Camera in Houdini, is there an "auto vertical tilt correction"?

Forums Technical Discussion Camera in Houdini, is there an "auto vertical tilt correction"?

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iskan: Member; 18 posts; Joined: Aug. 2019; Offline

Sept. 15, 2019 11:36 a.m.

I work at Houdini, Redshift.
The question is, in 3Ds Max there is a checkmark in the “auto vertical tilt correction” camera, is there a similar one in Houdini?

Edited by iskan - Sept. 16, 2019 09:32:46

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Midphase: Member; 833 posts; Joined: Jan. 2018; Offline

Sept. 15, 2019 12:30 p.m.

Can you describe what it does?

>>Kays
For my Houdini tutorials and more visit:
https://www.youtube.com/c/RightBrainedTutorials [www.youtube.com]


iskan: Member; 18 posts; Joined: Aug. 2019; Offline

Sept. 15, 2019 12:47 p.m.

Midphase
Can you describe what it does?

Attachments:
5a184e7635a1d_VerticalTiltCorrection.jpg.9a5e7c98039876ec9d61d481e905391a.jpg (507.0 KB)
GUID-033EADA5-9CC8-4353-892B-A327BE6DCD1D.png (374.5 KB)
Безымянный.png (155.1 KB)


bonsak: Member; 459 posts; Joined: Oct. 2011; Offline

Sept. 15, 2019 1:49 p.m.

On the camera parameter View tab, try adjusting Screen Window X/Y's y parm, and then adjust the cameras Y Transform to frame the view. Its basically the same but not as straight forward as the Max button

-b

http://www.racecar.no [www.racecar.no]


iskan: Member; 18 posts; Joined: Aug. 2019; Offline

Sept. 15, 2019 2:34 p.m.

bonsak
On the camera parameter View tab, try adjusting Screen Window X/Y's y parm, and then adjust the cameras Y Transform to frame the view. Its basically the same but not as straight forward as the Max button

-b

t makes no sense to customize Screen Window X / Y's. Can you show where to configure “and then adjust the cameras Y Transform to frame the view”?

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Безымянный2.png (403.0 KB)


bonsak: Member; 459 posts; Joined: Oct. 2011; Offline

Sept. 16, 2019 2:23 a.m.

Here you go.

-b

Attachments:
psudo_pc_cam.hip (203.9 KB)

http://www.racecar.no [www.racecar.no]


iskan: Member; 18 posts; Joined: Aug. 2019; Offline

Sept. 16, 2019 3:45 a.m.

bonsak
Here you go.

-b

how did you do this?

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Безымянный3.png (737.7 KB)


anon_user_37409885: Member; 4189 posts; Joined: June 2012; Offline

Sept. 16, 2019 3:47 a.m.

To get the frustum, RMB on the camera and select Frustum Handle


iskan: Member; 18 posts; Joined: Aug. 2019; Offline

Sept. 16, 2019 4:10 a.m.

bonsak
Here you go.

-b

Sorry, but your method does not work, in some special cases it may be, but something else is needed in architectural animation.


doctorbob: Member; 30 posts; Joined:; Offline

Sept. 16, 2019 7:55 p.m.

if i had to guess, it looks like it's actually skewing/shearing the camera matrix in one axis. so the short answer is that no, houdini can't do that out of the box. it would be possible to do it in a mantra lens shader, i imagine. but nothing you could see in the viewport.

max is full of special archviz stuff like that, which other packages don't have equivalents for.

cheers,
chrisg


julca: Member; 219 posts; Joined: Oct. 2015; Offline

Sept. 17, 2019 12:43 p.m.

iskan
bonsak
Here you go.

-b
Sorry, but your method does not work, in some special cases it may be, but something else is needed in architectural animation.

Hello,

I'm curious, isn't there all options for what you want actually ?
Can you explain a bit more please ?

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cube.jpg (14.6 KB)


Midphase: Member; 833 posts; Joined: Jan. 2018; Offline

Sept. 17, 2019 1:10 p.m.

It's basically the CG equivalent of this technique:

https://www.canon.com.hk/en/club/article/itemDetail.do?itemId=10338 [www.canon.com.hk]

>>Kays
For my Houdini tutorials and more visit:
https://www.youtube.com/c/RightBrainedTutorials [www.youtube.com]


jsmack: Member; 8046 posts; Joined: Sept. 2011; Offline

Sept. 17, 2019 3:08 p.m.

