Modify the shaders before compiling

onBeforeCompile.js

    this.material.onBeforeCompile = (shader) => {
      shader.uniforms.time = { value: 0 };
      shader.uniforms.texture = { value: texture };

      /******************** Vertex Shader ********************/

      shader.vertexShader = `
             #define TAU 6.28318530718
             uniform float time;
            
             attribute vec3 instPosition;
             attribute vec2 instUV;

             varying vec2 vInstUV;
        
             ${snoise3d}
             ${shader.vertexShader}`;

      const token = "#include <begin_vertex>";
      const customVertex = `
            vec3 offset = instPosition;
            offset.y = snoise( vec3( instPosition.xz * 6.0, time ) ) * 2.0;
      
            vec3 transformed = position + offset;

            vInstUV = instUV;
        `;

      shader.vertexShader = shader.vertexShader.replace(token, customVertex);

      /******************** Fragment Shader ********************/

      shader.fragmentShader = `
        uniform sampler2D texture;

        varying vec2 vInstUV;

        ${shader.fragmentShader}`;

      const token2 = "#include <dithering_fragment>";
      const customFragment = `
          vec2 instUV = vInstUV;

          vec4 color = texture2D(texture, instUV);

          gl_FragColor = color;
      `;

      shader.fragmentShader = shader.fragmentShader.replace(
        token2,
        customFragment
      );

      this.materialShader = shader;
    };