private Vector3 RenderPixel(Scene scene, int screenX, int screenY, float dX, float dY, int pictureHeight, int pictureWidth) { var viewportX = (screenX + dX)/pictureWidth*2 - 1; // Screen Y is pointed down var viewportY = 1 - (screenY + dY)/pictureHeight*2; return scene.SampleColor(viewportX, viewportY, 4); }