THE MATTE · THE SKY · THE LIGHT
Sky Replacement.
Replace the sky.
Keep the world believable.
Sky Replacement cannot find the sky on its own. Start with a sky key, then choose an artificial generator or a real external sky clip. Finally match movement, optics, grain and foreground light.
Qualifier · Window · Magic Mask
Artificial · External RGB
Motion · Grain · Foreground
Lab challenge: disable “Sky key connected”. The effect stops, even if artificial clouds and the hotspot remain configured. That is the key distinction between sky selection and sky generation.
01 / KEY & MATTE
No sky key = no replacement; edge sliders cannot create a missing selection.
02 / ARTIFICIAL SKY
03 / SKY POSITION & FINISH
Changing motion only changes authored offsets. It never performs real image tracking.
Educational mathematical compositor. Original illustrated scene, procedural cloud approximation and pre-authored motion; not the Resolve FX render, automatic keyer or tracker.
Eight genuine DaVinci Resolve PNGs; independent illustrated laboratory.
63 controls & actions · 8 PNG01THREE PARTS OF ONE SHOT
A sky replacement begins before the FX.
The sky-selection key, replacement RGB and final scene integration are distinct signals and distinct decisions.
Select the real sky
A Qualifier, Window or Magic Mask creates the white-sky key. Sky Mask Adjustments refines it but never generates it.
Choose the replacement
Artificial Sky is generated inside the OFX. A real sky clip arrives through a separately added, lower green RGB input. Source Sky Appearance only grades that external clip.
Match the picture
Track movement, avoid exposed edges, then match exposure, lens softness and noise. The foreground must agree with the new sky lighting.
The top laboratory is not a sky detector or a live OFX. It uses an original illustrated scene, a mathematically defined matte and author-created sky textures. All screenshots below are genuine captures of the Resolve interface.
02THE ACTUAL INSPECTOR
Eight groups. Every documented decision.
The source archive contains eight authentic interface PNGs. Some filenames are misleading and some sections are collapsed; control descriptions are checked against the Resolve 21 manual. Values in screenshots are not universal presets.
01 / MASK
Sky Mask Adjustments — matte refinement
Key the sky first using a Qualifier, Power Window or Magic Mask. This group only refines the existing key.
- Preview Mask
Diagnostic black-and-white view of the existing key; white identifies the replacement area. It cannot generate the key.
VerifyTurn on the preview and inspect the horizon and trees.
- Shift Edge
Moves the keyed boundary inward or outward to reduce remnants of the source sky.
VerifyZoom in on small branches and look for bright fringes.
- Refine
Tightens the matte boundary around image detail without replacing the original key.
VerifyInspect trees against the sky over several frames.
- Black Level
Adjusts the matte black point, suppressing weak unwanted transparency.
VerifyCheck that stray plate highlights do not leak into the foreground.
- White Level
Controls the white point and opacity of the selected matte area.
VerifyEnsure broad clear-sky areas remain solid rather than patchy.
02 / SOURCE
Source Sky Appearance — external plate only
These settings do not affect Artificial Sky. They grade RGB from the extra OFX input.
- Color Space
Selects color space of the incoming sky plate; the dropdown includes Use timeline and camera gamuts.
VerifyCompare the plate under a correct versus mismatched gamut.
- Gamma
Selects transfer curve for the incoming sky clip, dependent on the grade pipeline.
VerifyDo not try to fix a wrong Gamma through saturation alone.
- Detail
Changes incoming-plate midtone detail to emphasize or soften clouds.
VerifyInspect fine clouds and noise at 100%.
- Brightness
Adjusts the brightness of the external sky relative to the foreground.
VerifyAvoid an abrupt exposure mismatch at the horizon.
- Saturation
Controls saturation of the incoming replacement-sky plate.
VerifyCompare the cloud saturation against scene reflections.
- Temperature
Warms or cools the external sky plate.
VerifyMatch the visible daylight or sunset direction.
- Tint
Adjusts green–magenta tint in the incoming sky.
VerifyWatch neutral clouds for unwanted casts.
- Opacity
Blends the plate with the original sky at partial opacity.
VerifyAt intermediate settings the original and replacement skies should both contribute.
03 / ARTIFICIAL
Artificial Sky — base sky and horizon
Enable the synthetic generator separately; at zero opacity its components can remain invisible.
- Preview Artificial Sky
Shows the synthetic sky layer without the foreground composite.
VerifyDo not confuse the preview with the final composite.
- Artificial Sky
Enables the synthetic-sky generation controls.
VerifyRaise Sky Opacity after enabling if the result remains invisible.
- Sky Opacity
Opacity of the synthetic sky component; zero removes its contribution.
VerifyCompare zero, partial and fully opaque settings.
- Sky Color
Base color for the artificial sky.
VerifyFor a blue sky, check its coherence with object shadows.
- Horizon Color
Haze color near the horizon.
VerifyAn excessive orange band can look painted on.
- Horizon Softness
Feathering between the main sky and horizon haze.
VerifyAvoid an unnaturally hard horizon stripe.
- Horizon Height
Vertical placement of the synthetic horizon.
VerifyAlign it with the shot’s actual horizon.
- Horizon Angle
Tilts the synthetic horizon/haze.
VerifyUse for a tilted camera without accidental slant.
04 / CLOUDS
Artificial Clouds — cloud structure
Clouds form an independent procedural layer; Time evolves its pattern rather than tracking the camera.
- Artificial Clouds
Enables procedural clouds over the base synthetic sky.
VerifyDisabling this should leave the base sky and any other enabled layers.
- Cloud Opacity
Opacity of clouds relative to the sky.
VerifyCompare diffuse haze with dense clouds.
- Cloud Color
Color of the cloud pattern.
VerifyKeep cloud color consistent with the scene lighting.
- Cloud Scale
Scale of the procedural cloud pattern.
VerifyCompare broad forms with fine noisy structure.
- Cloud Shape
Changes clouds from puffier to elongated shapes.
VerifyEnsure elongated bands have a plausible orientation.
- Cloud Tilt
Rotation of the cloud pattern relative to the ground.
VerifyCompare the cloud angle with scene perspective.
- Cloud Detail
Balance of coarse and fine details within cloud noise.
VerifyExcess detail can make clouds look obviously procedural.
- Cloud Fill
How much of the sky is covered by clouds.
VerifyAvoid obscuring all light around the horizon.
- Cloud Contrast
Contrast between light and dark portions of the cloud pattern.
VerifyMatch cloud contrast to the shot’s dynamic range.
- Cloud Time
Changes the noise phase; keyframing can evolve cloud shapes over time.
VerifyChange Time without mistaking it for Match Motion tracking.
05 / SUN
Artificial Sun — directional hotspot
The hotspot stands in for sun or moon; match it to real foreground illumination.
- Artificial Sun
Enables the synthetic hotspot component.
VerifyMake sure you are not adding a second sun against the shadows.
- Hotspot Brightness
Hotspot intensity; zero removes it.
VerifyBalance the bright area against overall sky brightness.
- Hotspot Color
Color of the synthetic light source.
VerifyMatch a warm hotspot to horizon hues.
- Hotspot Position X
Horizontal hotspot position.
VerifyCheck direction against ground shadows.
- Hotspot Position Y
Vertical hotspot position.
VerifyAvoid placing it below the real horizon accidentally.
- Hotspot Size
Area/size of the light hotspot.
VerifyAn extremely small hotspot may appear as an artificial dot.
- Hotspot Sharpness
Edge sharpness of the hotspot.
VerifyIn hazy shots use a softer transition.
06 / POSITION
Sky Position — matching motion
Actual tracking requires motion footage. The lab uses authored demo motion, not video analysis.
- Match Motion
Options: Keyframing Only, Track Foreground, Track Original Sky and Use FX Tracker.
VerifyChoose a mode based on usable detail in sky or foreground.
- Track Foreground
Runs motion analysis on foreground details in the relevant mode.
VerifyPrefer stable features over moving people or leaves.
- Clear Tracking Data
Clears stored tracking data before a fresh pass.
VerifyRecheck the whole sky path after clearing data.
- Adjust Size
Scales the sky to cover camera movement without exposing empty borders.
VerifyScrub the start, middle and end of the motion.
- Adjust Position X
Manual horizontal adjustment of sky position.
VerifyInspect cloud alignment against the foreground.
- Adjust Position Y
Manual vertical adjustment of sky position.
VerifyDistinguish plate motion from artificial horizon height.
- Auto-Size for Motion
Sizes the replacement according to the recorded motion extents.
VerifyThis needs usable tracking data first.
- Flip Horizontal
Flips the sky image horizontally, moving clouds and light position.
VerifyAvoid flipping if that contradicts the lighting direction.
07 / INTEGRATION
Sky Integration — optics and texture
Matching exposure, lens geometry and grain often determines whether the composite looks convincing.
