The General Panini Projection - Revision history

Tksharpless: /* Very Wide and Ultra-Wide Views from Panoramas */

2010-07-11T01:18:21Z

‎Very Wide and Ultra-Wide Views from Panoramas

Tksharpless: /* Very Wide and Ultra-Wide Views from Panoramas */

2010-07-11T01:09:55Z

‎Very Wide and Ultra-Wide Views from Panoramas

Tksharpless: /* Perspective Views from Fish-Eye Photos */

2010-07-11T01:00:41Z

‎Perspective Views from Fish-Eye Photos

Erik Krause: categorized

2010-06-25T13:22:35Z

categorized

Tksharpless at 03:15, 22 June 2010

2010-06-22T03:15:26Z

Tksharpless at 03:12, 22 June 2010

2010-06-22T03:12:43Z

Tksharpless: /* Software Versions */

2010-06-22T02:53:20Z

‎Software Versions

Tksharpless: /* Ultra-Wide Views from Panoramas */

2010-06-22T02:44:13Z

‎Ultra-Wide Views from Panoramas

Tksharpless at 02:00, 10 April 2010

2010-04-10T02:00:45Z

Tksharpless: /* Perspective Views from Fish-Eye Photos */

2010-04-10T01:45:46Z

‎Perspective Views from Fish-Eye Photos

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 [[File:Pantheon-150x100-rect-panini.jpg|right|360px]]
-With a panorama as the source image, the general Panini projection can be used like any other projection to render views in various directions.  However it is best for views where the line of sight is not tilted strongly up or down.  It is important to align the vertical direction carefully, in both "pitch" and "roll" (for example by dragging the image in Hugin's fast preview window).  To get a perfectly framed view, it may be necessary to render oversize and crop later.
+With a panorama as the source image, the general Panini projection can be used like any other projection to render views in various directions.  However it is best for views where the line of sight is not tilted up or down.  It is important to align the vertical direction carefully in "roll" as well.  Both pitch and roll alignment can be done by dragging the image in Hugin's fast preview window.  To get a perfectly framed view, it may be necessary to render oversize and crop later.
-The image at right compares rectilinear (top) and general Pannini (bottom) projections of a panoramic view 150 degrees wide by 100 degrees high in the Pantheon (Rome), a large, perfectly circular space.  The point of view here is well away from the middle of the room.  Notice how the Pannini perspective both magnifies the center and condenses the edges, so that the people in the middle look closer and the people near the edges  look more natural -- for example, the man taking a picture at far right.  A 50 percent "soft squeeze" has been applied at both top and bottom to improve the perspective of the floor and dome.
+The image at right compares rectilinear (top) and general Pannini (bottom) projections of a panoramic view 150 degrees wide by 100 degrees high in the Pantheon (Rome), a large, perfectly circular space.  The point of view here is well away from the middle of the room.  Notice how the Pannini perspective both magnifies the center, so that people in the middle look closer, and condenses the periphery, so that people near the edges have more natural shapes -- for example, the man taking a picture at far right.  A 50 percent "soft squeeze" has been applied at both top and bottom to improve the perspective of the floor and dome.
 It is often possible to render a convincing view more than 180 degrees wide, if the subject has a strong central perspective.  The spectacular image of the main concourse at New York's Grand Central Station, below, is 220 degrees wide.  The slanted walls at the sides are actually the ends of a transverse wall that stands well behind the point of view.  This is a standard Pannini projection without any "squeeze".

