PixiJS - Fragment to add a gap and also a mask in projection with 3 walls of 1920x1200 each.

wall-mapping.frag

// 3 walls using each a 1920x1200 projector in a row but wall1 and wall2 collided as per projector physical placement
// so need to have a gap, as wall2 only uses 1866px so from x: 1920 (end wall1) to x:1974 (beginning wall2) we need 
// to shift all pixels by 54px
// Also discard all pixels that cover the pillar area where another projector will be used with a cone mapping to play
// content on loop.

precision mediump float;

// supplied by pixijs
varying vec2 vTextureCoord;
varying vec2 vFilterCoord;
uniform sampler2D uSampler;
uniform vec4 inputPixel;

uniform float gapx1;
uniform float gapx2;
uniform float pillarx1;
uniform float pillarx2;

float gapLen = gapx2 - gapx1; // in pixels

void main ()
{
  vec2 coords = vTextureCoord.xy;
  vec4 color;
  float x = vTextureCoord.x * inputPixel.x;
  float normGap = gapLen / inputPixel.x;

  // Shift pixels based on the gap between wall1 and wall2 projections
  // to blend the image properly
  if (x <= gapx1) {
    color = texture2D(uSampler, coords);
  } else if (x > gapx1 && x <= gapx2) {
    color = vec4(0.0);
  } else {
    // deduct the gapLen
    coords.x -= normGap;
    color = texture2D(uSampler, coords);
  }

  // discar pixels between pillar area as there will be another
  // projection mapping with a looping video at the exhibition
  if (x >= pillarx1 && x <= pillarx2) {
    discard;
  }

  gl_FragColor = color;
}