Depth comes from shadows where things touch
Realism is mostly about shading where things meet. Where the sofa stands on the floor, the wardrobe meets the wall and the ceiling meets the walls, a soft shadow of about 60 cm appears. The eye reads it as contact, and furniture stops floating.
The rest is like editing a photo. Bright areas by the window don't burn out to white, lamps get a slight glow, the edges of the frame are a little darker. Colours are a touch muted, contrast a touch higher, and jagged edges are smoothed.
You can keep working with Realism on
Turning it on doesn't pause the editor. You move an armchair or change the wallpaper, and the shadows and tone stay. On a weak laptop the effect loads the graphics card noticeably, so turn it off with the same button while arranging and back on before showing. Realism is available from the Designer plan up.
Photo mode computes light for real
Photo mode uses ray tracing. It follows light from the window and lamps through its bounces to the camera. The shot develops pass by pass and gains what normal 3D lacks, such as light bounced off walls and floor, soft shadows from the window and highlights in glass and gloss. A counter shows the percentage; after 300 passes the noise barely changes and the shot is ready. Turn the camera and it starts again from the new angle.
The first time, the engine needs up to a minute and a half to prepare. Download PNG saves the shot without editor panels, ready to send.
One angle at noon, evening and night
The time-of-day bar moves the sun in ten-minute steps, and the button beside it cycles day, evening and night. A run plays the whole 24 hours in half a minute. In the evening the apartment's lamps come on; at night it is dark outside and only artificial light is left. You see whether one kitchen ceiling light is enough and whether the armchair corner stays dark. Set the address in Location on the map, and the sun follows its real path over that building in the chosen month.
Clients see Realism in the tour too
If the effect is part of the tour author's plan, a 3D tour link opens with Realism already on. Viewers get their own button to turn it off on a weak device, with no sign-up. Photo mode stays in the editor, since it is for finished shots and the client is exploring a live scene.