transparent ground plane?

[PeterSwift]

If I want to render with transparent background but I also want to control the ground shadow so I add a ground plane. But then the ground plane is not transparent in the rendering.   

How do you fix this so everything is transparent inc the ground plane. I'm trying to figure out material graph but I don't get it working.  Is a product in a cylinder shape.  standing on the ground plane.

[TGS808]

Before you render your image, make sure that "Include Alpha (Transparency)" is checked in your output settings. Also, make sure your ground plane is using the default "ground" material. If you do this, your ground plane will be transparent.

[PeterSwift]

ah my Issue I see now that its becosue I tried to fade out the ground shadow using a occulusion material. It made the ground plane visable in my transparancy. So i tried the using a gradient map material instead and that work just fine

So I found the issue thanks anyways .

[TGS808]

Perhaps I misunderstood your question. Outside of using an opacity map to hide parts of a ground plane, using the "ground" material is the only way to ensure the ground plane will be transparent in your scene and still retain the shadows that fall on it. Any other material applied to the ground plane will result in the ground plane being visible in the scene, which is why you could see it when you applied the occlusion material to it. So, I guess having the ground plane be transparent wasn't quite what you were after. Sounds more like you were trying to control some aspect of the shadow. Either way, good that you found some sort of a solution to your problem.

[PeterSwift]

I wanted it transparent. I just got confused when occlusion material overrode the ground plane material properties even when it was just an opacity map.
But when I change to gradient map to the opacity map, to fade the ground shadow, it worked just fine.

[TGS808]

Yes, as I said, any other material besides "ground" on a ground plane will override the transparency and render the ground plane visible. Gradients in the opacity channel however work great for fading out a ground plane when any material other than ground is applied.