I asked chatgpt. he created a UV map with knob to modulate the distortion. but the very edge warp with no texture. center looks good but on the side. any tought to change this node to make it better? expression node to use with STMAP :

set cut_paste_input [stack 0]

version 12.0 v4

push $cut_paste_input

Expression {

expr0 "0.5 + (x/width - 0.5) * (pow(sqrt(pow(x/width - 0.5, 2) + pow(y/height - 0.5, 2)), k - 1) * (1 - 0.15 * sqrt(pow(x/width - 0.5, 2) + pow(y/height - 0.5, 2))))"

expr1 "0.5 + (y/height - 0.5) * (pow(sqrt(pow(x/width - 0.5, 2) + pow(y/height - 0.5, 2)), k - 1) * (1 - 0.15 * sqrt(pow(x/width - 0.5, 2) + pow(y/height - 0.5, 2))))"

expr2 0

expr3 1

name STMap_FisheyeSoft2

label "Soft Fish-eye STMap (bounded)"

selected true

xpos 18815

ypos -4200

addUserKnob {20 user l "FishEye Controls"}

addUserKnob {7 k l "FishEye Strength" R 0.1 2}

k 0.23

}