1 The idea
An explosion has a fixed order: a short flash with debris launching on detonation, then the fireball builds, then smoke takes over. Light reaches the camera almost at once, but the shockwave travels at about 343 m/s, so the camera shakes later than the flash, by an amount set by the distance.
The fireball here is locked to the detonation frame. Move the flash, debris and camera shake sliders, watch each event’s offset from detonation and the shockwave marker on the timeline, then press ▶ Play to watch the whole shot.
delay = distance ÷ 343 m/s × 24 fps = 73 ÷ 343 × 24 ≈ 5.1 frames2 Hands-on
Task: place the flash, the debris and the shake start so the explosion plays in the order physics gives it.
Compare each event’s offset with detonation, and see where the “shockwave reaches camera” marker sits on the timeline. The distance and the delay are in the readouts; the shake’s own shape is in M6.
3 Deep dive
The order of an explosion
The flash is the shortest event: 1–2 sharp frames, right on detonation. Debris launches with it, not after the fireball has already grown.
The fireball should build in brightness rather than start at its peak, and as it fades, crunch it (gamma down the emission) so the smoke takes over instead of staying bright to the end.
- 1Flash, 1–2 frames
- 2Debris launch
- 3Fireball grows
- 4Smoke takes over
- 5Shake on arrival
Light first, shockwave later
Light is fast enough to count as instant, but the shockwave moves at about the speed of sound, 343 m/s. Delay in frames = distance ÷ 343 × 24 at 24 fps. Here the blast is about 73 m away, so about 5.1 frames, rounded to 5.
This lesson is only about when the shake starts; the shape of the shake itself is in M6.
| Distance to blast | Delay at 24 fps |
|---|---|
| 34.3 m | about 2.4 frames |
| 171.5 m | 12 frames |
| 343 m | 24 frames (1 second) |
| 686 m | 48 frames |
Write the key frames before you start
Before touching a node, write down the key frames: detonation, flash, debris, shockwave arrival and the point where smoke takes over. Then design every event frame by frame against those numbers, and the elements, interactive light and shake line up by themselves.
The flash frame also hides cuts well. If you need to swap elements, use a Switch keyed on that frame, not an animated disable knob.
Put the key frames in a sticky note next to the script, so everyone works to the same numbers.
Making the blast sit in the shot
An explosion lights near and far smoke and casts and reflects light on the ground. Too warm and it reads as a sand explosion. Don’t over-saturate it either: gamma down adds saturation, so counter it.
A very bright explosion can go after the shot-wide glow so its glow is controlled separately. Camera shake sits after the glows, and grain always comes last.
4 In real work
In Nuke
- TimeOffset on the fireball element so detonation lands on the written key frame.
- Exposure + Glow keyed for a 1–2 frame flash on detonation.
- A Switch keyed on the flash frame when you swap elements; never animate disable.
- Merge the elements onto the plate: fire as light (plus), smoke over with its own alpha (FE1, FE2).
- CameraShake: key the amplitude up from 0 so it starts at detonation + delay; don’t key the frequency.
- Transform or overscan so the frame edges stay covered while it shakes.
Common mistakes → the fix
- ✗ Shaking the camera on the flash frame of a distant blast✓ Start the shake at detonation + distance ÷ 343 m/s.
- ✗ A flash that lasts many frames or comes after the fireball✓ A sharp 1–2 frame flash on detonation.
- ✗ Debris launching late, after the fireball is already big✓ Launch the debris with the detonation.
- ✗ Keeping the fireball bright to the end✓ Crunch it as it fades (gamma down the emission) and let the smoke take over.
- ✗ Animating a node’s disable knob to swap elements✓ Use a Switch keyed on the flash frame.
Before you send the shot
- Key frames are written down and every event matches them.
- The flash is 1–2 frames, on detonation.
- Debris launches with the detonation.
- Shake starts on the shockwave’s arrival, with no outlier frames and no exposed edges.
- The fireball fades into smoke, not too warm or too saturated.
- Shake sits after the glows, and grain is last.
5 Check yourself
The blast is about 73 m from camera. When should the camera start to shake?
🔒 Answer the question above and this card opens
1. Which explosion flash is right?
2. You need to swap from one explosion element to another. What’s the best way?
Where the numbers come from: The fireball and smoke are one Mantaflow sim of ours (fuel burst for 3 frames), rendered with the scene’s sun and sky. The blast is small on screen and smooth. Flash, debris and shake are drawn in the browser as a teaching version. 343 m/s is the speed of sound in air at about 20 °C (physics, not measured on the pictures). Every element is our own: Mantaflow sims in Blender 5.2, rendered in Cycles through the plate’s camera (EmberGen could not export headless on this machine). No stock elements.