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V1.4 - Geometry Editing

Correcting Image Geometry

This section deals with the tools and methods used for changing the projection of the panorama, manipulating the individual images that make up the panorama, changing perspective (which involves 'moving round' the panorama and relocating the horizon) and reframing the panorama (cropping). Whereas reframing is a simple action, changing perspective requires more understanding in order to get the results you expect.

There are two ways to approach the perspective problem:

  • the trial and error method, based on the initial output of Autopano Pro as displayed in the Editor Window and then fiddling around with the settings until you get a satisfying result.
  • gaining an understanding of the mechanics behind the process, knowing what modifications are available and the results that you can expect from each of them.

Autopano Pro is well suited to the “trial and error” method as it will quickly update the panorama preview based on the changes that you make. Even better is gaining an understanding of what exactly each modification does, which is what you should be aiming for, as it will allow far quicker manipulation of the image and less time spent blindly trying out different settings, which means that you will be able to get more work done more quickly.

To graps this topic more quickly, you should consult the Understanding Projecting Modes page, which describes the different projection modes available in Autopano Pro and how they work.

The Tools

  • Projection: Proj0 plan.png Proj0 cylindre.png Proj0 sphere.png
  • Image Mode: Layer mode off.png Layer on.png
  • Rotate: Rot180.png Rot90left.png Rot90right.png Yawpitchroll.png
  • Crop: Fit.png Crop.png
  • Point of View: Cross center.png Level.png Vertical1.png

Projection Modes

  • Proj0 plan.png Linear Projection
    • Advantages: always a good choice when working with a small FOV (field of view), recommended for architecture as it is the only projection mode that will not curve any line (the other two modes will always, to a certain extend, “bend” curbs and building tops).
    • Downside: in theory this mode can only be used if the FOV is smaller than 180°, determined by the diagonal of the image. In real world situation the limitation is actually 90° as the stretching produced on both edges of the image is already visible at 90°, and even more pronounced at the corners. Passed 120°, the results become unacceptable as the stretching will produce a significant and uncomfortable loss of sharpness.
      Icon-tips-24.png Tip: in certain architecture cases it may be better to use Linear Projection despite the excessive stretching and then cut away those part, leaving only the less deformed center of the panorama.
  • Proj0 cylindre.png Cylindrical Projection
    • Advantages: can handle horizontal FOVs up to 360°.
    • Downside: all straight lines parallel to the horizon (curbs, building tops) will, to various extents, be bent. The vertical angle is limited, it MUST be smaller than 180°, but a stretching will start to appear at the top and at the bottom of the image passed 45° from the horizon (over and down).
      Icon-tips-24.png Tip: when stitching long landscape panoramas, you may want to use Cylindrical instead of Spherical projection, in order to have a better width:height ratio (ie a bit taller panoramas). The main problem with long panoramas is that they look "squashed" and Cylindrical projection can help with that.
  • Proj0 sphere.png Spherical Projection
    • Advantages: this is the default choice as it can handle any panorama type. This mode is the default projection mode when opening the Editor Window; this is also the default mode when launching a rendering without going through the Editor Window.
    • Downside: for a direct display on a computer screen (without using a special viewer) or to print the panorama, you must first make sure that the amount of curvature of the lines parallel to the horizon stays acceptable. There is no set rule to determine what is acceptable and what’s not, you must use your best judgment. When the vertical field of view is large, the stretching of the top of the image (close to the zenith) and of the bottom of the image (close to the nadir) can vary from very natural to quite unnatural.

The Tools

Layer mode off.png Layer View Mode Layer on.png

The Layer View mode will let you visualize how the original images are arranged in the panorama. Activate the Layer View mode by clicking the button, next run your mouse pointer over the panorama to see the actual picture located under the pointer’s location. If the cursor is on top of an overlap (i.e. stitch seam), use the mouse wheel to scroll through the different pictures overlapping at the current location.

When the mouse pointer is located outside of the panorama area, the whole panorama is shown (i.e. the resulting stitched image with brightness, contrast and colors adjusted on the overlaps).

Another click on the button will exit the Layer View mode.

Icon-tips-24.png Tip: The task bar displays information related to the current selection (i.e. the selected source image): number and file name. This is often useful to identify an image we want to exclude from the panorama using the Control Point Editor.

Rotations: 90° Left Rot90left.png, 90° Right Rot90right.png, 180° Rot180.png

These three buttons let you rotate the panorama, which is usefull when the original source photos used to create the panorama have a wrong landscape/portrait orientation in their EXIF data, or no EXIF data at all. Note that often, despite the panorama appearing to be properly aligned after stitching, rotating it 90° will not result in a flat panorama - instead it may take the shape of a wave. It is therefore good practice to use the Auto Level tool after a 90° rotation.

