ANR Tools

ANR Clouds

Volumetric clouds from a roto or any alpha: the shape becomes a lit, puffy 3D cloud with sun, sky light and self-shadowing, rendered in Nuke.

In Nuke: NodesANRSimulationsANR Clouds

Overview

Clouds turns a mask into a 3D cloud. The silhouette is filled with a rounded, noise-carved volume and rendered with a sun that casts shadows inside the cloud, a soft sky fill, ambient occlusion in the dense core, and a silver lining when the sun is behind it. What you roto is what the cloud fills: the noise cuts inward and the edge only feathers a little past the roto line.

Use it for sky replacements and set extensions, a cloud bank behind a building, clouds to fly past, or to dress a matte painting. There is no simulation: every frame is built from the mask on that frame, so scrubbing, retiming and farm renders need no cache.

Cloud builds the shape: thickness, puffiness, coverage and the noise that carves the billows. Evolution and Drift animate the inside of the cloud without moving the mask. Look and Light set the material and the lighting, and Placement orbits, moves and turns the finished cloud; none of these rebuild the shape, so they render straight away.

Inputs

MaskEnvironmentCloudsOutput
  1. Maskrequired

    The cloud's outline: a roto, a key or any alpha. Set Mask from to Luminance for a white-on-black image. Animate it and the cloud changes shape.

  2. Environmentoptional

    Optional linear latitude-longitude HDR image. With Use environment map on, it adds broad ambient colour on top of the sky fill.

Output. Premultiplied, linear RGBA of the cloud over a transparent background, ready to merge over the sky.

Quick start

  1. Roto the cloud shape, or use any alpha, and connect it to Mask.
  2. Add ANR Clouds and view it. The first render loads the GPU engine, with a progress bar.
  3. Set Quality on Look to Preview while you work: a small image without shadows.
  4. Shape it on Cloud: Thickness and Puffiness for the body, Coverage and Noise for holes and billows, Wispiness for torn edges.
  5. Light it on Light: Sun azimuth and Sun elevation set where the sun is, Sky color and Sky fill the ambient light.
  6. Turn or move the cloud on Placement if needed.
  7. Set Quality back to Render and merge the result over the plate.

The panel

The node's panel as Nuke shows it, with the values of a new node. Click any control to see what it does; tabs and sections work as in Nuke.

ANR_Clouds1

Mask channel, detail, and the cloud's shape, structure and animation.

StatusConnect a mask. The GPU engine loads on the first render.
Mask fromAlpha
Detail160
Thickness0.35
Puffiness0.3
Edge softness0.25
Depth position0.5
Coverage0.6
Noise0.6
Noise size0.25
Noise detail5
Roughness0.55
Wispiness0.5
Seed1
Evolution0
Drift X0
Drift Y0
Drift Z0

All controls

Cloud18 controls

Mask channel, detail, and the cloud's shape, structure and animation.

Setup

StatusStatusbackendInfo

What the engine is doing: waiting for a mask, loading, the size of the cloud's volume grid, Preview, or an error.

Mask fromMenumaskChannel

Alpha for roto and keys; Luminance for a white-on-black image.

Default: AlphaOptions: Alpha Luminance

DetailSliderresolution

Cloud voxels along the longest image side, 24 to 512. Shape resolution only; output pixels are independent. 160 is a good start.

Default: 160

Shape

ThicknessSliderthickness

Cloud depth as a fraction of the longest image side. 0.35 is a plump cumulus slab; 0.1 is a thin sheet.

Default: 0.35

PuffinessSliderpuffiness

How far in from the silhouette the cloud keeps rounding. Larger makes bulging dome-like lobes; smaller keeps a flatter slab with rounded rims.

Default: 0.3

Edge softnessSlidersoftness

Feather outside the mask edge, relative to Puffiness. Softens the silhouette so the cloud does not cut off on the roto line.

Default: 0.25

Depth positionSliderdepthPosition

Where the cloud sits through depth: 0 back, 1 front.

Default: 0.5

Structure

CoverageSlidercoverage

How much of the shape survives the noise. 1 keeps everything solid; lower values open holes and break the cloud into cells.

Default: 0.6

NoiseSlidernoiseAmount

Strength of the 3D noise that scallops the silhouette and carves the billows. 0.5 is a round full cumulus, 1.2 is stormy and torn.

Default: 0.6

Noise sizeSlidernoiseSize

Largest noise wavelength as a fraction of the longest image side.

Default: 0.25

Noise detailSlidernoiseDetail

Number of noise layers, each half the size of the previous one.

Default: 5

RoughnessSlidernoiseRoughness

How much each finer noise layer contributes. Higher is crunchier.

Default: 0.55

WispinessSliderwispiness

Extra fine erosion at the rim for feathery, torn edges.

Default: 0.5

SeedSliderseed

Different noise pattern per seed.

Default: 1

Animation

EvolutionSliderevolution

Noise phase. Animate this for a cloud that slowly boils in place without moving.

Default: 0

Drift XSliderdriftX

Noise travel per frame in fractions of the longest side. Animates the internal structure sideways.

Default: 0

Drift YSliderdriftY

Noise travel per frame, up.

Default: 0

Drift ZSliderdriftZ

Noise travel per frame, toward the camera.

Default: 0

Look7 controls

Cloud colour, density, absorption, Preview or Render quality, and render-time detail.

Material

Cloud colorColourcloudColor

Cloud albedo. White for daylight cumulus; tint for dusk or storm clouds.

Default: 1

DensitySliderdensity

Overall cloud density. Higher is thicker and whiter; lower is more translucent.

Default: 1

AbsorptionSliderabsorption

Light absorption along the path through the cloud. Lower lets light through the cloud body.

