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Re: Test

Etienne Monneret (Perso)
 

Le 26/04/2021 à 21:02, robert mcafee via groups.io a écrit :
Apologies, just a test to see if still subscribed
Have a look at this page to see if some mails sent by Groups.IO are refused by your mail box:

https://groups.io/account?page=bounces

;-)


5 Left Hands In A Box

 

I prefer to look at real 3D, rather than flat images that have to be viewed at specific angles to look like real 3D: 
 
"hand" (https://skfb.ly/6EIoV) by kevinruiz.
 
 


Looking At The Real Thing

 

Tell me something, kids...
Why struggle looking at 3D on flat image planes, when we can look at the real thing?
 
"hand" (https://skfb.ly/6EIoV) by kevinruiz.


 
 


Re: 3D Pop-Left (or Right)

Etienne Monneret (Perso)
 

Le 26/04/2021 à 12:22, robert mcafee via groups.io a écrit :
Barry Rothstein has published several books of phantom rams which provide information on making your own. He also has information on his websites. Barry did a live tutorial at the NYSA stereo club Zoom meeting this past Saturday. He showed his process with photoshop and using StereoPhoto Maker.
I found his tutorial on this web site:

http://3ddigitalphoto.com/

Direct link to the document:

http://3ddigitalphoto.com/phantograms.pdf

;-)


Re: 3D Pop-Left (or Right)

robert mcafee
 

Barry Rothstein has published several books of phantom rams which provide information on making your own. He also has information on his websites. Barry did a live tutorial at the NYSA stereo club Zoom meeting this past Saturday. He showed his process with photoshop and using StereoPhoto Maker. 




On Monday, April 26, 2021, 1:35 AM, Etienne Monneret (Perso) <ab3d@...> wrote:

Le 25/04/2021 à 23:24, Antonio F.G. via groups.io a écrit :
> All this sounds very interesting. For Stmani3 I have to think if I
> could set a condition of zero-disparity for a set of points. Perhaps
> only three points to define a plane.

The best is to shoot the scene with a reference plan shape somewhere
(ideally a square, as you said, you only need 3 points), this shape
being horizontal on the reference (ground) level, and then to change
each shot view with a perspective transformation to get back exactly the
original shape with zero parallax. So, in your process, it would be nice
to load 3 images: left, right, and original shape alone. Of course, it
would often be nice to be able to remove the shape on the final stereo,
or use a shape that could be nicely integrated in the scene (like my
chess board).








Re: 3D Pop-Left (or Right)

Etienne Monneret (Perso)
 

Le 25/04/2021 à 23:24, Antonio F.G. via groups.io a écrit :
All this sounds very interesting. For Stmani3 I have to think if I could set a condition of zero-disparity for a set of points. Perhaps only three points to define a plane.
The best is to shoot the scene with a reference plan shape somewhere (ideally a square, as you said, you only need 3 points), this shape being horizontal on the reference (ground) level, and then to change each shot view with a perspective transformation to get back exactly the original shape with zero parallax. So, in your process, it would be nice to load 3 images: left, right, and original shape alone. Of course, it would often be nice to be able to remove the shape on the final stereo, or use a shape that could be nicely integrated in the scene (like my chess board).


Re: 5-Sided Pop-Out In A Box

 

Hey, kids, I'm gonna pass the torch on this one. I think the contact cement I used in the box is getting me high.
I better go back to the Medieval Fantasy Book before I have to check in to rehab.
Good luck!


Re: 5-Sided Pop-Out In A Box

 

I am able to check this with Blender VR, and it looks very promising. Notice the spacer (foam core) behind the image on the back side of the box where a normal perspective 3D image (anaglyph) is placed.


Re: 3D Pop-Left (or Right)

Antonio F.G.
 

It sounds correct: the horizontal perspective induces vertical disparity errors but they are cancelled when viewed from an angle exactly equal to that of the perspective.

That means the pop-right, pop-left phantograms can indeed work, but may be critical in regard to the viewer position. If the viewer looks from a non optimal angle, then vertical disparity would appear.

In contrast I think pop-up, pop-down phantograms should not produce any vertical disparity regardless the angle they are viewed from. By modifying the angle they will show funny perspective effects, but at least no head-aches:-).

All this sounds very interesting. For Stmani3 I have to think if I could set a condition of zero-disparity for a set of points. Perhaps only three points to define a plane.

Regards
    Antonio


5-Sided Pop-Out In A Box

 

I've placed my 5-sided 3D pop-out idea inside a 2'x2' cubic box, and I'm ready for 3D images.


Re: 3D Pop-Outs At The Golf Course Aren't Cubic

 

On Sat, Apr 24, 2021 at 11:04 PM, Etienne Monneret (Perso) wrote:
Why ?
I'm still working this out.
Actually, I will be able to place a cubic box around the whole thing, after all.
Stay tuned!


Re: 3D Pop-Left (or Right)

JackDesBwa|3D
 

Why "alignment is not perfect"? It seems quite good for me.

It is not perfect in the sense that it is not computed as the exact projection, that could be awaited from a modeled scene.

I used the perspective tool of the Gimp to go from the rendered image to the phantogram image, by placing the grid manually over the square.
This results in small inaccuracies, such as the plane not being exactly at zero parallax for example. But the difference with ideal is indeed small, except perhaps in terms of resolution.

