I have created many different extruded shapes in a scene with the example below being a simple extruded triangle, but I now need to create a radius along a single edge of the object.

So in the example I would like to create a radius along the edge of the extrude from 0,0 to 900,0

Does anyone have any ideas on how to achieve this?

function extrude(tex, gp){
  let PrtOBJ = [], PrtPTS = [];
  PrtPTS.push(new THREE.Vector2(0, 0));
  PrtPTS.push(new THREE.Vector2(900, 0));
  PrtPTS.push(new THREE.Vector2(0, 900));;
  PrtPTS.push(new THREE.Vector2(0, 0));
let Prt = new THREE.Shape(PrtPTS);
PrtOBJ.push(Prt);
let PrtEXT = {
    bevelEnabled: false,
    steps: 1,
    depth: 22,
    material: 0,
    extrudeMaterial: 1
};
let PrtGEO = new THREE.ExtrudeBufferGeometry(PrtOBJ, PrtEXT)
let PrtMAT = new THREE.MeshPhongMaterial({
    side: THREE.DoubleSide,
    map: tex
})
let PrtMesh = new THREE.Mesh(PrtGEO, PrtMAT);
gp.add(PrtMesh);

Looked through three and the only way I can see is to create the edge extrude as a separate object to give me this Screenshot

Is there a way to merge the two geometries together to ensure the texture maps correctly