PhysicalCamera class final

An aperture, a shutter time and a sensitivity, and the exposure they make.

The default camera draws the frame this engine always drew. f/4 at a sixtieth of a second and ISO 100 is the reference camera: its exposure value, log2(4² × 60) ≈ 9.907, is the one RenderSettings.exposure is stated at. A camera one stop slower — f/4 at a thirtieth — exposes twice as much, and so on, so exposureScale is 2^(referenceEv100 − ev100) and nothing else: exactly one for the reference camera, which is why the goldens did not move when the physical camera became the default.

What the numbers mean in light. The renderer exposes with the saturation-based model (ISO 12232): the brightest luminance a camera records is 1.2 × 2^EV100 candela per square metre, and the exposure multiplier is its inverse. Holding the reference camera to the default multiplier of 1.6 fixes the engine's photometric scale: one unit of scene luminance is 1.6 × 1.2 × 960 = 1.0 * RenderMaterial.defaultEmissiveStrength cd/m² (RenderMaterial.defaultEmissiveStrength) — and, since a white Lambertian surface shows E/π of an illuminance E, one unit of illuminance is π times that, about 5790.6 lux (LightNode.legacyUnit). Those are the renderer's own business since 1.0: everything the API takes is in lux, candela or nits, and the renderer converts. The physical sky's default sun is about 116 000 lux before the air, which is the real sun's order.

A light meter, not just a dial. ev100ForIlluminance is an incident meter's reading (calibration constant 250): EV100 = log2(E / 2.5). Fed PhysicalSky.illuminanceLux, it says what a camera standing in that light would be set to, and PhysicalCamera.metered makes that camera, solving for the shutter at a chosen aperture.

Auto exposure still decides the exposure while it is on: the meter's answer replaces the camera's, as a camera on automatic chooses its own shutter, and FrameResult.ev100 reports what it chose in these units.

Constructors

PhysicalCamera({double aperture = referenceAperture, double shutter = referenceShutter, double iso = referenceIso, double compensation = 0.0})

A camera at the reference aperture, shutter and sensitivity, with no compensation.

const

PhysicalCamera.atEv100(double ev100, {double aperture = referenceAperture, double iso = referenceIso})

A camera set to ev100 at aperture and iso: the shutter is what makes the three agree.

factory

PhysicalCamera.forSky(PhysicalSky sky, Vector3 toSun, {double aperture = referenceAperture, double iso = referenceIso})

A camera set for the light under sky with the sun along toSun: PhysicalSky.illuminanceLux, metered.

factory

PhysicalCamera.metered(double lux, {double aperture = referenceAperture, double iso = referenceIso})

A camera set as an incident meter reads lux: ev100ForIlluminance, then PhysicalCamera.atEv100.

factory

Properties

aperture → double

The f-number: the focal length over the opening's diameter. Larger is a smaller opening, less light and, where depth of field is on, more of the picture sharp. A unitless ratio.

final

compensation → double

Stops added on top of what the three settings make; positive is brighter, as the dial on a camera. In stops (EV).

final

ev100 → double

The exposure value at ISO 100: log2(N² / t) − log2(S / 100), less compensation. In stops (EV).

no setter

exposure → double

The linear exposure multiplier this camera makes, in the engine's photometric scale: 1.0 * RenderMaterial.defaultEmissiveStrength / (1.2 × 2^EV100), which is referenceExposure × exposureScale.

no setter

exposureScale → double

What this camera multiplies a frame's light by, against the reference camera: 2^(referenceEv100 − ev100). Exactly one at the reference.

no setter

hashCode → int

The hash code for this object.

no setter, override

iso → double

The sensor's sensitivity, ISO arithmetic. Unitless.

final

label → String

f/4 · 1/60 s · ISO 100, as a camera's display would put it.

no setter

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

shutter → double

How long the shutter is open, in seconds.

final

Methods

copyWith({double? aperture, double? shutter, double? iso, double? compensation}) → PhysicalCamera

Returns a copy with the given fields replaced; null leaves a field as it is.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

stopAperture(int thirds) → PhysicalCamera

This camera with aperture moved by thirds thirds of a stop; positive closes it. A third of a stop is a factor of 2^(1/6) in f-number.

stopIso(int thirds) → PhysicalCamera

This camera with iso moved by thirds thirds of a stop; positive is more sensitive.

stopShutter(int thirds) → PhysicalCamera

This camera with shutter moved by thirds thirds of a stop; positive is longer.

toString() → String

A string representation of this object.

override

Operators

operator ==(Object other) → bool

The equality operator.

override

Static Properties

referenceEv100 → double

The reference camera's exposure value, log2(4² × 60), about 9.907.

no setter

Static Methods

ev100ForExposure(double exposure) → double

The exposure value a linear exposure multiplier stands for — what a metered or pinned multiplier would be on a dial.

ev100ForIlluminance(double lux) → double

An incident meter's reading under lux, at ISO 100: log2(E / 2.5), the calibration constant 250 over a hundred.

shutterFor(double ev100, {double aperture = referenceAperture, double iso = referenceIso}) → double

The shutter time that makes ev100 at aperture and iso.

Constants

referenceAperture → const double

f/4, the reference camera's aperture. A unitless ratio.

referenceExposure → const double

The exposure multiplier the reference camera is held to — what RenderSettings.defaultExposure is.

referenceIso → const double

ISO 100, the reference camera's sensitivity. Unitless.

referenceShutter → const double

A sixtieth of a second, the reference camera's shutter.