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 [[File:Pantheon-150x100-rect-panini.jpg|right|360px]]
-With a panorama as the source image, the general Panini projection can be used like any other projection to render views in various directions.  However it is best for views where the line of sight is not tilted strongly up or down.  It is important to align the vertical direction carefully (for example by dragging the image in Hugin's fast preview window).  To get a perfectly framed view, it may be necessary to render oversize and crop later.
+With a panorama as the source image, the general Panini projection can be used like any other projection to render views in various directions.  However it is best for views where the line of sight is not tilted strongly up or down.  It is important to align the vertical direction carefully, in both "pitch" and "roll" (for example by dragging the image in Hugin's fast preview window).  To get a perfectly framed view, it may be necessary to render oversize and crop later.
-The image at right compares rectilinear (top) and general Pannini (bottom) projections of a typical panoramic view 150 degrees wide by 100 degrees high in the Pantheon (Rome).  Notice how the Pannini perspective both magnifies the center and condenses the edges, so that the people in both regions look more natural.  A 50 percent "soft squeeze" has been applied at both top and bottom to improve the perspective of the floor and dome.
+The image at right compares rectilinear (top) and general Pannini (bottom) projections of a panoramic view 150 degrees wide by 100 degrees high in the Pantheon (Rome), a large, perfectly circular space.  The point of view here is well away from the middle of the room.  Notice how the Pannini perspective both magnifies the center and condenses the edges, so that the people in the middle look closer and the people near the edges  look more natural -- for example, the man taking a picture at far right.  A 50 percent "soft squeeze" has been applied at both top and bottom to improve the perspective of the floor and dome.
-It is often possible to render a convincing view more than 180 degrees wide, if the subject has a strong central perspective.  The spectacular image below is 220 degrees wide; the slanted walls at the sides are actually the ends of a transverse wall that stands well behind the point of view.  This is a standard Pannini projection without any "squeeze".
+It is often possible to render a convincing view more than 180 degrees wide, if the subject has a strong central perspective.  The spectacular image of the main concourse at New York's Grand Central Station, below, is 220 degrees wide.  The slanted walls at the sides are actually the ends of a transverse wall that stands well behind the point of view.  This is a standard Pannini projection without any "squeeze".
 [[File:C Marchi-GrandCentral-adj.jpg|thumb|center|800px|Grand Central Terminal by Cristian Marchi; Panini projection, hFOV 220 degrees]]

← Older revision		Revision as of 01:00, 11 July 2010
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	If vertical lines look curved, you should adjust the lens focal length or FOV until they are straight. Temporarily switching to the rectilinear projection may make it easier to do this. The curvature results when the panotools lens model does not match the actual projection function of your lens. Adjusting the fov provides a first order correction that is usually 'close enough'; but for even better results, you could set the lens fov and a,b,c distortion parameters to values that were optimized on a well-aligned spherical panorama made with the same lens.		If vertical lines look curved, you should adjust the lens focal length or FOV until they are straight. Temporarily switching to the rectilinear projection may make it easier to do this. The curvature results when the panotools lens model does not match the actual projection function of your lens. Adjusting the fov provides a first order correction that is usually 'close enough'; but for even better results, you could set the lens fov and a,b,c distortion parameters to values that were optimized on a well-aligned spherical panorama made with the same lens.
		+
		+	{{clr}}

	=== Very Wide and Ultra-Wide Views from Panoramas ===		=== Very Wide and Ultra-Wide Views from Panoramas ===

← Older revision		Revision as of 13:22, 25 June 2010
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−	The general Panini projection is an adjustable projection that can render convincing simulated perspective views of scenes up to 150 degrees wide, or even wider in some cases. It was first implemented in early 2009 in the panorama viewer, Panini, and in limited form in the panotools library. This page describes the improved version that was added to the panotools library in January 2010, and to PTStitcherNG in February 2010.	+	The general Panini projection is {{Glossary\|an adjustable projection that can render convincing simulated perspective views of scenes up to 150 degrees wide, or even wider in some cases\|1}}. It was first implemented in early 2009 in the panorama viewer, Panini, and in limited form in the panotools library. This page describes the improved version that was added to the panotools library in January 2010, and to PTStitcherNG in February 2010.

	The Pannini projection is a cylindrical projection, so it keeps vertical straight lines straight and vertical. Unlike other cylindrical projections, it keeps radial lines through image center straight as well. Those two kinds of straight lines are the most important perspective cues in many scenes, so a Pannini view often resembles a normal rectilinear perspective. But the horizontal field of view can be very wide, without the peripheral distortion (stretching) that is so noticeable when a rectilinear perspective is pushed too far.		The Pannini projection is a cylindrical projection, so it keeps vertical straight lines straight and vertical. Unlike other cylindrical projections, it keeps radial lines through image center straight as well. Those two kinds of straight lines are the most important perspective cues in many scenes, so a Pannini view often resembles a normal rectilinear perspective. But the horizontal field of view can be very wide, without the peripheral distortion (stretching) that is so noticeable when a rectilinear perspective is pushed too far.

← Older revision		Revision as of 03:15, 22 June 2010
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−	The general Panini projection is an adjustable projection~~, or more properly a parameterized family of projections,~~ that can render convincing simulated ~~perspectives on fields~~ of ~~view~~ up to 150 degrees wide, or even wider in some cases. It was first implemented in early 2009 in the panorama viewer, Panini, and in limited form in the panotools library. This page describes the improved version that was added to the panotools library in January 2010, and to PTStitcherNG in February 2010.	+	The general Panini projection is an adjustable projection that can render convincing simulated perspective views of scenes up to 150 degrees wide, or even wider in some cases. It was first implemented in early 2009 in the panorama viewer, Panini, and in limited form in the panotools library. This page describes the improved version that was added to the panotools library in January 2010, and to PTStitcherNG in February 2010.