Actions


Yawpitchroll.png Numerical Transformation

Numerical transformation

As surprising as it may sound this tool can by itself perform all the panorama modifications allowed by the following tools.

  • 180° Flip
  • 90° Left rotation
  • 90° Right rotation
  • Set Center Point
  • Auto Level
  • Set Verticals

Though experience you will learn how to use these tools far quicker and with better understanding than if you were to just read the theory here, so we advise you to stitch the example pictures provided with Autopano Pro and to alter the values of the three different parameters (yaw, pitch and roll) one by one, by, for example, +10° and then -10°, in order to get a better "feel" for each parameter. Remember that you should only alter one parameter at a time while learning, and never all three of them at once! You are doing this in order to understand what to expect from each modification and to be able to conduct large as well as precise changes, much more precise than possible using the mouse. Try this out first using a Spherical Projection and then with the other projection types.

Options

  • Yaw = Rotate left and right (a positive value moves the panorama to the right).
  • Pitch = Rotate up and down (a positive value moves the panorama down).
  • Roll = Rotation around the set center point (a positive value rotates the panorama clockwise).

The panorama's center is set using the "center point" button. Assuming you have the option "center point" enabled under the "view" menu in the Panorama Editor window, the center point is where the vertical and horizontal grey lines displayed over the panorama intersect.

The rotation angle is in degrees, the effects of this parameter are cumulative: a -10° rotation cancels a previous 10° rotation.

A random use of this tool makes it difficult to understand as the effects are cumulative, this would be an unfortunate approach as it is a very powerful tool.

Actions

  • To validate, press Enter or click on Check on.png: the panorama preview is adjusted according to what you defined.
  • To not take the modifications into account and go back to the previous state, click on Check off.png.
  • To cancel the modifications after having validated them, use the actions history clicking on History.png.


Cross center.png Set Center Point

Set center point

This tool sets the center point of the panorama in the spot where you click the mouse cursor, implying two things:

  • it moves the center of the panorama left or right (the vertical grаy line act as a guide).
  • it locates the horizon at the click’s height (the horizontal grаy line act as a guide).

(make sure you have the option "center point" enabled under the "view" menu in the Panorama Editor window in order to see these lines.)

Note that when using Planar Projection the perspective paths are affected by the location of the vertical grаy line.

When setting the vertical center (i.e. placing the horizon at the location of the horizontal grey line), the click location should be located at the camera's height as it was while photographing, unless you are looking for a low angle shot (verticals converging up) or a high angle shot (verticals converging down). So if your camera was standing in a field, with the center of the lens pointing towards the door of a cottage, click on the door of the cottage in the panorama to have the same angle set for your pano as you say while shooting.

To move the horizon up or down it is best to use the Set Verticals tool described in the next paragraph, or to alter the "yaw" parameter in the Numerical Transformation tool described earlier. Altering this yaw parameter is especially advised when working on a Cylindrical or Planar Projection as it will only offset the pano to the left or right without altering anything else.

Autopanо Pro will automatically estimate the location of the horizon before displaying the preview. If you made changes but afterwards decide that the default estimation was better, you can click on Auto Level to go back to the estimated value calculated by Autopano Pro. This being said, it is important to keep in mind that Autopano Pro totally ignores what was photographed. You remain the best judge to determine what is right.

Actions

  • If you click on "center point tool stays activated after use", you can try several center points without having to reactive the tool after each use.
  • To cancel the modifications after having validated them, use the actions history clicking on History.png.


Vertical1.png Set Verticals

Set verticals

This tool will allow you to straighten-up a panorama by placing vertical lines objects in the panorama that are supposed to be vertical.

How to use this tool:

  • Click on the Set Verticals tool, move your pointer over the preview then click and hold the left mouse button and drag the mouse to create a straight line.
  • Align this line parallel to the edge of a vertical object, e.g. place it vertically along a street lamp, the edge of a skyscraper, or the edge of a door or window. Two or three lines are generally enough, especially if they are placed far apart from each other, but you can use more. Be careful not to place these lines along old building walls or telephone poles that could have been leaning in real life! Once placed, the software will then find the best possible compromise, taking in account your input and the bonds created between the source photographs.

The yellow dotted line attached to the blue line is used to straighten the horizon. In landscape or nature photography is it quite frequent to shoot a subject with no verticals, when very often this subject will have a horizon. So instead of using a vertical as a guide you can adjust the verticals by placing the yellow dotted line on the horizon. The use of 3 or 4 lines on the horizon is generally enough to correct the panorama.

