How to control appearance of cesium 3D tiles. Specifically, edging and shading.

This image of my output display on a CesiumJS website demonstrates where I am up to.

I am trying to convert GDB multipatch to C3DT.

I can control colour through either geometrycoloursetter or appearancesetter but I cannot figure out how to prevent dark shading on top of models nor create defined edges to accentuate the geometry.

I want the edges to look like this: