ZBrushCentral

BPRimage of layer animation

I ha***65366;e some ploblems.
I tried to make a layer animation using ZBrush timeline.
First, I rendered a BPRimage at the first keyframe, then
rendered a BPRimage at the second keyframe. I did not change the position of the camera.
But the second image was not one as I expect.
The shadow of second image is same as that of the first image.
I imagine it is because of R2 feature, that ZBrush uses the old memory if
one makes the BPRimage, with the position of the camera not changed.
Please tell me how to solve the problem. Thank you in advance.