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# O_Solver

The O_Solver node defines the geometric relationship between the two views in the input images (that is, the camera relationship or solve). This is necessary when aligning footage with O_VerticalAligner. It is also required to calculate aligned disparity vectors, when using the alignment control in O_DisparityGenerator. O_Solver data is not necessary for colour and focus matching using O_ColourMatcher and O_FocusMatcher.

# Inputs and Controls

Connection Type | Connection Name | Function
Input | Camera | A pre-tracked Nuke stereo camera that describes the camera setup used to shoot the Source image. This can be a camera you have tracked with the CameraTracker node or imported to Nuke from a third-party camera tracking application. This input is optional.
Ignore | A mask that specifies areas to ignore during the feature detection and analysis. This can be useful if an area in the Source image is producing incorrectly matched features. This input is optional.
Source | A stereo pair of images. These can either be the images you want to work on, or another pair of images shot with the same camera setup.

Control (UI) | Knob (Scripting) | Default Value | Function
O_Solver Tab
Views to Use | viewPair | Dependent on source | Sets the two views you want to use to calculate the features and the camera relationship. These views are mapped for the left and right eye.
Analysis
Mask | ignore | None | Set the mask type to exclude areas of the sequence: • None - use the entire image area. • Source Alpha - use the alpha channel of the Source clip as an ignore mask. • Source Inverted Alpha - use the inverted alpha channel of the Source clip as an ignore mask. • Mask Luminance - use the luminance of the Ignore input as an ignore mask. • Mask Inverted Luminance - use the inverted luminance of the Ignore input as an ignore mask. • Mask Alpha - use the alpha channel of the Ignore input as an ignore mask. • Mask Inverted Alpha - use the inverted alpha channel of the Ignore input as an ignore mask.
Analysis Key | analysisKeyframe | 0 | Displays set keyframes from which O_Solver does the feature matching and analysis. The solves for all other frames are created by interpolating between the results on the keyframes on either side.
Delete Key | deleteAnalysisKey | N/A | Click to delete the analysis key at the current frame.
Delete All | deleteAnalysisKeys | N/A | Click to delete all analysis keys.
Key Frame | addAnalysisKey | N/A | Click to set an analysis key at the current frame.
Key Sequence | analyseSequence | N/A | Click to analyse the whole sequence automatically and set analysis keys when a change in camera alignment is detected. Tip: Key Sequence detects changes in camera alignment automatically, but can be time-consuming on longer sequences.
Key Nominated | analyseNominated | N/A | Click to set analysis keys at the frames specified in the Render dialog. You can specify frames using Nuke's regular frame expressions. For example, if you enter "1-5 8 10 15 22-25", only those 12 frames are keyed.
Single Solve From All Keys | singleSolve | disabled | When enabled, O_Solver calculates a single solve using all the keyframes you have set. Use this for rigs that don’t change over time to get more accurate results than when using a single keyframe or when the O_Solver analysis is performed on one clip and then re-used for another clip. Do not use this if there is jitter in the alignment or there is a change in separation, convergence, or zoom. Instead, use a separate solve for each keyframe and place keys where the alignment changes.
Display
Display | displayType | Keyframe Matches | Sets the display mode: • Nothing - show the Source image. • Keyframe Matches - show the features and matches for the camera relationship calculation in a Viewer overlay. Feature matches are only calculated for the keyframes. • Preview Alignment - shows the aligned matches at keyframes, but also calculates matches at non-keyframes, allowing you to review how well the interpolated solve works and whether additional keyframes are required.
Match Offset | offset | 100 | Sets the offset (in pixels) applied to the aligned feature matches. You can: • increase this value to artificially increase the disparity, so it’s easier to see how horizontal the feature matches are. • decrease this value to set the disparity of particular matches to zero and examine the vertical offset at each feature. The matches should sit on top of each other. Note: The Match Offset control is only available when Display is set to Preview Alignment.
Error Threshold | alignmentError | 3 | Sets the threshold on the vertical alignment error in pixels. When Display is set to Preview Alignment, any matches with a vertical error greater than the threshold are highlighted in the Viewer. This allows you to easily delete poor matches with large errors when previewing alignment at keyframes - adjust the Error Threshold to highlight poor matches and press Backspace to remove them.
Current Frame
Re-analyse Frame | resetFrame | N/A | Click to clear the automatic feature matches from the current frame and recalculate them. This can be useful if there have been changes in the node tree upstream from O_Solver, you have deleted too many automatic feature matches, or you want to calculate the automatic matches based on any user matches you have created.
Delete Auto Matches | deleteAutoMatches | N/A | Click to delete all automatically generated matches added to the current frame.
Delete User Matches | deleteUserMatches | N/A | Click to delete all feature matches you have manually added to the current frame.