THREEJS: Depth order between Mesh object with shader material (with volume rendering) and other mesh objects is always wrong

Question

I'm using Threejs to create a medical-volume-rendering app. I'm using a shadermaterial to define the volume rendering of a body and for the single rois (region of interest) and other extern objects I'm using basic or phong-materials with defined geometries. Unfortunately the volume rendering object is always behind the other objects, the depth order is ignored... I've tried to change the setting of many parameters like trasparent, depthWrite fragDepth-Extension etc...

Can anyone help me? Many Thanks Michel

Here the piece of code where is defined the shadermaterial.. this._shaderMaterial = new THREE.ShaderMaterial({ uniforms: currUniforms, vertexShader: vertex, fragmentShader: fragments, side: THREE.FrontSide, depthTest: true, //depthFunc: THREE.GreaterEqualDepth, blending: THREE.AdditiveBlending, //depthFunc: LessEqualDepth, depthWrite: true, //alphaTest: 0.1, transparent: false, // lights: true, / extensions: { fragDepth: true, },/ });