Tutorial: weather and camera variation

A dataset where every frame looks the same teaches a model very little. This tutorial covers the two biggest sources of useful variation in Studio, where the camera is and what the sky is doing, plus the validation that stops variation from producing garbage.

Camera modes#

The five presets on the Capture page set several fields at once. They are starting points, and every value stays editable afterwards.

Ranges are the point

A single number pins a value. Two comma-separated numbers randomise it per frame.

Distance (m)     8,30
Altitude (m)     6,22
Field of view    55,80
Yaw              0,360

That alone turns one viewpoint into thousands. Start wide, then narrow if your smoke test shows targets that are too small or clipped.

Fixed cameras from the viewport

To reproduce a real installed camera, fly the editor viewport to exactly the pose you want, then press Fixed from Viewport. It creates or updates a CameraActor at that exact position, rotation and field of view, and switches the recipe to Fixed mode.

Smart Viewpoint Validation#

Randomised cameras produce bad frames: nothing in view, a target three pixels wide, the lens inside a wall, a frame so dark it is noise. Viewpoint validation rejects those samples and draws again before they reach your dataset.

Choosing a fallback

Weather#

Pick exactly one driver on the Capture page:

• NameFrame weather (default), built in and works in any project.
• Ultra Dynamic Sky / Weather, which drives the UDS/UDW Blueprint actors if your project has them.

Only the selected driver's controls are shown. Shared output settings stay visible for both.

Built-in weather

The Capture page gives you five preset buttons (Clear, Fog, Rain, Storm, Snow) plus Random, which samples per frame using the weights you supply:

clear_sun:40,fog:20,rain:20,storm:10,snow:10

Weights are relative, so they do not need to sum to 100.

Those buttons are shortcuts, not the whole set. Nine profiles ship in total, including daytime, golden_hour, overcast and night, and you can type any of them into the Weather field or the weights string. Each one with its exact sun, fog and cloud ranges is in Weather, sky and UDS.

Ultra Dynamic Sky

The Sky parameters and Weather parameters fields set UDS/UDW properties directly, as Property=value pairs separated by semicolons:

Time of Day=900,1700;Cloud Coverage=0,10
Weather=clear_skies|rain_light|snow

A comma pair is a numeric range, a pipe list is a set of alternatives, and default leaves the driver untouched.

Rain and snow particles

Composite rain and snow particles into generated output is on by default, and it exists for a specific engine limitation. UDS/UDW precipitation is GPU Niagara, which Unreal does not render inside editor scene captures. Without compositing, a "rainy" frame comes out with wet-looking ground and no visible rain. The option draws the precipitation onto the report and dataset images instead. It works with both weather drivers.

Lens and sensor simulation#

Perfect renders do not look like camera footage. The Lens and sensor section on the Dataset page applies a profile after capture, so you can change it and re-export without re-rendering.

Twenty-seven distinct looks ship, from realistic_drone and dashcam through cctv, bodycam, night_vision, thermal_white_hot, rainy_lens and vhs_analog. The complete list, with what each one looks like and which camera it is meant to imitate, is in Camera lens profiles. Intensity scales the effect, where 1.0 is full strength.

Set the profile to random and supply weights to mix them across the run:

realistic_drone:40,dashcam:25,rainy_lens:20,cctv:15

A variation strategy that works#

1. Get one clean frame first

   Fixed camera, clear weather, no lens profile. Prove the labels are correct with zero variation in play.

2. Add camera variation

   Switch to Orbit or Drone with wide ranges. Smoke-test. Confirm targets are still well framed at both ends of every range.

3. Add weather

   Random weather with weights matching your deployment. Smoke-test again and look at the images, because this is where settle time problems show up.

4. Add lens last

   It is post-capture, so it is the cheapest thing to change and the easiest to over-apply.