Curved gradients

[avukosa]

Hi all, 

I am Affinity user for sometime now. 

I know this question has been on for sometime, but no definitive answer. 

Specifically, my problem is if I have a curved shape and I want to add lighting which is tracking it along it's curvature.

Like for example I want to selectively lighten the Highway loop middle part and I want this lighting to follow the that curved loop. The lighting must be from the neutral exposure image underneath the underexposed.  

With straight objects this is fairly simple, I will add a mask layer to an underexposed image, which is on top of neutral image. Next, I will be using gradients on mask (normally Black and White) as they are giving smooth transitions between layers and are extremely helpful. 

I have tried with vector objects, drawing pen, rasterizing to mask, but so far nothing works. 

Any suggestion??  

 

thanks

[firstdefence]

Got a visual example?

Also which Affinity app/s do you have at your disposal?

...and finally which Operating System are you on, this helps with keystrokes etc

[avukosa]

1 hour ago, firstdefence said:

Got a visual example?

Also which Affinity app/s do you have at your disposal?

...and finally which Operating System are you on, this helps with keystrokes etc

Hi, Appreciate the answer. 
I am using Desktop Affinity photo for OSX, 

What I need the light to propagate evenly on the curvature. 

Attached is screenshot of two layers, black over white. Imagine underexposed to overexposed image. Painting black on mask exposes the overexposed image underneath. For exposing such, I am using gradients to whenever I can. 
On the left of that image I have linear gradient (obvious one) with three white-black-white points, and when dealing with straight architecture lines I use those to evenly spread light, or conical or whatever gradient is offered and suits me at the time.
However when I have curvature, like on the right of this example *made by brush and looks pretty bad, I am struggling, maybe I am missing something and something similar is possible indeed.