RenderScript ScriptGroups - getting Output from script global in second Kernel

Question

I want to combine two Renderscript scripts into a scriptGroup. The first one is the ScriptIntrinsicBlur. Based on the blurred U8 allocation as input the second script calculates two things: gradient and gradient-direction. The latter is the formal out-Allocation of the second kernel. The first one is a global allocation filled via rsSetElementAt_float(). Now, I find this second allocation is returned empty after execution of the scriptGroup.

Question: Is my assumption correct that with a scriptGroup you cannot use script globals - or at least not change them via rsSetElementAt_(...)?

UPDATE: I realized that the performance gain by using U8 both as output of the ScriptIntrinsicBlur and as input of the proprietary kernel is already more than satisfactory, even in a simple sequential set-up of both scripts. This is primarily because it avoids to copyTo the ScriptIntrinsicBlur's out-Allocation first into a Java-array before passing it as a separate input-allocation to the 2nd kernel.

Before, I used U8_4 (ie Bitmap equivalent) as output of ScriptIntrinsicBlur, and then converted it to a one-dimensional greyscale int[] array, before passing it as in-Allocation to the proprietary kernel... Now I convert to greyscale byte[] (ie U8) already before entering the allocation into ScriptIntrinsicBlur and use U8 also as input for the 2nd kernel.

This is what I realize again and again when working with RS: it is really worth to simplify data flows to the extent possible, the speed gains are fantastic. (maybe I will check the Scriptgroup question at a later stage, as for now I am happy with the result).

Answer 1

There should be no issue with using a script global like this. It's not as efficient as the output allocation, but is possible. You mentioned the out allocation is empty, what are you seeing in the script global?