Study results on virtual reality (VR) environment properties and their impact on presence have been contradictory. And due to the media specificity of VR, which includes place illusion, rules for environment design cannot directly be transferred from 3D computer games or stereoscopic film to VR. This study develops a model for VR environments based on Mel Slater's observation that place illusion in VR is caused by the use of sensorimotor contingencies (SMC). It defines properties of the environment which provide action possibilities for SMC as sensorimotor affordances (SMA). SMC and SMA form a bidirectional feedback loop of perception. This model helps to clarify former contradictory study results on VR environments, and also provides the basis for a framework of preceptual design rules for VR environments.