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Subject: Distorting sky photographs for mapping onto spheres?


Angelouscuitry ( ) posted Sun, 25 March 2007 at 6:05 PM · edited Fri, 19 July 2024 at 5:17 AM

In a thread, that has rolled into a discussion about Sky Domes, Ajax has offered an awsome free poser sky dome!  I would love to know where his sky domes' texture map got it's distortion?  

My guess was that this was the Distort filter, but Polar coordinates was my best gues.  His answer is that E-On Vue does that it, but I'm also interested in distorting plain photographs.

If you look at my post, dated Sun, Mar 25, 2007 4:25 am(A chrome/blue Angel with a pink squigly,) you can see what I'm getting at.

Could anybody explain what Vue is doing?


prixat ( ) posted Mon, 26 March 2007 at 3:14 PM

Hi Lou That does look like 'polar coords.' distortion. What results do you get when you make your map?

regards
prixat


Angelouscuitry ( ) posted Mon, 26 March 2007 at 5:15 PM

Hi Prixat,

There are two ways to apply that filter.  Just using either, once, makes for huge distortions.

I've two liks to try:

HDR Shop

and

A Photoshop Tutorial(Using Poar Coordinates)

I'll try both, soon, and be back with results.


karosnikov ( ) posted Tue, 27 March 2007 at 1:42 PM

file_373132.jpg

hmm.. try to paint a simple grid and distort it, Vue is probaly re-distorting almost the opposite way, since you have Vue it might become more aparent seeing what happens to both a distorted and a non distorted image.


bushi ( ) posted Tue, 27 March 2007 at 5:10 PM

file_373159.jpg

This is a panorama exported from Vue6 Esprit and applied to a skydome sphere that I built in Silo. I wanted the sphere to use cylindrical UV mapping so I used a mapped cylinder and distorted it into a sphere in Silo. The next message has examples of the panoramas that can be exported from Vue.


bushi ( ) posted Tue, 27 March 2007 at 5:13 PM

file_373160.jpg

The top panorama is the one used for the image in the previous message. The bottom image show the inverted "U" shapes that Angel noticed in the previously posted thread. One more pic in the next message.


bushi ( ) posted Tue, 27 March 2007 at 5:20 PM · edited Tue, 27 March 2007 at 5:24 PM

file_373161.jpg

I also tried using the panorama as a material in the hi-res Poser ball prop. I had to reverse the normals to get the image to show on the inside of the sphere. Positioning was done with the sphere set to display in wire frame mode. It was also necessary to set the texture strength to 1.1 to keep the clouds from looking muddy. There is a demo version of Vue6 Esprit on the E-on Software site. You can't render images larger then 640X480 but I think that would be enough resolution to at least do some testing. Almost forgot to add that at the top and bottom of the spheres the panorama doesn't close together properly so looks odd. For most applications this shouldn't be a problem.


Angelouscuitry ( ) posted Thu, 29 March 2007 at 2:19 PM

I have Spherical Mapping corrector, but it uses a much different formulae.  It onoly really distorts the top and bottom of an image.  If you look at the thread, I linked to in my first post, you'll see that the distortions go stright through the hieght of the map?

I've got to HDR SHop V1., and see that the Latitude/Longitude image, at  the HDR Shop's Panoramica Conversion Tutorial page,  is about what I'm aiming at.  I do'nt understand how to replicate that with the program?

Here are the steps I tried:

1.)  I chose an image to use, and clicked File > Open, to load it into HDR SHop V.1.(Leaving the Camera ResponseCurve alone.)  It does'nt quite look like the whole Panorama of the image loaded, does it?

2.)  I then navigated to the Panoramic Transformation dialog, illustrated in the tutorial.

3.)  But now I'm stuck on what Source and Destination Formats to use?


Prikshatk ( ) posted Fri, 30 March 2007 at 10:39 AM

file_373417.jpg

Hi Lou I don't think the HDRshop conversion is going to work because it assumes your working from a distorted image to start with.

The photoshop 'distort' tutorial gives quite good results, see attached.

regards
pk
www.planit3d.com


Angelouscuitry ( ) posted Fri, 30 March 2007 at 7:04 PM

Thanks prixat!

I've writen the author of HDR, and am hoping for a reply.

How did you perform step 3?  It says to use the Eliptical marque tool to make a perfectly circular selection, around the eliptical distortion of step 2.  So, did you select the height or the length of the distortion? I think it would be the height(Given the constraint) but then it says something about the top edge? 

I looked for an e-mail, to write this author also, but maxon computer looks like a pretty big company, and doubt their main e-mail(info_us@maxon.net) would be pertinant?


Prikshatk ( ) posted Mon, 02 April 2007 at 6:07 AM

Lou
I didn't bother with a circular mask, just followed roughly the same size as the ellipse the distort produced. I reduced the feathering to avoid picking up any straight edges.

(As you can see I also simplified it by just doing the clouds above the horizon.)

regards
pk
www.planit3d.com


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