How to show a continuous color scale legend for Scatter3d chart?

[oat]

May I ask how to show a continuous color scale in the following Scatter3d chart in which the color of the points/marker is associated with a variable of float value “df_frame[‘cen_z’]”?

When I added showlegend=True in .update_layout(), only a trace o dot legend is shown…

Code:

fig_frame_cen = go.Figure(
    data=[go.Scatter3d(
        x = df_frames['cen_x'],
        y = df_frames['cen_y'],
        z = df_frames['cen_z'],
        mode='markers',
        marker = dict(
            size=2,
            color=df_frames['cen_z'], 
            colorscale='Viridis',
            opacity=0.8,
        ),
        text='id:' + df_frames['id'],
    )],

) 

fig_frame_cen.update_scenes(
    aspectmode='data',
    aspectratio=dict(x=1, y=1, z=0.001),
    camera=dict(
        eye=dict(x=1, y=-5, z=5)
    )
)

fig_frame_cen.update_layout(
    title=dict(
        text='Positions of Centers',
        x=0.5,
    ),
    showlegend=True,
)

fig_frame_cen.show()

Output: