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Thread: Output a panoramic stretched to edges?

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Andrei2k

Posts: 5
Location: United States
Registered: 15 Mar 2014
Output a panoramic stretched to edges?
Posted: 15 Mar 2014 at 3:56 GMT
Hello,

I have been doing panoramic photos for years but recently have wanted to output them stretched to the edges so that when wrapped to a sphere the poles are as clean and distortion free as possible. Basically I know that a polar to rectangular is the calculation if coming from a sphere to rectangle and I need the opposite. All of the various projection types and outputs leave me with the wavy edges which most crop but I need the corners that go in to be stretched out to a flat edge on all sides.


I hope this is clear but if not I can hunt down some examples of what I want to achieve.

Thank you in advance,
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: Output a panoramic stretched to edges?
Posted: 15 Mar 2014 at 7:48 GMT

Andrei2k said:

I hope this is clear but if not I can hunt down some examples of what I want to achieve.

It's not clear what you want to do. Some examples would help to avoid a lot of conjecture.

John
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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Output a panoramic stretched to edges?
Posted: 16 Mar 2014 at 7:32 GMT
Conjecture:

I think he wants to take a rectangular picture and turn it into an equirectangular picture for use in a spherical panorama.

Much easier to go from a equirectangular image to a rectangular image (crop out the center section) than the other way.

A Equirectangular picture is exactly twice as wide as it is tall. Once you modify your rectangular picture to these dimensions by filling in the top and bottom, the result may still not look right.

Better to convert your rectangular image into a cynlindrical pano.

We need examples.
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Andrei2k

Posts: 5
Location: United States
Registered: 15 Mar 2014
Re: Output a panoramic stretched to edges?
Posted: 19 Mar 2014 at 13:38 GMT
updated: 19 Mar 2014 at 13:40 GMT
Thank you for the replies so far. Sorry if it wasn't clear, yes I believe equirectangular is what I want to achieve.

I know cropping the center out is easy and thats what I have been doing so far. Here is a page with examples of the result I need. I realize there is heavy distortion at the poles (top and bottom edge) but I need this to go rectangular to polar and form as perfect of a spherical wrap as possible.

www.doschdesign.com/products/hdri/Outdoor_Photo_S...

www.doschdesign.com/products/hdri/Surroundings.ht...

Thank you for help so far,
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: Output a panoramic stretched to edges?
Posted: 19 Mar 2014 at 19:14 GMT
The examples you refer to at the links are full 360x180 equirectangular images that represent the entire spherical view as seen from one point. By their very nature, they will wrap exactly onto a sphere. This being what you want to achieve, you need to take several photographs (regular rectangular photos) that together cover the entire view and stitch them together. Just one photo can only cover an angle of view of around 120 degrees, so cannot be transformed to cover the entire surface of a sphere. Of course, if you simply crop any rectangular image to a 2:1 aspect ratio, it can be wrapped exactly around a sphere by pretending it is an equirectangular image. But this is not going to look very nice.

John
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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Output a panoramic stretched to edges?
Posted: 20 Mar 2014 at 2:22 GMT
"But this is not going to look very nice."

That is about as politically correct as you can get. The words I would use to express my opinion of the result would be rather harsh and not for sensitive ears. Well stated John.
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Andrei2k

Posts: 5
Location: United States
Registered: 15 Mar 2014
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 3:42 GMT
Hey John thank you so much for your reply. There are some good tips there but I think I need to know a bit more to achieve the morphing process.

The reason I need to achieve this as the samples I provided is for visual effects purposes.

With all due respect Dennis, I could really care less how it looks 'as is' since I want to learn the process of the stretching for the integrated process of HDR spheres in visual effects.

Once I capture the images without more the 120 degree fov and stitch them I still am confused about how to stretch the result to the edges like in the examples.

Thank you.
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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 6:20 GMT
updated: 22 Mar 2014 at 6:30 GMT
Andrei2k,

You "stitch" multiple images together, you do not stitch a few then stretch to the desired dimensions.

The stretching you see in the examples you linked to are images that have been stitched together right before the publishing step. They have not been stretched.