- Preview Final Sky
Previews the completed sky layer, including motion and keyframed changes.
VerifyUnlike Preview Mask, this is not the grayscale matte.
- Lens Distortion
Warps the replacement sky to match source-camera curvature.
VerifyCompare near the edges of wide-angle footage.
- Lens Defocus
Matches sky defocus to source depth-of-field.
VerifyAvoid overly crisp clouds against a defocused plate.
- Exposure
Adjusts overall brightness of the final sky layer.
VerifyInspect cloud clipping and foreground balance.
- Add Grain
Enables simulated grain on the replacement sky.
VerifyEvaluate at 100% scale across several frames.
- Grain
Amount of sky grain.
VerifyMatch grain density to adjoining image areas.
- Size (grain)
Size of the grain pattern.
VerifyAvoid oversized grain in fine digital footage.
- Softness (grain)
Sharpness or softness of individual grain particles.
VerifyCompare grain texture with source sharpness.
- Saturation (grain)
Chroma in the grain; zero makes it monochromatic.
VerifyOverly chromatic grain stands out against blue skies.
08 / FOREGROUND
Foreground Appearance — scene integration
These controls adapt the foreground to the new sky, not repair a bad matte.
- Adjust Foreground
Enables foreground adaptation to the replacement sky.
VerifyCheck skin and neutrals for unwanted casts.
- Auto Adaptation
None for manual-only; Globally Applied for a global cast; Match Horizon for spatially weighted matching.
VerifyCompare the modes on an unevenly lit foreground.
- Adaptation Amount
Strength of automatic foreground adaptation.
VerifyReduce if skin acquires an unwanted tint.
- Localization
With Match Horizon, adjusts the reach of the horizon-weighted color cast.
VerifyCheck close and distant objects separately.
- Brightness (foreground)
Manual foreground brightness adjustment.
VerifyAlign light direction and shadow contrast.
- Saturation (foreground)
Manual foreground saturation adjustment.
VerifyA dramatic sky should not make the grass unnaturally neon.
- Temperature (foreground)
Manual warm–cool foreground adjustment.
VerifyFor sunsets check the warmth of lit surfaces.
- Tint (foreground)
Green–magenta correction for foreground regions.
VerifyAvoid odd casts on white objects.
03ARTIFICIAL ≠ EXTERNAL
Choose the source before editing its controls.
The most common mistake: attempting to change generated sky with external-plate Color Space, Gamma or Saturation.
| Property | Artificial Sky | External sky plate |
|---|---|---|
| Content source | OFX generator | Media Pool → External Matte |
| Color and gamma | Sky Color · Horizon Color · Clouds | Source Sky Appearance · Color Space · Gamma |
| Opacity | Sky Opacity | Source Sky Appearance → Opacity |
| Additional RGB input | Not required | Required · Add OFX Input |
| Sky matte | Required | Required |
Artificial Sky content uses its own Sky, Clouds and Hotspot controls. Source Sky Appearance settings only work with a footage-based incoming sky.
04ACTUAL COLOR CONNECTIONS
Green carries the picture. Blue carries the key.
Switch between the two source configurations. The diagrams explain the signal path, not a claimed recreation of the Resolve Node Editor.
One node can host the key and generated sky.
Use a Qualifier, Window or Magic Mask on the same Color node as Sky Replacement, or route an upstream key through its blue alpha input. Then set Sky Opacity above zero.
Schematic connection logic, not a screenshot or editable Resolve graph. The blue connection represents the sky selection; the green extra OFX input carries the sky plate RGB.
Also see Color nodes ↗ · Qualifier / Power Window ↗
05CLOUD TIME IS NOT TRACKING
Animate texture and track the camera separately.
Cloud Time
PATTERN ≠ CAMERAChanges procedural cloud noise over time, producing evolving shapes. Does not lock the plate to camera motion.
Keyframe it only if you want clouds themselves to evolve.
Match Motion
4 MODESKeyframing Only, Track Foreground, Track Original Sky, Use FX Tracker. Choose according to source detail and intended camera motion.
Compare the complete shot, not one still.
Auto-Size for Motion
COVER FRAMEAfter usable tracking, sizes the sky to cover tracked motion and avoid uncovered edges.
Inspect first and last frames with wide camera movement.
06BUILD IT IN RESOLVE
Four exercises with a real acceptance check.
Use actual footage; an interactive browser preview does not validate the closed-source tracker or OFX performance.
