c# - Issues with making a 3D model faces semi-transparent using HelixToolkit -

i trying display 3d model depicted below using helixtoolkit. (the following snapshot's taken solidworks.)

i set brush color of diffusematerial used material , backmaterial of geometrymodel3d tranparent color.

model3dgroup facevisualentity = modelfaces.first(modelface => modelface.content.getname() == facename).content model3dgroup;  // breaking 3d-model down constituting mesh.. // foreach (var child in facevisualentity.children) {     if (child geometrymodel3d)     {         geometrymodel3d body = child geometrymodel3d;         body.material = new diffusematerial(new solidcolorbrush("#40ff0000"));         body.backmaterial = new diffusematerial(new solidcolorbrush("#40ff0000"));     } } 

however, can see in helixviewport3d below.

while sides of box seem transparent, wonder why pipes inside box cannot seen. changed color of pipe walls opaque value, cannot see them yet.

the fact using transparency feature of helixtoolkit not achieved changing alpha channel of model faces material only. actually, there example in helixtoolkit code showing sortingvisual3d required support transparency model. so, first added instance of sortingvisual3d helixviewport3d , added visual3d objects, such modelvisual3d, linesvisual3d, etc., it. result, can see below.