	The Pannini projection is a cylindrical projection, so it keeps vertical straight lines straight and vertical. Unlike other cylindrical projections, it keeps radial lines through image center straight as well. Those two kinds of straight lines are the most important perspective cues in many scenes, so a Pannini view often resembles a normal rectilinear perspective. But the horizontal field of view can be very wide, without the peripheral distortion (stretching) that is so noticeable when a rectilinear perspective is pushed too far.		The Pannini projection is a cylindrical projection, so it keeps vertical straight lines straight and vertical. Unlike other cylindrical projections, it keeps radial lines through image center straight as well. Those two kinds of straight lines are the most important perspective cues in many scenes, so a Pannini view often resembles a normal rectilinear perspective. But the horizontal field of view can be very wide, without the peripheral distortion (stretching) that is so noticeable when a rectilinear perspective is pushed too far.

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 The general Panini projection is an adjustable projection, or more properly a parameterized family of projections, that can render convincing simulated perspectives on fields of view up to 150 degrees wide, or even wider in some cases.  It was first implemented in early 2009 in the panorama viewer, Panini, and in limited form in the panotools library.  This page describes the improved version that was added to the panotools library in January 2010, and to PTStitcherNG in February 2010.
-A Panini perspective seems to combine telephoto and wide angle views in one image.  Compared to a rectilinear view of the same width, the center is magnified and depth seems flattened (telephoto effects).  At the same time, the field of view can be very wide, without the peripheral distortion (stretching) that is so noticeable when a rectilinear perspective is pushed too far.  And somehow the view tends to look even wider than it actually is.
+The Pannini projection is a cylindrical projection, so it keeps vertical straight lines straight and vertical.  Unlike other cylindrical projections, it keeps radial lines through image center straight as well.  Those two kinds of straight lines are the most important perspective cues in many scenes, so a Pannini view often resembles a normal rectilinear perspective.  But the horizontal field of view can be very wide, without the peripheral distortion (stretching) that is so noticeable when a rectilinear perspective is pushed too far.
-The general Panini projection is suitable for subjects that have a lot of architectural content, especially interiors.  It works best for views with a single central vanishing point -- straight down a city street, or the aisle of a church, for example.  However it is good for oblique interior and street views too.  It is not suitable for close-up exterior views of buildings, especially when looking toward a corner of the building.
+The general Panini projection is suitable for architectural subjects, especially interiors.  It works best for views with a single central vanishing point -- straight down a city street, or the aisle of a church, for example.  However it is good for oblique interior and street views too.  It can make nice city-scapes, but is not suitable for close-up exterior views of buildings, especially when looking toward a corner of the building.
-For best results the general Panini projection should be used interactively: you adjust the control parameters until your image looks just right.  The 'fast' preview window in the 2010 version of hugin works well for that most of the time but has a few problems.  However, it is possible to get equally good results with the 'slow' preview window, and with experience, even with scripts for the command line tools, PTStitcherNG or PTmender.
+For best results the general Panini projection should be used interactively: you adjust the control parameters until the image looks just right.  The 'fast' preview window in the 2010 version of Hugin works well for that most of the time but has a few problems.  However, it is possible to get equally good results with the 'slow' preview window, and with experience, even with scripts for the command line tools, PTStitcherNG or PTmender.
 == Geometrical Description ==
 [[File:220x120deg-panini-grid.png|thumb|400px|Standard Panini projection, 10 degree intervals]]
-The basic Panini projection -- the cylindrical stereographic projection -- renders vertical, horizontal and diagonal straight lines as shown in the diagram at right.  Verticals are straight, a prerequisite for any perspective view.  Radial lines through the view center are also straight. That creates a convincing perspective illusion when there is a vanishing point at or near view center.  But horizontal straight lines are curves, with the strongest curvature in the middle of the image. That makes many images seem to 'bulge' at top and bottom center.
+The basic Panini projection -- the cylindrical stereographic projection -- renders vertical, horizontal and radial straight lines as shown in the diagram at right.  Verticals are straight, a prerequisite for any perspective view.  Radial lines through the view center are also straight. That creates a convincing perspective illusion when there is a vanishing point at or near view center.  But horizontal straight lines are curves, with the strongest curvature in the middle of the image. That makes many images seem to 'bulge' at top and bottom center.
 The general Panini adds two adjustable parameters to the basic projection.  One sets the horizontal angle compression, so the projection can vary smoothly from rectilinear to a highly condensed form.  The other reduces the curvature of horizontal lines.  This can make many central perspectives look more natural, and can also improve the perspective illusion when the vanishing point is off-center.  We call this a 'squeeze' parameter because early implementations actually compressed the middle of the image; current versions stretch the sides instead.  The adjustment is purely vertical so that verticals remain straight. There are actually separate squeeze parameters for the top and bottom halves of the image.

