Thanks again for help & advice on how to create the perfect sunrise/sunset.
My next problem is bryce volumetric clouds.
I estimate that it will take upto ten days on my quad PC to render a simple sunset scene, at 1080 resolution, using
Is they a way to reduce the render time and still produce great clouds?
Yes, many ways.
1 - lowering the quality setting of the volumetric material will reduce render time.
2 - reducing the thickness of the slab the material is applied to will reduce tender time.
3 - careful control of lighting.
Be aware shadow intensities of under 100% will impair the rendering of volumetric materials.
Also, any soft shadows on light sources present will severely impact on render times.
If HDRI backdrop is used. Make sure there is 0 output in diffuse or specular channels.
If additional light sources are used, and even if the slab is excluded from their influence, this will still have an impact on render time.
If you can cover up the horizon in some way that blocks off the rendering of that portion of the sky (distant mountains for example), this is highly beneficial to rendering.
Altering the AA render tolerance can help considerably. Default is 15 but this can be raised much higher without a negative effect on the appearance of volumetric clouds. Look in Render Options menu on the right hand side to find AA tolerance control.
Edit, this final option only works for regular rendering mode, and only affects the AA pass, so it will not have any impact on the predicted render time. But it will have an impact in real terms.