gus
Posts: 563
Location: United Kingdom
Registered: 19 Jun 2007
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PTgui templates
Posted: 30 Jan 2008 at 10:38 GMT
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I wish to use my D70s 10.5mm, NN3 combo more effectively, and understand that creating a template from a pano with lots of control points is the way to go.
Can someone out there exlain to us newbies how to go about creating a template, how to optimise the different paramaters and how to apply this template?
Ive searched the forum, but most of the posts pertain to previous versions of Ptgui.
Also, do I need to create a template for each sequence scenario : ie 6+t+b vs 6+t vs 6+B vs 6 only?
And how accurately would the rotation angle have to be, in other words if the template pano was done in 60' increments, do the panos that the template is being applied to have to be EXACTLY 60 degrees, or can it be within 57-63' say?
Thanks in advance!
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John Houghton
Posts: 3411
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: PTgui templates
Posted: 31 Jan 2008 at 8:17 GMT
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A template is simply a PTGui project file. After loading a set of images into PTGui, a template is applied using File->Apply template. It will copy in lens and image parameters and also a crop circle if applicable. Control points are not copied over.
Making a template is a matter of shooting a set of images and stitching them, but with more than the usual care and attention to detail:
1. Choose a venue that is rich in features for assigning control points in all directions - the larger the better, as this ensures that parallax errors will not be an issue.
2. Set up the camera on the pano head as accurately as you can with the lens at the no parallax point.
3. Take a full set of images including zenith and nadir with the camea on the head for all.
4. Stitch the images manually. You don't need a large number of control points per seam, but they do need to be accurately placed and spread out reasonably evenly along the full length of the overlapped areas. The automatic control point generator is inclined to cluster the points in the middle, which is something to be avoided when calibrating the lens parameters, as here.
5. Follow the optimization instructions in my post at www.panoguide.com/forums/qna/3004 (Mar 28, 19:26). This was for a circular fisheye, but a fullframe fisheye is similar (no crop, of course, and 6 horizontal instead of 4). You can set the hfov intitially to 87.1 degrees (portrait orientation), and lens parameter b to -0.015.
Save the project file for use as a template. You would need to adapt the project for different combinations of images, but you can apply a 6+Z+N template to 6 horizontal shots, or to 6+Z without any problems. You can make a 6+N template by deleting the zenith from the 6+Z+N project.
Obviously, if you are using different pitch angles for the horizontal shots to minimize holes at the nadir or zenith in these alternative templates, then you should really shoot new panoramas for these configurations so that the y,p,r values are correct - essential if you have a highly accurate head and want to stitch with templates without assigning control points. The important thing here is that the y,p,r values need to be set with high repeat accuracy. It doesn't matter the yaw angles are not individually exactly 60 degrees; they just need to be exactly the same in sequence to match the template vaues. So care needs to be taken to ensure the same detent position is used for each shot as was used for the template.
Note that when stitching with a template and assisted with control points, you can manage with only a few points per seam (as few as 2 per seam if need be when features are scarce, but 4 spread out would be preferable). The lens parameters a,b,c should not generally be optimized, especially if control points are are few and not well spread out.
John
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