Distortion/Displace

[Dankha]

Hello dear affiniters

I'm am trying to use the displace filter on affinity photo (BTW the live filter is totally broken but i will make a post in the right topic for that).
Here are some screenshots to show what i mean (zoomed in from original document).

Original photo :
Displacement map : 


Displace Sobel 3x3
 Displace Red/green : 

First question, why do i get a grainy/pixel displacement effect on the sobel 3x3 method ? And why does it only displace on a little area ? the whole gradient from the map does nothing ? i don't understand the use of this method ?

For the red/green method, if i understood it right, in affinity, the grey parts of the displace map does nothing, and the black goes down, and the white goes up. 
i really don't understand the purpose ?? for better use, it should be the amount of displacement, and not the direction right ?

I hope someone could help me with this questions, thank you very much for your time
(i'm sorry for my bad english, not my native langage)

-Anna

[NotMyFault]

Hi Anna,

the filter reacts on contrast inside the D-map, not on absolute values. For Soebel, only intensity of image is used, and the direction is derievend from the D-Map depending on contrast inside x and y axis.

for red/green, the given color channels are used to manage x and y axis shift.

 

A gradient shows minimal effect, except at the hard b/W edge as you notived.

For best results, use an image with high local contrast. E.g. by Emboss filter, tone map persona, highpass filter.

[NotMyFault]

33 minutes ago, Dankha said:

BTW the live filter is totally broken but i will make a post in the right topic for that)

Please don’t rush bug reports, and stay in the questions section until you had a change to fully understand how to use the filter. 

[Dankha]

Hey ! Thanks for the fast reply ! 

I still don't understand why i get the grainy look with the sobel method  
Could it be because the D-map isn't the same resolution as the project ? 

I understand a little bit better how the affinity displacement behaves, but it makes it pretty difficult to make glass effects like this :

  

[RobWu]

It works as expected. Maybe this helps:
 

and you need a slight variation on the displace image. No hard 'cuts' in the pattern.

[NotMyFault]

When switching from other apps to Affinity, better unlearn all about displacement filter, and carefully study the tutorials given by @RobWu. 
the key fact to remember: the displacement is perpendicular to the gradient / contrast of the map.

if you have a black to white edge horizontally, the filter moves pixels vertically.

[Dankha]

Thanks for the tutorials ! I will have a look and do some experiments
But i have already watched a bunch of tutorials and even with days of trying to replicate some effects (not from the tutorials, from other photos, (like the screen shot on my previous answer) i failed. 
I am very happy with the results of the displacement filter for effects like putting a design on a t shirt or the second tutorial you recommended. Maybe it is not "improvable" but just how it works and i can't get to the results i want. And that's ok, i just wanted to be sure.

21 hours ago, NotMyFault said:

When switching from other apps to Affinity, better unlearn all about displacement filter, and carefully study the tutorials given by @RobWu. 
the key fact to remember: the displacement is perpendicular to the gradient / contrast of the map.

if you have a black to white edge horizontally, the filter moves pixels vertically.

. I learned everything on Affinity, i do not come from adobe or other apps.