What, exactly, does the "lens shift" value do to the camera?

[manamana]

Being both an architect and photographer, I use shift lenses pretty regularly on actual camera. If you're curious about their functionality, see this link, and scroll down to "The Rising and Falling Front":

http://www.luminous-landscape.com/re...on_24_pc.shtml

What puzzles me is that the "lens shift" value in vray does not appear to function similarly. The "lens shift" value seems to have the effect of both tilting the camera down and then shifting up to replicate the original framing. This makes it very hard to marry shifted vray output with sketchup hidden line output in photoshop, not to mention making it difficult to work precisely with respect to perspective and distortion in the same way that I am accustomed to with my camera.

I was thinking it may be possible to work backwards if I knew what, exactly, that value was doing to the camera, and it's units, if it has any. Inches? mm? percent? Mathematically what is going on when one applies "lens shift" in Vray for sketchup?

[blitzer_26]

Re: What, exactly, does the "lens shift" value do to the camera?

It is a lens used to correct or enhance perspective, unless you leave lens shift at 0 your sketch up lines are gonna be a pain.
http://en.wikipedia.org/wiki/Perspective_control_lens

Recommend:
not using sketch up lines and going nuts with lens shift,or
not using lens shift and going nuts with sketch up lines,

If your model & render are done well there shouldn't be an need for the lines, if not look into TOON MATERIALS

[manamana]

Re: What, exactly, does the "lens shift" value do to the camera?

I hate to be rude, but I suspect you didn't even read my post. I'm well aware of what a real shift lens does (I own one), the problem is "lens shift" in Vray very obviously don't work in the same way. I want to better understand how it works so I can work precisely with it.

I dug through the chaosgroup forums and found several folks asking for the same info, none of whom ever got a reply.

[andybot_cg]

Re: What, exactly, does the "lens shift" value do to the camera?

Hi there,

Glad to see you posting about this. I'm a photographer too, and understand lens shift. I find it's kind of pointless to try and apply photographic principles beyond exposure and aperture to this software as it's all basically guesswork to make anything resemble what a real camera would do. I basically do anything more complex like lens shift as postprocess in photoshop where you have complete control. Just bump up the resolution of the render to account for the loss of pixels.

-Andy

[blitzer_26]

Re: What, exactly, does the "lens shift" value do to the camera?

I hate to be rude, but I suspect you didn't even read my post. I'm well aware of what a real shift lens does (I own one), the problem is "lens shift" in Vray very obviously don't work in the same way. I want to better understand how it works so I can work precisely with it.

I dug through the chaosgroup forums and found several folks asking for the same info, none of whom ever got a reply.

I suspect you didn't even read my post... Look into TOON Materials

[rspierenburg]

Re: What, exactly, does the "lens shift" value do to the camera?

I'm curious to know what toon material would have to do with lens shift as well.

[andybot_cg]

Re: What, exactly, does the "lens shift" value do to the camera?

Hehe, not the most cordial exchange... The post by blitzer_26 does actually respond to one of the issues brought up by the OP. The toon material allows for generating the hidden line effect to the same perspective that is not achievable through SU. One simple way would be to use the toon material as a global override material and generate a rendering of just the toon outline and use that as a photoshop layer over the regular rendering.

[blitzer_26]

Re: What, exactly, does the "lens shift" value do to the camera?

I'm curious to know what toon material would have to do with lens shift as well.

Hehe, not the most cordial exchange... The post by blitzer_26 does actually respond to one of the issues brought up by the OP. The toon material allows for generating the hidden line effect to the same perspective that is not achievable through SU. One simple way would be to use the toon material as a global override material and generate a rendering of just the toon outline and use that as a photoshop layer over the regular rendering.

Refreshing to see someone knows whats going on...

[thomthom]

Re: What, exactly, does the "lens shift" value do to the camera?

Hehe, not the most cordial exchange... The post by blitzer_26 does actually respond to one of the issues brought up by the OP. The toon material allows for generating the hidden line effect to the same perspective that is not achievable through SU. One simple way would be to use the toon material as a global override material and generate a rendering of just the toon outline and use that as a photoshop layer over the regular rendering.

Unfortunately the Tool material doesn't always generate the desired effect like the one you get from SU's line work. Often it skips many of the edges, it's more outlining the geometry.

[andybot_cg]

Re: What, exactly, does the "lens shift" value do to the camera?

Good point. It also does not render lines, only edges of faces. Personally, I use sketchy edges whenever I use a line overlay, and for that toon doesn't help.

[ValeroStudio]

Re: What, exactly, does the "lens shift" value do to the camera?

I always adjust my perspective in Photoshop using the Distort - Lens Correction filter on my final image to make the rendering look as if you used lens shifting. You can use this method with or without SU lines or toon materials or whatever you want. Until we can get Vr4SU to match a view in SU when 2pt perspective is turned on, it doesnt make sense wasting time with these settings IMO.