Mental Ray Shadow Flickering

Ways to suppress/reduce flickering in mental ray render

1. using raytrace shadow + GI + FG

    Light Attribute - increase shadow rays of ray trace shadow

    Render Settings > Final Gathering > Final Gather Tracing :

        Final Gather Mode = Optimize for Animations

        set Max/Min Radius

2. using raytrace shadow + GI + Occlusion

    ?

3. using mental ray shadow map + GI + FG

    Light Attribute > Shadows - check using mental ray shadow map

        set Resolution/Sample/Softness as you like

4. using IBL (Image Based Lighting) without photon emission(?)