it, you also need to render to BitmapData using Context3D.drawToBitmapData() method. Rendering to a bitmap is very slow, especially if the viewport is large. As you only need to access those 768 pixels, you could use Context3D.setScissorRectangle to render scene 768 times with the size of scissor rectangle set to 1x1 along with needed coordinates. I haven't tested that myself so I don't know if rendering scene 700 times won`t be slower than rendering it once, but you may want to try that. :)