The constraint that changes everything
In film you control the whole frame. In mixed reality you control an object and nothing around it — the wall behind it, the light falling on it, the clutter beside it and the colour of the sofa all belong to somebody's living room.
So the design question stops being "what does this look like" and becomes "what still reads when the background is unknown". Silhouette, contrast against an arbitrary surface, and behaviour at a scale you did not choose.
This is closer to product design or signage than to film. The thing has to work in conditions you will never see, which means designing for the worst case rather than photographing the best one.
Designing for it
Test against the worst room
Generate the same subject against a range of backgrounds — bright, cluttered, dim, warm, patterned — and keep only the designs that still read in all of them. A graph makes this one reference and six branches rather than six separate attempts.
Silhouette first
If it does not work as a shape at thumbnail size, it will not work sitting on a bookshelf across a room. Test the silhouette before the detail.
Light is borrowed
The room supplies the light and it will be wrong. Design something that survives being lit from the wrong side rather than something that depends on your key.
Scale is not yours
It may appear on a desk or across a room. Anything that depends on being a specific size will fail in one of those places.
A test worth running
One subject node
The thing you are designing, as a reference everything else draws from.
Six room branches
Bright white, dark wood, cluttered shelf, warm evening, cool daylight, patterned wallpaper. Deliberately unglamorous.
Look at all six at once
Not one at a time. The failure is visible in comparison and invisible in isolation, which is why designers who test sequentially keep shipping things that vanish in someone's kitchen.
Change the subject, not the rooms
The rooms are the fixed test. Iterate the design against them until it survives all six.
Concept, not runtime
There is also no occlusion, no plane detection and no real understanding of a room — the "rooms" here are generated backgrounds you are testing against, not simulations of a space. That is enough to catch a design that fails on contrast, and not enough to catch one that fails on placement.
Questions
Can I use a photo of a real customer environment?
Yes, and you should where you have one. A generated room is a reasonable proxy; a photograph of the actual space is better evidence.
Does this help with UI design for headsets?
Yes — contrast against unknown backgrounds is the central problem there too, and it is the same test.
What about passthrough colour shifts?
Not simulated. Headset passthrough alters colour and contrast in ways worth testing on the device itself, and no generated preview substitutes for that.