My new Poser 11 now works. This render used Firefly; the ground plane is set visible, and in its materials "Shadow Catch only" is set on, and as seen here, the ground plane appears in the preview, but not in the render, and the shadows on the ground plane appear on the grass as if the scene was photographed in one shot as seen here. OK, same as Poser 10.

But in Poser 11 in Superfly mode, the ground plane showed in full on the render.

There is no shadow catch only capability in Cycles and Superfly doesn't add much that isn't in Cycles.

I have some tentative tactics for SuperFly but it involves some crazy UV mapping of a custom ground plane I made and precise positioning of the camera.

Not easy. I have not decided to release it as it is difficult to remember to follow the rules and basically I don't feel like supporting it.

I found in the Poser 11 manual file:-

Unsupported in SuperFly: • Ambient occlusion on lights • Smooth Polygons • Custom output 1, 2 and 3 • Specular and Diffuse light shaders • Background node Diffuse_Color, Specular_ Color, and Bump input • Depth Cue • Atmosphere Strength parameter on lights • Quality and ray bias parameters on ray traced nodes • “Opaque in Shadow” checkbox on Hair node • Shadow catchers • Toon outlines

But in Superfly (or in Firefly), how can I get the result in outdoor scenes, of edges of shadows being a bit blurred because the sun is a finite size (half a degree of angle, as seen from Earth) and not a point light source?

bagginsbill posted at 5:19PM Thu, 03 March 2016 - #4259117

There is no shadow catch only capability in Cycles and Superfly doesn't add much that isn't in Cycles.

https://developer.blender.org/D1788

It's a very experimental feature.

This is a Poser11 Superfly render of my previous scene, with default settings. How can I stop the sandy effect in the shadows, e.g. on the underside of the sub, but also somewhat on the men?

Increasing the pixel samples.

Anthony Appleyard posted at 11:50PM Thu, 03 March 2016 - #4259124

But in Superfly (or in Firefly), how can I get the result in outdoor scenes, of edges of shadows being a bit blurred because the sun is a finite size (half a degree of angle, as seen from Earth) and not a point light source?

Use a little Shadow Blur Radius on the infinite light source. I'm not sure about this, but I think the value is supposed to represent the angular diameter of the light source.

Regarding the "sandy effect" - as kalrua says. The grainy effect is normal render 'noise' due to the randomised sampling giving varying results. As you increase the number of samples, these variances are averaged out until eventually there is no visible noise. Usually there will be some surfaces in a scene that are more noisy than others.