Default: 5

QualityMenurenderQuality

Preview renders a 320 pixel image without shadows for fast interaction. Render is full quality.

Default: RenderOptions: Preview Render

Render detail

Render detail modeMenudetailMode

Finer ray sampling with procedural detail. 4x costs more render time.

Default: 2x samplingOptions: Off 2x sampling 4x sampling

Render detailSliderdetailAmount

Procedural 3D detail added while rendering, on top of the authored volume. No effect on the shape resolution.

Default: 3

Detail sizeSliderdetailSize

Wavelength of the render detail in voxels.

Default: 4

Sampling3 controls

Volume filter, smoothing and ray step: finer is slower.

Volume filterMenuvolumeFilter

Smooth cubic softens voxel facets; Linear keeps more authored detail.

Default: Smooth cubicOptions: Linear Smooth cubic

SmoothingSliderfilterWidth

Extra volume smoothing in voxels. 0 keeps the chosen reconstruction filter.

Default: 0

Ray stepSliderrayStep

Distance between ray samples in voxels. Lower is finer and slower.

Default: 0.75

Light9 controls

The sun and its self-shadowing, the sky fill, and scattering through the cloud.

Sun

SunSlidersunIntensity

Directional key light with self shadowing inside the cloud.

Default: 2.2

Sun azimuthSlidersunAzimuth

Horizontal direction the sun comes from, in degrees. 0 is from the camera, 90 from the right, 180 from behind the cloud.

Default: -40

Sun elevationSlidersunElevation

Height of the sun above the horizon, in degrees. Negative lights from below.

Default: 35

Sky

Sky colorColourskyColor

Color of the soft fill light.

Default: 0.5500000119 0.6999999881 1

Sky fillSliderskyIntensity

Soft ambient light in Sky color reaching the whole cloud.

Default: 0.8

Ambient occlusionSliderambientOcclusion

Darkening of the dense core under sky light.

Default: 0.6

Scattering

Light penetrationSliderscattering

How deep sun light bleeds into the cloud body. Higher looks softer and more translucent.

Default: 0.7

Silver liningSlideranisotropy

Forward scattering. Positive brightens the rim when the sun is behind the cloud.

Default: 0.3

Shadow samplesSlidershadowSteps

Samples through the cloud toward the sun.

Default: 32

Environment map3 controls

Optional ambient colour from the Environment input.

Use environment mapCheckboxuseEnvironment

Add broad ambient color from a linear lat-long HDR on the Environment input, on top of the Sky fill.

Default: off

Environment intensitySliderenvironmentIntensity

Brightness of the optional lat-long environment map.

Default: 1

Environment exposureSliderenvironmentExposure

Environment exposure in stops.

Default: 0

Placement11 controls

Projection, orbit, zoom, position, scale and rotation of the finished cloud.

View

ProjectionMenucameraProjection

Perspective or orthographic view of the volume.

Default: PerspectiveOptions: Orthographic Perspective

Orbit YSliderviewYaw

Rotate the view around the cloud, in degrees.

Default: 0

Orbit XSliderviewPitch

Tilt the view, in degrees.

Default: 0

ZoomSliderviewZoom

Camera zoom.

Default: 1

Transform

Position XSlidervolumeX

Move the cloud in world X. 1 equals the longest frame dimension.

Default: 0

Position YSlidervolumeY

Move the cloud in world Y.

Default: 0

Position ZSlidervolumeZ

Move the cloud in depth. Positive is toward the camera.

Default: 0

ScaleSlidervolumeScale

Uniform scale about the cloud center.

Default: 1

Rotate XSlidervolumeRotateX

Rotation about the X axis, degrees.

Default: 0

Rotate YSlidervolumeRotateY

Rotation about the Y axis, degrees.

Default: 0

Rotate ZSlidervolumeRotateZ

Rotation about the Z axis, degrees.

Default: 0

Engine3 controls

Status, GPU scheduling, and releasing the GPU engine.

GPU

StatusStatusbackendInfo_engine

The same status line as on the Cloud tab.

GPU schedulingMenugpuScheduling

Responsive leaves GPU time for the desktop. Maximum speed removes deliberate pauses.

Default: ResponsiveOptions: Responsive Maximum speed

Release GPUButtonreleaseEngine

Free the GPU engine and its memory. It reloads automatically on the next render.

Tips

  • For a storm cloud, raise Noise towards 1.2, lower Coverage and darken Cloud color.
  • Put the sun behind the cloud (Sun azimuth near 180) and raise Silver lining for a bright rim.
  • Animate Evolution for a cloud that slowly boils in place; Drift X, Drift Y and Drift Z move its inner structure while the outline stays.
  • Thickness around 0.1 gives a thin sheet; the default 0.35 is a plump cumulus.
  • Raise Edge softness if the cloud looks cut off along the roto line.
  • Detail sets the shape resolution only, not the output size; 160 is a good start.
  • Render detail with Render detail mode adds fine detail while rendering without rebuilding the shape; 4x sampling costs more render time.
  • When you are done with a cloud, click Release GPU on Engine to free the graphics card's memory; the engine reloads by itself on the next render.

Good to know

  • The cloud renders on the graphics card. The engine loads on the first render and stays loaded until you click Release GPU or a render is cancelled; it then reloads on the next render.
  • At most two Clouds nodes can hold a GPU engine at the same time. If a third reports an error, click Release GPU on one you are not using.
  • The sun's light is white: tint the cloud with Cloud color, or the ambient light with Sky color.
  • Sky fill is one colour from all around, not a gradient from sky to ground.
  • There is no camera input: place and turn the cloud with Placement.
  • Preview has no shadows; check the final look with Quality on Render.

Something unclear or missing? Write to [email protected].