Torch effect like in Lone Survivor?

local name = "vignette"
shader_effects[name] = { shader = Shaders.vignette.Compiled }
shaderAddEffect(name)
shader_effects[name].num.u_resolution = {1920,1080}
shader_effects[name].num.vPos = {1920/2,1080/2}

varying vec2 uv;
uniform sampler2D texel;
uniform vec2 u_resolution;
uniform vec2 vPos;
void main ()
{
  vec4 color = texture2D(texel, uv);
  vec2 position = uv - vec2(0.5);           
  float dist = length(position * vec2(u_resolution.x/u_resolution.y, 1.0));

  float radius = 0.5;
  float softness = 0.09;
  float vignette = smoothstep(radius, radius - softness, dist);
  color.rgb = color.rgb - (1.0 - vignette);
  gl_FragColor = color;
}