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Thursday, March 21st 2019, 2:32pm

Hotspots positions relations between monoscopic and stereoscopic modes in same panos

Hello everyone

Again I post in the beginners section because what I want is probably obvious for advanced users.

For stereo panos we can put hotspots at different depth levels, so they appear at the wanted depth in the 3D space. It means that when in stereoscopic/3D mode any hotspot will have a particular relative position in the left view, and another relative position in the right view, so that it appears in correct relative depth/distance when we view in stereo. Also any stereo pano can be rendered in monoscopic/2D mode, in that case I think the default view used is the left one. The default hotspots are shared between mono and stereo modes of the panos, so logically in monoscopic mode the hotspots positions should be the same as the ones of the same hotspots in the le left views of the stereoscopic mode. But It seems it is not the case. I tested with several stereo panos and it seems that it is reverted, so that the position of any hotspot in the monoscopic mode is the same as the position in the right view of the stereoscopic mode. This is not very visible but it can be a problem in some cases, especially when hotspots are near some objets that are not at the same depth level in 3D space, because it will create some unwanted superpositions, either in 2D or 3D modes. Maybe it is a bug in krpano, because for me it seems the situation should be logically reverted. Maybe it is possible to overcome this by setting the 2D mode with the right eye views but I didn't see yet how to do that.

Also I think it is possible in krpano to use 3 views for each stereo pano, one for left eye, one for right eye, and a "middle view", used to render the monoscopic/2D mode. Of course it depends on the stereoscopic acquisition method used, in some cases you only have the left and right views, but you can also have "middle" view with "angular stereo" methods. I have many panos rendered with this method (with left-middle-right views), and even with multiple stereo bases distances for left and right. So in the case of 3 views for each pano, the hotspot positions of the monoscopic/2D mode should be set at the "middle" of the positions in the left and right views of the stereoscopic/3D mode. Are all these things already easily possible to set in krpano ?

I have some others questions/ideas about stereo panos but I will keep them for other threads.

Regards

2

Wednesday, March 27th 2019, 6:59pm

Hi,

not an easy to explain topic, but I will 'try'...
(btw - there is no bug or something like that)

For stereo panos we can put hotspots at different depth levels, so they appear at the wanted depth in the 3D space. It means that when in stereoscopic/3D mode any hotspot will have a particular relative position in the left view, and another relative position in the right view, so that it appears in correct relative depth/distance when we view in stereo.
First one important note - 'stereo pano's are mainly a 'hack' - they work because our brain only needs different the left/right distances to feel depth. But in 'reality' (or technically) they are not correct a 3D- or stereo-image. Each vertical line in stereo-pano can be from an different viewpoint! (think about how stereo-panos are created/stitched).

You could see that when trying to make a hotspot matching some content in the stereo-pano (e.g. an image should cover a TV) - the hotspot will move slightly differently than the pano image when looking around. Regardless what depth will be used, in some viewpoints it will always be wrong. And that's because the stereo-pano image itself is stitched together from of several different viewpoints.

Also any stereo pano can be rendered in monoscopic/2D mode, in that case I think the default view used is the left one.
No, in stereo-rendering there is a distance/offset between the left- and right rendering-cameras (viewpoints) - can be also called 'eye-separation'. But that distance applies only to the hotspots, because the pano itself is a 'pano' and that way always infinity away.

The 'best' way for integrating hotspots into a stereo-pano image would be using prepared stereo-hotspot images - that means the hotspot graphic would be need to individually stitched/drawn into the left and right pano images and then cropped out from there for usage as hotspot (with exactly the same cropping values for left and right).

For using such created hotspots there is stereo setting:
https://krpano.com/docu/xml/#hotspot.stereo

Best regards,
Klaus

3

Wednesday, March 27th 2019, 11:34pm

Hi Klaus, thank you very much for this interesting reply *tongue*

I just witnessed what you said about " the hotspot will move slightly differently than the pano image when looking around ". In stereo/VR mode you can see that by closing one eye and looking at one hotspot while moving around. In monoscopic/2D mode there is no such drifting of hotspots. Is it an intended behavior for stereo ? Isn't it possible to stick hotspots to their backgrounds on each side ? Actually it would be like placing any stereo hotspot by hand on the left then on the right panos and sticking them there.

As for the monoscopic/2D mode I was speaking about the fact that for stereo panos, there are the image files for left and right panos separated in panos folder, and in regular 2D mode the left image files are used by default. And to me it seems that when you switch between mono/stereo modes without moving pano view, you can see that hotspots jump horizontaly relatively to the background, very much for left panos independently, very little for right ones. So there is an asymmetry. It led me to think that hotspots positions of right panos where used in mono/2D mode but on top of felt images. But I am probably confused with how it works.

I just saw also the possibility of prepared stereo-hotspot with the stereo parameter. I didn't know that before, this is very interesting, it brings the possibility to have hotspots with parallax discrepancy inside them so they can render in stereo themselves (not stay flat).
Is it also possible to have them both stereo and animated (crop animation) ? Because it should do animation crop "insde" the stereo crop. I just tried to put both arguments ('stereo' and 'do_crop_animation') in one hotspot but it just disappeared altogether.

I am also interested to know how to change the images used to compose the regular/2D modes in global stereo panos. As I said above it is by default the left side images. I would like to be abble to use right side images instead. Or even images different than left and right. Because for many stereo panos I generate actually 3 points of view, one left, one middle and one right. It is possible with circular/angular shooting, with just one camera rotating or with devices like Kandao Obsidian, Insta 360 etc. So in those cases I want to use the middle renders to display in 2d modes, because they have a sligthly better resolutions than left and right renders, due to the processing method. I think it was possible in an old verion of krpano but I forgot how. How to do that now in the last version ?

I don't know how you handle all the stereo stuffs under the hood in krpano but I imagine it is quite complex, on top of the other features. I would like to understand all those thing better but it's a shame I am still a newbie in krpano universe... I feel there is a great output potential by mastering krpano, so I will improve for sure. I have a solid knowledge now in 360 stereo photography and krpano is the only tool that I know in my short term reach that I could use to create great VR virtual tours. So a great thank you for your work Klaus. I am awaiting the next krpano update impatiently *g* (and I hope to have improved a little before that).

Regards
Hoel