# Hugin Optimiser tab

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As explained on the Hugin Photos tab, hugin uses a photo alignment scheme where it adjusts image orientation and lens settings of source photos until the control points line-up. This process is called (geometric) optimisation. Normally you will use the Hugin Assistant tab where control points are automatically generated, or use the Feature matching option from the Hugin Photos tab to generate control points.

You can manually create individual control points in the Control Points tab, and you can manage them in both the Photos tab and Control Points table.

# Geometric Optimizer

The pre-set optimisation options are useful for most situations, but sometimes it is necessary to switch to Custom parameters.

For example, when shooting hand-held panoramas, some of the position variation between shots can be resolved by using different d and e Image Center Shift parameters for each shot. Select Custom parameters, and pick the d and e parameters for optimisation on this hugin Optimiser tab.

Similarly, the translation parameters could be used to correct a wonky shot. However, they were meant for linear panoramas which expand to infinite distance at 180 degrees field of view, so you must make sure any images with non-zero translation (X, Y, or Z parameters) are in the middle of the panorama (y and p should all be around zero, and the field of view shouldn't be large enough to make them expand more than 180 degrees). This can be used to patch in the floor after you have removed the tripod that was obscuring it. You can take a shot of the floor where the tripod was at an angle (therefore you can avoid casting a shadow on the image in most cases). You can then optimise X,Y,Z on only this image. However, the floor must be flat for this to work, and this shot must be in the middle of the panorama. You can make down the middle by rotating the panorama on either of the previews. Alternatively you could try to optimize the translation plane parameters yaw and pitch to rotate the remapping plane into the right direction.

Be careful not to optimize more parameters than you need. This can cause problems. For example, when stitching a map or when all is on the same plane you don't need to optimize plane yaw/plane pitch. These variables should only used when there are several remapping planes in the pictures are needed (e.g. for patching a nadir image). For stitching images on the same plane, you have only one defined remapping plane.

The images list behaves very similar to the image list on the Photos tab. So you can also in this tab add or remove images, change the lens or stack assignments, link or unlink image variables, and so on. In addition to the features on the list on the Photos tab, it also provides in-place editing of single image variables. (Note: If you want to modify a value for a lens, you need to single-click the value, not double-click it.) If you want to change image variables from several images at once, select all affected images and choice Edit image variables... from the context menu.

## Image Orientation

Depending on the User Interface mode, you can modify:

- Yaw (y), Pitch (p) and Roll (r) in Simple and Advanced mode.
- Yaw (y), Pitch (p), Roll (r), TranslationX (TrX), TranslationY (TrY), TranslationZ (TrZ), Translation plane yaw (Tpy) and Translation plane pitch (Tpp) in Expert mode.

With Ctrl+Left click you define which parameters will be optimised. The context menu provides short cuts to select the parameters of all images, of all images of a selected lens or of all image of a single stack.

## Lens parameters

Depending on the User Interface mode, you can modify:

- Radial distortions (a, b, c) and horizontal and vertical image center shift (d, e) in Simple and Advanced mode.
- Radial distortions (a, b, c), horizontal and vertical image center shift (d, e) and horizontal and vertical image shearing (g, t) in Expert mode.

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