You can use the verticals tool with a single line to do a quick and precise rotation; the line you traced will then become a perfect vertical. You can use this as a trick to rotate a very wide panorama so that the left and right edge of an object, like the horizon, will be on the same horizontal level. You may want to resort to this trick sometimes as using the verticals tool precisely rotate a long panorama very a few degrees is very difficult. Lets assume we have a desert pano with a very wavy horizon because of all the dunes. Using the verticals tool is very difficult as we have to guess the horizon's real position. To make this task easy, use the trick: click the verticals tool on the left edge of the horizon in the panorama, and then drag it to the right edge of the object that you want to be horizontal to the left edge, in our case the wavy horizon. This will flip your panorama sideways, but also align those two points vertically. In order to get your panorama back to the horizontal state, just use the "90° Rotate" button, or in the Numerical Transformation tool input a value of 90° in the Rotate field.

Note: The blue line should be created from top to bottom to apply a transformation to the panorama. If the blue line is made horizontally the panorama will rotate a quarter of a turn; if made from bottom to top the panorama will flip 180 degrees.

Options

The horizontal line tool enables you to straighten a leaning horizon, but it is only available in the Planar Projection mode. It works just like the vertical lines tool: just draw a line on the part meant to be horizontal. If you wish to remain in spherical or cylindrical projection mode, then use the yellow dotted lines of the vertical lines tool to locate the horizon.

Actions

  • To erase a line, click on it and press the Suppr key.
  • To modify the orientation or length of a line, click on it and use the red squares located on the line's extremities.
  • To validate, press Enter or click on Check on.png: the panorama preview is adjusted according to what you defined.
  • To not take the modifications into account and go back to the previous state, click on Check off.png.
  • To cancel the modifications after having validated them, use the actions history clicking on History.png.

Find out more

Icône-VIDEO.gif Learn how to straighten a panorama using the vertical lines tool.


Level.png Auto Level

Even if the original pictures were shot with the lens pointing up or down Autopano Pro will often produce a leveled panorama, to a point where one could think that this tool doesn't work, as there is no visible difference between “before” and “after”!

If, in the other hand, the previous Yaw, Pitch and Roll tools were used to modify the panorama and/or if the center point was relocated, the effect of the Auto Level tool becomes visible.

Although Autopano Pro tries it’s best to produce acceptable results, it does not always succeed:

  • if the rotation axis of the camera wasn’t vertical when going from one shot to the other (handheld shots, tripod axis or panohead axis not well set) it is possible that parts of the resulting panorama will not be straight.
  • if all the pictures are leaning in the same direction (with a panohead this should not arise, with a tripod it's a difference between two settings), the whole panorama will not be straight.

In both cases the Set Verticals tool should be used to straighten everything up.

Actions


Crop.png Crop

Crop

This tool will allow you set the framing of the panorama. It works in the very same way as the Adobe Photoshop crop tool except that the original setting is automatically set to the maximum rectangular surface of the panorama. None of the rectangle’s surface is left empty; the automatic framing is quick and precise. Note: there's an exception to this rule (see example), when there's a small empty area near the edge of the panorama. Autopano Pro assumes such "holes" are easy to fix with Clone Stamp or other means and leaves them inside the final crop.

Options

  • Crop zone : In this part you can modify the cropping precisely:
    • Theta is for the rectangle width
    • Phi is for the rectangle height
    • Rotation enables to affect a rotation angle to the rectangle
    • Full sphere enables to crop the panorama in the case it is a part of a full spherical panorama (case of some virtual tours)
  • Ratio let you define a cropping ratio, which can be helpful if you wish to print and frame the panorama, or if you wish to keep the same cropping ratio for a series of panoramic images.
  • Opacity let you define the opacity of the zone outside the rectangle, to help you crop the panorama.

Actions

  • If you wish to resize the reclangle, use the squares arout it. If you press the Ctrl key, the resize is done from the rectangle center.
  • You can move the rectangular marquee by placing the mouse pointer inside the marquee, and with a click/hold action move it over the surface of the image.
  • You can rotate the rectangular marquee by placing the mouse pointer outside of the marquee area, and with a click/hold action rotate it over the surface of the image.
  • To validate, press Enter or click on Check on.png: the panorama preview is adjusted according to what you defined.
  • To not take the modifications into account and go back to the previous state, click on Check off.png.
  • To cancel the modifications after having validated them, use the actions history clicking on History.png.

Fit.png Auto Fit

When you press this button, the produced effect is the exact opposite of the one produced by the Crop tool: the panorama is included in a rectangle as big as needed to include all the pixels of the panorama.

If you previously used the Crop tool, then modified the panorama’s geometry, by let’s say applying a rotation, this tool is useful to recover the areas that are now excluded from the image.

As long as this button stays down, the totality of the resulting image will remain visible, whatever you do.