Optical Flow
Updated: 4 Dec 2023
Analyses an image and visualise the movement of objects in the scene.
Optical Flow
Method #
This node attempts to analyse an image and visualise the movement of objects in the scene, using different techniques depending on the mode selected.
Parameters
These properties control the core behaviours of the node.
Parameter Details Preview In Viewport Preview the generated image as an overlay in the viewport.
- Off : No preview is generated.
- RGBA : Preview the image blended with alpha in the viewport.
- RGB : Preview the colour channels in the viewport.
- Alpha : Preview the alpha channel in the viewport.
- PIP : Preview the image blended with alpha in the viewport, in a smaller picture in picture display, on top of the existing content.
Apply PostFX Before Alpha Image Input (Legacy) When enabled, the alpha input image is applied after the postfx pass, overwriting any effects the postfx would have applied to the alpha channel.
Previous Frame Blend How much of the previous frames blend with the current frame.
Previous Frame Directional Dependence How much the directional movement of the previous frame affects the current frame.
Num Levels How many levels of motion can be tracked.
Optical Flow Mode Change the way the optical flow motion is calculated.
- High Quality : Uses a block matching algorithm for reasonably accurate tracking.
- Motion Vector Estimate : Generates smoother motion vectors but far less accurate.
- High Speed : A simple technique using gradients and frame differences. less accurate than high quality, but much faster.
Output Velocity Magnitudes Forces the output to only show the magnitude. this only affects the output image, and not the internal motion vectors.
Output Velocity Angle And Magnitude Outputs both the velocity angle and magnitudes. this only affects the output image, and not the internal motion vectors.
Optical Flow Scale Scale the movement that is output.
Num Dilate Passes How many times the dilate pass is run.
Inputs
These properties control the core behaviours of the node.
| Parameter | Details |
|---|---|
| Preview In Viewport | Preview the generated image as an overlay in the viewport.
|
| Apply PostFX Before Alpha Image Input (Legacy) | When enabled, the alpha input image is applied after the postfx pass, overwriting any effects the postfx would have applied to the alpha channel. |
| Previous Frame Blend | How much of the previous frames blend with the current frame. |
| Previous Frame Directional Dependence | How much the directional movement of the previous frame affects the current frame. |
| Num Levels | How many levels of motion can be tracked. |
| Optical Flow Mode | Change the way the optical flow motion is calculated.
|
| Output Velocity Magnitudes | Forces the output to only show the magnitude. this only affects the output image, and not the internal motion vectors. |
| Output Velocity Angle And Magnitude | Outputs both the velocity angle and magnitudes. this only affects the output image, and not the internal motion vectors. |
| Optical Flow Scale | Scale the movement that is output. |
| Num Dilate Passes | How many times the dilate pass is run. |
| Name | Description | Typical Input |
|---|---|---|
| Effect Mask | Mask out areas that Post-FX applied to this node won’t be applied. | Loader |
| Alpha Image | Use a separate video nodes luminance values to overwrite the alpha channel of the image. | Loader |