Displacement map limitation on ipad?

[DM1]

I am attempting to emulate a tutorial on displacement mapming performed with affinity Photo desktop, on my iPads Affinity Photo. 

Method. New canvas 2400x2400mm divided into 200x2400mm slices. Make first slice wth rectangle tool, add black to white gradient (tilt gradient slightly) and copy 12 times.

Finish with a 2400x2400 image comprising 12 x 200mm Gradients side by side. Simple so far.

 

Issue 1: Exporting this file takes ages and eventually produces a jpg file of over 280mb size. Attempting to reopen this jpg file crashes Affinity.

Issue 2: After placing an image in the original 'gradient map .afphoto file, any further actions 'appear' to lock up AP, though in realty I think  it is still working, just very very very slowly as the spinning gear is evident. Edit: still spinning 2hrs later 

 

Is this processing 'beyond' the iPads capability or is it a limitation/bug with Displacement filter and gradients in AP for iPad?

 

Here is a screen shot of the offending file.

 

[Alfred]

24 minutes ago, DM1 said:

Exporting this file takes ages and eventually produces a jpg file of over 280mb size.

 

Ouch! What are your export settings?

[DM1]

Realised my initial canvas setting converts to 2.4 metres x 2.4 metres.  Should have been 240mm x 240mm.  Working as expected when created at 'realstic' size. Gotta watch where I put those zeros!