From previz to film: the Episode 10 train fight

The brief

Episode 10 of Champions of Origin pits Chrono Sage, a fighter who bends time, against the Star Devourer, a cosmic being who fights with gravity and two orbs. Midway through the episode the fight needed to move somewhere new. The brief was simple to say and hard to film: the two of them land on an elevated train racing through a neon city, smash down into the carriage, and fight through the train, tearing it apart until the city is roaring past outside.

Two rules shaped everything that followed. Each scene had to be one continuous shot, with the camera following the fighters and circling them rather than cutting away. And the sequence had to be built around the Star Devourer, keeping him at the centre of the frame.

Step 1: block it in Blender

Before anything was generated, the whole fight was built as previz in Blender: simple blocky stand-ins for the characters, a four-carriage train, and a city of boxes and lit windows. That is where the camera moves and timing were decided.

A few tricks kept it manageable. The train never actually moves; the city scrolls past it at about 72 km/h, which keeps the physics simple. The carriage walls, windows, roof panels and seats are built to break apart on cue, and a wind force blows the debris backwards off the train as if it were caught in the slipstream. The Star Devourer's orbs orbit him on a rig that spins up, crawls when Chrono slows time, and snaps back to full speed when he steps out of it.

The first version ran to three scenes of 15, 15 and 30 seconds, and a fourth, with a second train coming the other way, was added later. We then checked framing at more than 70 points through the timeline, so we knew who was in shot, and who deliberately wasn't, at every moment.

Step 2: generate it, one long take at a time

Each scene was then generated as a single 30-second continuous take with a generative video model. The previz set the action, the camera and the pacing; the written direction set everything the blocky previz couldn't show.

Consistency came from reference sheets. Each character has a turnaround sheet that fixes their costume and face, and a line-up sheet fixes their true sizes, so Chrono stays 1.83 metres and the Star Devourer 2.2 metres in every frame. Alongside that, a set of locked rules ran through every prompt: the train is always at extreme speed, the orbs are always two solid, visible spheres, and when Chrono slows time, the bubble holds both fighters while the world outside it keeps racing past.

It took more than one pass. The first takes had too many pauses, with fighters standing and waiting for each other, and the orbs blurred into a single line of light. The direction was rewritten to make the fight relentless and to keep the orbs whole, and the second round worked. Every scene was generated with sound effects only and no music, so the score could be written later.

What the plan didn't predict

Generation is not a photocopier. In the third scene the model ended the take with Chrono clinging to the rear of the train, not the torn floor the previz showed. The take worked, so we kept it, and that set a rule we now use on every sequence: each new scene starts from the last frames of the take we chose, not from the original plan. The previz decides the shape of the fight; the footage decides what happens next.

Step 3: grade it as one film

Generated clips rarely match each other straight out of the model, so the episode was graded in DaVinci Resolve, clip by clip. Each of its 100 clips was measured and matched to its location, so all the train shots share one look: cold night blue with the Star Devourer's violet as the accent colour. A gentle glow and fine 35mm grain across the whole episode tie it together.

Step 4: score it to the cut

The music was written last, to the finished edit. The train fight has its own industrial cue at 150 BPM, built from a train-wheel rhythm, struck-metal percussion and gritty synth bass, so it sounds nothing like the drums of the street fight before it. Every big moment is mapped to the second: the crash through the roof, the orbs spinning up, a tape-stop as Chrono slows time, and the final punch that ends the fight.

The result

About two minutes of continuous, fast fight action across four scenes, from the first landing on the roof to the Star Devourer chasing a second train down the viaduct. You can watch the full episode here.

The same pipeline (plan it in previz, generate it in long controlled takes, then grade and score it by hand) is what we use for brand films, ads and trailers. It's what lets us promise a client the shot they approved, rather than whatever the model happens to produce.