Hi @VineetMenon
When you are creating a SimpleMarkerScene symbol (which can be a cone, tetrahedron, tube etc) you create it by specifying the height, width and height. The difference you are seeing with your geodesic buffer can be explained because you are working with a radius from a point effectively.
I fixed your code by setting the size of the symbol dimensions to twice the radius of your buffer. Note that because you are working in 3D with a SimpleMarkerSceneSymbol, the shape you end up with is a geodetic albeit slightly generalised.
// the size needs to be 2 times the radius of the buffer
SimpleMarkerSceneSymbol redSphereSymbol = new SimpleMarkerSceneSymbol(SimpleMarkerSceneSymbol.Style.SPHERE, 0x77FF0000, radius * 2000,
radius * 2000, radius * 2000, SceneSymbol.AnchorPosition.CENTER);
Graphic rangeBalloon3D = new Graphic(centerPoint, redSphereSymbol);
This is the result with the corrected dimensions:
Does this help?