How to generate a character on green so it keys cleanly afterwards
Tell Vizard Agent the shot is for compositing and ask it to generate the character onto a plain green field. It then measures whether that green stayed one consistent colour across the whole shot — generated backgrounds drift as the subject moves — and tests the key against the finest edges in the design before committing to a render.
What is the short version?
A character generated standing in a room is part of that room. The edges are lit by it, the shadows belong to it, and no amount of cutting out afterwards gives you a subject you can drop onto something else.
- Tell Vizard Agent the shot is for compositing.
- Ask it to check the green is consistent across the shot.
- Ask it to test the key on the finest edges first.
What do you need before you start?
The character design and a decision about what the shot has to do. Vizard Agent generates differently for a plate than for a finished scene, so the compositing intent has to be stated before the first frame rather than discovered afterwards.
- The character reference. Ideally several angles.
- What the character does. The action, in seconds.
- The shot length. These are usually short.
- What goes behind it. Even roughly.
- The finest detail. Whiskers, hair, feathers, lace.
What do you type into Vizard Agent?
Say plate to Vizard Agent, not shot. The instruction that actually matters is that this is an element rather than a picture, because anything asked for a good-looking shot will light the subject to a background it has just invented for itself.
Prompt
Variants worth knowing:
- "A plate for compositing." Changes how it is generated.
- "Stays one consistent colour." Generated green drifts.
- "Test the key against her hair." Where a key fails first.
What does Vizard Agent actually do?
Here is the Vizard Agent sequence on a real series of four-second character plates, each one built from its own reference sheet. The two measurement steps in the middle of it are what separate a genuinely usable plate from a merely nice-looking shot.
- Opens the character reference sheet and reads the design.
- Generates the opening keyframe of the character on green.
- Checks that keyframe before animating anything.
- Animates the action from that keyframe.
- Reviews the frames and zooms in on the timing of the movement.
- Measures the background green for consistency across the shot.
- Tests the chroma key and inspects the edges it produces.
- Checks the key quality at the hair, whiskers or other fine detail.
- Measures the character's position in the frame.
- Renders the final shot with its camera move and checks it back.
Step six is the check that catches generated plates out. A filmed green screen is lit once and stays put; a generated one is re-invented every frame, so it can drift in hue or brightness as the subject moves and the key that worked on frame one falls apart by frame sixty.
Step eight is where keys actually fail. A solid body silhouette keys easily; whiskers, flyaway hair and feather edges are the parts that either survive or turn into a hard cut-out, and they are worth testing before the expensive render.
Step two matters because the keyframe governs everything after it. Getting the character right as a still — on green, correctly framed — is far cheaper than discovering a problem four seconds into an animated shot.
What does the result look like?
An element rather than a picture. A character on clean green, keying to a usable edge including the fine detail, positioned consistently in frame, and Vizard Agent tells you what the green measured and how the edges held up.
When does this not work well?
Green is a bad choice for some designs. A character wearing green, or one with translucent or reflective parts, will lose pieces of itself to the key, and a different backing colour or a generated matte is the better route.
- Green in the costume. It keys out with the background.
- Translucent or glassy parts. They pick up the backing colour.
- Very fine or motion-blurred detail. The edge is unrecoverable.
- Shadows you wanted. They belong to the plate, not the scene.
- Long shots. The longer it runs, the more the green drifts.
How do you fix a result that came back wrong?
Say whether the problem is the green or the edge. Those are separate failures — one is the background not holding still, the other is the key not coping with the detail — and Vizard Agent measures them separately.
- "The key falls apart halfway." The green's consistency is measured again.
- "Her hair is cut out hard." The key is retested on the fine edges.
- "Part of her costume vanished." A different backing colour is used.
- "She drifts in the frame." Her position is measured and the shot re-rendered.
How does Vizard Agent compare to doing it yourself?
By hand you generate a lovely shot of the character in a scene, then spend the afternoon rotoscoping her out of it, losing the hair in the process. Generating onto green instead takes the same time and gives you something you can actually use twice.
| By hand | Vizard Agent | |
|---|---|---|
| What you generate | A finished shot | A plate for compositing |
| The background | Invented and lit | Plain, and measured |
| Discovering a bad key | After the render | On a test before it |
| Fine edges | Lost to rotoscoping | Tested specifically |
| Reuse | One background only | Any background later |
Common questions
Why not cut the character out afterwards? Because the edges are lit by the scene. Vizard Agent generates onto green instead.
Does generated green really drift? It can, because each frame is re-invented. Vizard Agent measures it.
What if my character is green? Say so and Vizard Agent uses a different backing colour.
Will the hair survive? Vizard Agent tests that specifically before rendering the full shot.
Can it deliver with transparency? Yes. Ask Vizard Agent for a format that carries an alpha channel.
How long can the plate be? Short is safer. Vizard Agent will tell you where the green starts to drift.
Can it do a camera move on green? Yes, and the position is measured so the subject stays where you expect.
What about shadows? They belong to the new background. Ask Vizard Agent to add them there.
Can it do several characters as a set? Yes, and the same recipe is reused so they match.
What if I want the subject framed differently? Vizard Agent measures the position; say where you want it and it re-renders.
Does this cost more than a finished shot? About the same, and the element can be reused.
Can I see the key test? Yes. Ask Vizard Agent for the edge test before it renders.
What about motion blur? Blurred edges key badly. Vizard Agent will flag where that happens.
Is blue ever better? For a green costume, yes. Vizard Agent picks the backing that suits the design.