WorldViz User Forum - passthrough fragment shader

I am trying to do a bit of vertex (and hopefully geometry) shading with the vertices of a node. Specifying a shader program with no fragment shader, or specifying the below fragment shader however both lead to color of the node being discarded.

Code:

obj = vizshape.addSphere()

shader = viz.addShader(vert=getVertexCode(),frag=None)

obj.apply(shader)

fragment shader instead of None above:

Code:

void main()

{

        gl_FragColor = gl_Color;

}

Could you let me know what the passthrough vertex shader should look like in this case?