Depending on the lens you use, you take enough pictures to cover the entire inside of a sphere. For a Nikon 10mm lens on a cropped sensor camera, you would shoot 6 pictures around horizontally, 1 straight up ( or at 60 degrees, depends on personal taste) and 1 straight down, remove the camera from the rig, move the rig out of the way and shoot another one straight down hand held.

On a full frame sensor camera the Tamron 10-17mm lens set at 12mm requires 4 shots around tilted up 5 degrees and 1 shot hand held straight down.

Your stitching software combines the images all together to form the "stretched" images.

Your publishing software, like Pano2vr, creates the necessary script files and other supporting files that allow the final image to be viewed interactively and not as a flat image as shown in your examples.

It is that simple.

If you do not take enough pictures to cover the entire sphere, any manual "stretching" will render the picture useless when viewed as a sphere due to user induced distortion.

Individual images taken with a D300 + Sigma 8mm fisheye lens:

stitched to form:

If you set the initial FOV correctly, when opened in a proper viewer the illusion will be a web cam that you can control is floating in space over a fixed point:
www.dlsphoto.net/Europe2009/Paris/Eiffel_Tower/To...

You can then crop out the center section in an attempt to return to a cylindrical pano:
This is the image I use for my wallpaper across my two monitors.


If you try to stretch the cropped photo back out, you are filling in the missing information with invalid pixels and the resulting pano will look horrible. You need to start with the entire scene photographed, then stitch.

Stitched, not stretched.

All that being said, if all you ever want to do is display the flattened image, Photoshop has many distortion features that will allow you to expand a picture and create the illusion the image is a full spherical image.

Dennis
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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 6:41 GMT
If your stitching software can output a "cross", Pano2VR can easily wrap this output into a sphere.

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Smooth

Posts: 4310
Location: Mount Panorama, Australia
Registered: 21 Jul 2004
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 8:06 GMT

DennisS said:

On a full frame sensor camera the Tamron 10-17mm lens set at 12mm requires 4 shots around tilted up 5 degrees and 1 shot hand held straight down.

I think you mean Tokina 10-17mm not Tamron?

Regards, Smooth cool
www.omnipix.com.au
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Andrei2k

Posts: 5
Location: United States
Registered: 15 Mar 2014
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 13:57 GMT
Dennis thank you so much for the explanation, Im sorry when i said stretched I mean to achieve it via software setting not by hand but I think that clear it up. I think what has been happening is I havent gotten a perfect 180 vertically so I get wobbly top and bottom effect.

Do you know if the output (regular and cross) you describe can be achieved with PTGui and Kolor Pano?

Thank you,
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DennisS

Posts: 1787
Location: Los Anglels, United States
Registered: 1 Sep 2007
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 15:15 GMT

Smooth said:

I think you mean Tokina 10-17mm not Tamron?
That is what happens when you componse a long message in the middle of the night.

You are correct. Tokina. I do not own anything from Tamrom.

Andrei2k said:

Do you know if the output (regular and cross) you describe can be achieved with PTGui and Kolor Pano?

Pretty much all the stitchers can output a standard flat stitched image. I do not know which can do a cross. I actually pulled that image out with Pano2VR. It is sometimes used to fix stitching errors in post when your stitcher cannot handle your images.

PTGui is very popular here. I have not used any other program, so I cannot comment on them.

You need to get more than 180 vertical in your coverage. You need the overlap for proper blending. That is why you shoot a Zenith (if needed) and hand neld Nadir shot with your rig removed from the scene. If you have the Nadir adapter from Nodal Ninja, your camera can stay on your rig for the Nadir patch shot.

Dennis
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Andrei2k

Posts: 5
Location: United States
Registered: 15 Mar 2014
Re: Output a panoramic stretched to edges?
Posted: 22 Mar 2014 at 19:21 GMT
Thank again that helps, I guess I haven't done more than the 180 vertical which is probably the key.

I was looking at NN heads recently and was wondering which you would recommend for using with a Nadir adapter?

Thanks again,
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