fieldOfView | SPi-V devFACT OF LIFE:Straight lines become "squiggly" when viewing an equirectangular jpeg
Submitted by I_Bergmark on September 12, 2005 - 09:17.
Hi!
I think that the SPi-V engine is one of the best (if not THE best) panorama viewers for VR content.
I'm using engine version 1.3 beta6
I have noticed a slight problem though. When viewing an equirectangular jpeg, straight lines become randomly curved (squiggly). Not much, but enough to be noticable. I guess it might be the mathematical formula that's playing some tricks...
SPi-V with equirectangular jpeg: Squiggly lines
Quicktime or SPi-V with cubic jpeg: Straight lines
As mentioned above, the lines are straight if I use a cubic jpeg. The problem with this is that I get black lines in the seams when using a cubic jpeg with SPi-V.
Regards,
Ingemar Bergmark
My panoramas can be found here:
http://bergmark.com/vr_panorama01.htm
Squiggly lines; Update
I have a friend who is a Shockwave expert.
He explained to me that the SPi-V engine uses the Sphere Model to map the input images, which can cause this problem.
The problem is a tradeoff in performance with the Sphere model. It would take too much processing to make the image perfect.
He also took one of my images and created a Shockwave movie using the
Plan Model instead. With the Plan model all lines become straight.
I guess that when the input is an equirectangular jpeg SPi-V uses the Sphere Model, and when the input is Cube faces it uses the Plan Model.
The problem with Cube-faces is that I get black lines in the seams....
Thanks (and black seams?)
Thanks for posting the answer to your own question here. Its helpful for other people with the same problem.
Your friend is totally right. The only 'correction' I'ld make to your answer is I'ld use the term 'cube model' instead of 'plan model'.
There is an undocumented feature in the SPi-V XML that will let you set the sphere precission yourself, thus allowing you to make your own tradeoff between performance and quality. But since it is undocumented, I'll have to look it up in the code myself (*shame* :~|)
I see you are using the 1.3 beta viewer, and you say you are seeing black lines if you use cubic projection. Hmm... I hoped I had fixed that problem once and for all... Could you (1) post a link to a cubic panorama you use, and (2) tell me what type of graphics card you use in the machine that showed the black lines?
Black seams; sample
Here's a link to a panorama that's using cube-faces.
KBS Drama Movie Set - Observatory
The Black Seams have drastically been improved with the version 1.3 betas, but I'm still getting flickering black pixels in the seams as you can see in the example pictures below.
Sample 1
Sample 2
I've tested this on both PCs I own, and both show the same problem...
1) Sony VAIO with an ATI Mobility Radeon 7500C
2) No-brand PC with an ASUS V7100Pro (uses NVidia GeForce2 MX400)
Not black...
I see... You see some seams in the top (and bottom?) faces that are typically not black, and a black shimmering pixel here and there, right?
I'll see what I can do about that.
'do
Not black; clarification
Yes, shimmering black pixels is what I can see in the seams (both top and bottom).
But just to clarify one thing;
The light blue lines you see in my examples above were put there by me just to guide you to the black pixels.
Sorry for any confusion there...
shimmering black pixels only...
That is good news.
Squiggly lines with equirectangular images?
Hi Aldo,
I've searched the forum, but don't see a final answer to this question of squiggly lines when using equirectangular images. You mentioned an undocumented feature to improve precision. Were you able to find/document it? (The Immervision java viewer has the same problem with equirectangular images, but increasing the precision variable fixes it.)
I would use cubic images, but I've started to like JATC - Just Another Tour Creator, and it doesn't support cubic images. Are there any other GUI's for creating multi-node tours with Spi-V?
Thanks,
Craig Taylor