private void allocateArrays(int nProjections, int projwidth, int projheight) {
		int projsize = projwidth*projheight;
		ColorModel cm = imp.getProcessor().getColorModel();
		if (isRGB) cm = null;
		stack2 = new ImageStack(projwidth, projheight, cm);
		projArray = new byte[projsize];
		for (int i=0; i<nProjections; i++)
			stack2.addSlice(null, new byte[projsize]);
		if ((projectionMethod==nearestPoint) || (opacity > 0))
			zBuffer = new short[projsize];		
		if ((opacity>0) && (projectionMethod!=nearestPoint))
 			opaArray = new byte[projsize];
		if ((projectionMethod==brightestPoint) && (depthCueInt<100)) {
			brightCueArray = new byte[projsize];
			cueZBuffer = new short[projsize];
		}
		if (projectionMethod==meanValue) {
			sumBuffer = new int[projsize];
			countBuffer = new short[projsize];
		}
	}