← Older revision		Revision as of 02:53, 22 June 2010
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	Helmut Dersch's PTStitcherNG implements the general Panini projection just like libpano13. It only runs from scripts and provides no interactive preview; however it is so fast that an iterative adjustment of the script parameters is feasible.		Helmut Dersch's PTStitcherNG implements the general Panini projection just like libpano13. It only runs from scripts and provides no interactive preview; however it is so fast that an iterative adjustment of the script parameters is feasible.

−	-- T. K. Sharpless, 18 January 2010 - ~~09 April~~ 2010 --	+	-- T. K. Sharpless, 18 January 2010 - 21 June 2010 --

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 If vertical lines look curved, you should adjust the lens focal length or FOV until they are straight.  Temporarily switching to the rectilinear projection may make it easier to do this.  The curvature results when the panotools lens model does not match the actual projection function of your lens. Adjusting the fov provides a first order correction that is usually 'close enough'; but for even better results, you could set the lens fov and a,b,c distortion parameters to values that were optimized on a well-aligned spherical panorama made with the same lens.
-=== Ultra-Wide Views from Panoramas ===
+=== Very Wide and Ultra-Wide Views from Panoramas ===
-With a properly aligned panorama as the source image, the general Panini projection can be used like any other projection to render views in various directions.  However it is best for views where the line of sight is level, not tilted up or down.  You can use hugin's cropping feature to eliminate unwanted areas at the top or bottom, but to get a perfectly framed view it may be necessary to render oversize and crop later.
-It is often possible to render a convincing view more than 180 degrees wide, if the subject has a strong central perspective.  Because of the 'basic bulge' it is best to limit the vertical FOV on ulta-wide views.  Only a soft squeeze can be used here, as the hard squeeze has singularities (goes to infinity) at +/- 90 degrees.
+[[File:Pantheon-150x100-rect-panini.jpg|right|360px]]
-The spectacular image below is 220 degrees wide; the slanted walls at the sides are actually the ends of a transverse wall that stands well behind the point of view.
+With a panorama as the source image, the general Panini projection can be used like any other projection to render views in various directions.  However it is best for views where the line of sight is not tilted strongly up or down.  It is important to align the vertical direction carefully (for example by dragging the image in Hugin's fast preview window).  To get a perfectly framed view, it may be necessary to render oversize and crop later.
 [[File:C Marchi-GrandCentral-adj.jpg|thumb|center|800px|Grand Central Terminal by Cristian Marchi; Panini projection, hFOV 220 degrees]]

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 Hugin with the general Panini projection is an excellent 'de-fishing' tool.  Load a fisheye photo, adjust pitch and roll angles to align the true vertical with the vertical axis of the view, then adjust the general Panini parameters for a pleasing perspective -- anything from rectilinear to highly compressed and squeezed.  Note that you can adjust pitch and roll by dragging in the fast preview window.
-If vertical lines look curved in the general Panini projection view, you should adjust the lens focal length or FOV until they are straight.  Temporarily switching to the rectilinear projection may make it easier to get this adjustment right.  This curvature results when the panotools lens model does not match the actual projection function of your lens. Adjusting the fov provides a first order correction that is usually 'close enough for jazz'; but for even better results, you could set the lens fov and a,b,c distortion parameters to values that were optimized on a well-aligned spherical panorama made with the same lens.
+If vertical lines look curved, you should adjust the lens focal length or FOV until they are straight.  Temporarily switching to the rectilinear projection may make it easier to do this.  The curvature results when the panotools lens model does not match the actual projection function of your lens. Adjusting the fov provides a first order correction that is usually 'close enough'; but for even better results, you could set the lens fov and a,b,c distortion parameters to values that were optimized on a well-aligned spherical panorama made with the same lens.
 === Ultra-Wide Views from Panoramas ===