How can i do mirror effect in keyshot?
If you select "ground reflections" option in "environment" section. Then your model will reflect at ground. However you wont have control over amount of reflection with that way. If you want more mirror like reflection you should use a physical plane for your ground ( i mean 3d model for ground ) Then you can change its reflection value as desired.
Second option is mirroring silouette of model in photoshop. Then you can play with opacity value to find exact result. I thnik this option is more confortable because you can easily get rid of much time from rendering process ( reflections and reflactions extending render time extremely )