Synthetic sunset
Replace a dull sky while preserving trees and coherent lighting.
- 01
Key the sky using a Qualifier/Window and inspect Preview Mask around trees.
- 02
Enable Artificial Sky and Sky Opacity; tune Horizon Color, Softness and hotspot position.
- 03
Match the foreground lighting and inspect multiple frames.
Tree edges survive while shadows agree with the new sky.
External storm plate
Wire an external RGB sky plate independently of the generator.
- 01
Create the sky key, apply Sky Replacement and select Add OFX Input.
- 02
Drag the sky clip into the node tree as an External Matte, optionally grading it through a serial node.
- 03
Connect the green RGB output to the Sky Replacement node’s second green input.
- 04
Set Color Space/Gamma, opacity and Match Motion; inspect edges.
The external clip appears only through the keyed sky and tracks coherently.
Replacement during a camera pan
Separate cloud animation from motion matching of the entire plate.
- 01
Choose a panning shot with usable tracking detail.
- 02
Try Track Original Sky and Track Foreground; compare stability.
- 03
Use Adjust Size and Auto-Size for Motion after successful tracking.
- 04
Inspect 10–20 consecutive frames including the image boundaries.
No horizon slip or uncovered edges during motion.
Match grain and exposure
Prevent the replacement from looking unnaturally clean.
- 01
Inspect Preview Final Sky and match foreground exposure.
- 02
Match Lens Defocus/Lens Distortion then add subtle grain.
- 03
Compare sky and foliage at 100% and review rendered frames.
Sky and source share a coherent texture with no obvious seam.
07REPAIR BY CAUSE
When a sky composite fails, inspect the signal first.
01Sky Replacement changes nothing+
Why: There is no sky key, the mask is black, or generator opacity is zero.
What to do: Check Qualifier/Window/Key, Preview Mask and Artificial Sky opacity. For a plate, verify the extra RGB input.
02Source Sky controls do not affect Artificial Sky+
Why: These settings are for the external sky plate only.
What to do: Use Artificial Sky, Horizon, Clouds and Hotspot for synthetic content.
03Branches have halos or disappear+
Why: The original key is imprecise or Shift Edge/Refine is excessive.
What to do: Repair the key, then adjust edge shift and matte levels while playing.
04The external sky plate is missing+
Why: Add OFX Input has not been created or RGB is routed incorrectly.
What to do: External Matte → optional grade node → extra green RGB input of the FX node.
05Replacement sky drifts against the horizon+
Why: Wrong motion method or insufficient usable tracking features.
What to do: Compare Original Sky / Foreground; try manual keyframes or FX Tracker; review sky size.
06Foreground feels disconnected+
Why: Light direction, grain and color temperature disagree with the foreground.
What to do: Balance the hotspot, Exposure, grain and modest Foreground Appearance.
08BEFORE DELIVERY
Check continuity, not one lucky frame.
09FAQ
Common Sky Replacement questions
Does Sky Replacement automatically detect the sky?
No. First build a sky key using a Qualifier, Power Window, Magic Mask or similar tool. Apply FX on that node or route alpha from an upstream node.
Artificial Sky or an external plate?
Artificial Sky is suitable for procedural colors, clouds and hotspot; an external plate uses Add OFX Input and lets you use a specific filmed sky.
Why does Source Sky Appearance not change the generator?
The manual assigns this group to an incoming external sky plate only. Synthetic content is controlled in Artificial Sky.
How do I connect an external sky clip?
On the FX node choose Add OFX Input, then Media Pool → External Matte → optional grade node → extra green FX RGB input. The original sky key is separate.
Preview Mask versus Preview Final Sky?
The first displays the black-and-white selection; the second isolates the final replacement sky with motion and integration.
Can Cloud Time replace Match Motion?
No. Cloud Time evolves procedural noise. Match Motion aligns the replacement to the camera movement.
Why does the foreground color look wrong?
Sky Integration affects the sky; Foreground Appearance adapts the original scene. Use automatic matching gently and watch skin and neutrals.
Is the interactive lab an exact copy of Blackmagic’s algorithm?
No. The independent lab illustrates two sources, a required key and blending. Resolve’s actual tracker and procedural rendering only run in Resolve.
Sources, scope and what was actually verified
Control meaning and workflow were checked against the DaVinci Resolve 21 reference, while PNG names and visible UI were checked against eight unmodified images in the supplied site archive. The laboratory is an independent mathematical illustration. There has been no live Resolve 21 run or end-to-end Next.js build in this delivery.