You can calculate the shift amount from the tangent of the tilt angle and the ratio of the aperture to focal length. The y shift has to also be multiplied by the aspect ratio.

The hard part of automating this with a rig is figuring out what a ‘tilt’ is, and removing it from the transform.


julca: Member; 219 posts; Joined: Oct. 2015; Offline

Sept. 18, 2019 1:03 p.m.

Midphase
It's basically the CG equivalent of this technique:

https://www.canon.com.hk/en/club/article/itemDetail.do?itemId=10338 [www.canon.com.hk]

Thank you for the detail !
Even if it's very easy to set it manually (set camera rotation X to 0 and adjust the “screen windows” Y), an automatic function would be cool.


Gagui: Member; 56 posts; Joined: May 2017; Offline

Jan. 7, 2022 6:24 a.m.

Yes! I agree. We need an automatic function that tilt and shift the lens to adjust to camera target. It's very important for architectural visualization and motion graphics.
I know that vray has an option to add this property to a camera via vray physical camera properties but it's visible only in the render not in the viewport so it's difficult to work that way.


protozoan: Member; 1720 posts; Joined: March 2009; Offline

Jan. 7, 2022 7:06 a.m.

It's available in Houdini 19 (possible even as early as 18.5), it's called "physical lens" in Solaris, and does a couple of interesting things, including tilt/shift.

In your LOPnet, put down a material library, add a physicallens VOP and reference that as the lens shader VOP from your camera (it's under the "karma" tab).

Martin Winkler
money man at Alarmstart Germany


Gagui: Member; 56 posts; Joined: May 2017; Offline

Jan. 7, 2022 7:57 a.m.

Are lens shaders visible in standar opengl viewport?

I've tried what you said but I can't see any effect on the viewport neither vray render.
Perhaps this shader is only compatible with karma render...


brianrwalters: Member; 1 posts; Joined: Aug. 2020; Offline

April 22, 2022 1:28 p.m.

I tried, and no, it's still not visible in the 3d viewport. This makes it really hard to work with. I sure hope sidefx can add support.

To my simple eyes, Vertical Aperture Offset (for USD, winx/winy for an obj camera) look aboooout the same as a vertical lens shift. (I'm able to keep vertical lines vertical). Can someone calrify what's the difference between the two?


R_Stewart: Member; 56 posts; Joined: March 2022; Offline

May 2, 2022 7:57 p.m.

Hello all, I'd say that this is a much needed feature in all 3d packages. I personally need to render things at very specific perspectives with all verticals straight so that the content fits on a big screen and still feels like the same perspective as the viewer.

See what I do here. I move the camera down to eye level, keep all rotation at zero and extend the view to get all the pixels I need. Then render a patch. Seems dodgy but it does the trick for me

I can't actually find the aperture offset that you are talking about. Can you point me in the right direction so I can try that?

Edited by R_Stewart - May 2, 2022 20:00:52

Attachments:
StraightVerticals.JPG (295.2 KB)


jsmack: Member; 8046 posts; Joined: Sept. 2011; Offline

May 2, 2022 8:24 p.m.

brianrwalters
I tried, and no, it's still not visible in the 3d viewport. This makes it really hard to work with. I sure hope sidefx can add support.

I don't see lens shaders ever being supported in a gl view, unless the gl view uses raytracing extensions. it's just not possible to control the imaging with a lens shader when rendering with rasterization.

brianrwalters
To my simple eyes, Vertical Aperture Offset (for USD, winx/winy for an obj camera) look aboooout the same as a vertical lens shift. (I'm able to keep vertical lines vertical). Can someone calrify what's the difference between the two?

Vertical/Horizontal aperture offset is what I would use. The lens shader is overkill for a simple 2D transformation.

R_Stewart
See what I do here. I move the camera down to eye level, keep all rotation at zero and extend the view to get all the pixels I need. Then render a patch. Seems dodgy but it does the trick for me

Use the window offset to shift the image. You don't need to extend the image. Window offset is on the View tab of the camera object.

R_Stewart
I can't actually find the aperture offset that you are talking about. Can you point me in the right direction so I can try that?

Aperture offset is the USD term for window offset, and is only used in Solaris/LOPs.

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