JackDesBwa


Re: 3D Pop-Left (or Right)

Etienne Monneret (Perso)
 

Le 24/04/2021 à 23:18, JackDesBwa|3D a écrit :
Then I imagined a head popping from a hole in a wall, exported a 3d image and transformed it quickly (alignment is not perfect) into a phantogram.
Why "alignment is not perfect"? It seems quite good for me. Small vertical disparities in the larger parallax are normal (see my other message).


Re: 3D Pop-Outs At The Golf Course Aren't Cubic

Etienne Monneret (Perso)
 

Le 25/04/2021 à 05:35, Roger Maddy a écrit :
I looked at my 3D pop-outs (straight, up, down, left and right) at the golf course, and realized you can't make them with a perfectly cubic box:
Why ?


Re: 3D Pop-Left (or Right)

Etienne Monneret (Perso)
 

Le 25/04/2021 à 00:08, Antonio F.G. via groups.io a écrit :
But if it is stereo there are other difficulties. Most important, there should not be vertical disparity. This is where I doubt that you can apply perspective transformation in any direction. On my view only the vertical perspective does not worsen the stereo alignment (vertical disparity).

Phantogram does not create stereo disparity problem.

When you do the projection, of course the result, seen as a direct orthogonal viewing, may show deformations like the well-known stereo keystone problem, especially if this is a vertical phantogram.

In the Jack's example, it can already be seen on the place where there is the larger parallax:

BUT, the phantogram must not be seen with a perpendicular viewing, like an ordinary stereo. It must be seen with a 45° angle. In this way, the perspective of the phantogram itself do a reverse disparity correction.

By construction, your eyes always see exactly the same thing at 45° on the phantogram, that what was seen at perpendicularly on the original stereo before the phantogram projection.

It's understandable on my drawing: point to point in the image, each eye see EXACTLY the same thing. If you do not have bad disparity on the original image (red plan), you won't see any disparity in the projected image (blue plan), even if this projected image shows disparities when seen perpendicularly (it's not intended to be seen perpendicularly).



3D Pop-Outs At The Golf Course Aren't Cubic

 

I looked at my 3D pop-outs (straight, up, down, left and right) at the golf course, and realized you can't make them with a perfectly cubic box: 


Re: 3D Pop-Left (or Right)

Antonio F.G.
 

Granted, the phantogram the transformation may be in any direction.
But if it is stereo there are other difficulties. Most important, there should not be vertical disparity. This is where I doubt that you can apply perspective transformation in any direction. On my view only the vertical perspective does not worsen the stereo alignment (vertical disparity).

Regards
     Antonio


Re: 3D Pop-Left (or Right)

JackDesBwa|3D
 

I agree that it should be possible, and wanted to see how it looks like in reality.

Then I imagined a head popping from a hole in a wall, exported a 3d image and transformed it quickly (alignment is not perfect) into a phantogram. The 3D scene does not look like I wanted, but the effect works.

I attached the test images if you want to see them. [parallel versions]
The image named 'scene' is the export from the modeling software, which also helps to see how it looks like with a regular camera.
The other image named 'result' is the phantogram to see from the side (image at 45° on your left, facing to your right).
view.png

It is not as pleasing to view as regular phantograms in my opinion, because turning the head down to view a figurine is quite natural, but in this case with the image on the left, I want to adjust my position to come back in front of it.

JackDesBwa


Re: 3D Pop-Outs With A Cardboard Box

 

Whoops. It has to be a perfectly cubic box, so be sure your box has perfectly square faces. Also, it helps if you cut off the top pieces.


Re: 3D Pop-Left (or Right)

Etienne Monneret (Perso)
 

Note that  the anamorphosis is not the same for left and right views: there is a small horizontal shift according to the stereo-base. The different perspective projections (from red plan to blue plan) should set the parallax to zero for the whole ground plan (reference square).

Le 24/04/2021 à 15:09, Etienne Monneret (Perso) a écrit :
There is no link between the stereo keystone problem and the phantogram transformation.

It's only a question of what should be print according to the viewing position, nothing more.

Common stereo are made to be viewed as the cameras shot them, thus your viewing line must be perpendicular to the plan of the picture. If you look at it looking down at a 45°, to see what the cameras was shooting, you need to keep it perpendicular (red line).

Now, if you want to look at it put horizontally on a table, to be able to see what the camera was shooting, you need to make a perspective projection (blue line). This is what is doing the anamorphosis (reversing the original perspective effect).

You can do this projection in any kind of direction!



Le 24/04/2021 à 14:56, Antonio F.G. via groups.io a écrit :

[Edited Message Follows]

I am just starting to understand this phantogram trick as a pop-up effect (or pop-down if I could place the image in the ceiling:-). In both cases a vertical perspective (vertical keystone) could be applied. I have worked a little with perspective alignment, and I can say that vertical perspective does not worsen the stereo alignment, i.e. you can modify the vertical keystone of any aligned stereo pair at will, and be sure the image while distorted will still keep aligned.

But you are talking of pop-right, pop-left. This is a very different thing, because horizontal perspective (h. keystone) does affect the stereo alignment. If you apply an H. perspective to an aligned pair you will worsen the alignment. In your example of the horizontal cone, what if you had not cropped out all the background of the original images?. I guess it would be un-viewable because of vertical disparity in the background. The image that shows the cone with a 45˚ h. perspective is viewable only because there is no background.

Regards
    Antonio


On Fri, Apr 23, 2021 at 07:45 PM, Roger Maddy wrote:
So... a 3D pop-left (or right) is working without the neck-breaking agony of creating and viewing a 3D pop-down.
The 3D camera angle is 45 degrees (left or right), and you have to view them with that same angle.
 
Hope this helps.

Parallel view.



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