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Poser F.A.Q (Updated: 2016 Nov 29 4:50 pm)


 Subject: Magnifying Glass - How to strengthen or invert the effect?

monkeycloud opened this issue on Jan 21, 2013 · 66 posts

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  monkeycloud    ( ) ( posted at 2:38AM Mon, 21 January 2013 

Done some searching and trawling, but I've not found anything that quite explains this adequately for my poor Monday brain...

This is probably quite basic stuff, and I know I should experiment more... sorry... but I am hoping someone might already know the answer and give me some guidance :)

I'm trying to make the effect of looking through the reverse side of a magnifying glass.

I'm using the Refract Node at present... is this correct, for starters?

What settings do I need to increase / decrease / invert to get the effect I'm after?

Many thanks for any advice or guidance you can give here...

p.s. I am trying to combine this with reflection ultimately, to get a reasonable glass like appearance, with real reflections. But let's start with the basic refraction effect I guess? I clearly need to understand this some more, relative to Poser's Refract node etc...


  ashley9803    ( ) ( posted at 3:01AM Mon, 21 January 2013  · @4033197

Quote - I'm trying to make the effect of looking through the reverse side of a magnifying glass.

Looking through either side of a magnifying glass is exactly the same. They have no reverse side.


  monkeycloud    ( ) ( posted at 3:32AM Mon, 21 January 2013  · @4033199

Quote - > Quote - I'm trying to make the effect of looking through the reverse side of a magnifying glass.

Looking through either side of a magnifying glass is exactly the same. They have no reverse side.

He he :-) Doh! What am I thinking of then... something else clearly. Just another lens of some sort I guess!

Don't have a magnifying glass in the house, or else I might have realised that... ha ha!

Okay... that makes things simpler then!

Well, in that case, any pointers on how I would just increase the magnification effect?

Many thanks


  monkeycloud    ( ) ( posted at 4:23AM Mon, 21 January 2013  · @4033206

Hmmm... I mentioned I was suffering from Monday-itis didn't I...

I guess to make the magnification stronger, it's just the geometry of my convex lens I need to alter... per the real world?

Guess I can make a morph for that...

;-)


  EnglishBob    ( ) ( posted at 5:34AM Mon, 21 January 2013  · @4033221

Attached Link: http://en.wikipedia.org/wiki/Lens_(optics)

Unlike real-world lensmakers, you also have the option of increasing refractive index without limit. ;)


  monkeycloud    ( ) ( posted at 5:42AM Mon, 21 January 2013  · @4033222

Ah, many thanks EnglishBob :)

I wondered if just upping the IOR would do it... thought that had to be the setting I needed to change... but it was the maths of that I was unsure about really I guess...

...e.g. if I had to increase the IOR, or invert it, or what.

I've made a nice morph to increase the thickness (or rather z-depth diameter) of the magnifying glass prop lens now too...

...so I will play around combining that "increase magnification" morph, with increasing the IOR.

Originally, I'd woken up with the notion that the lens of a magnifying glass was convex on one side and concave on the other! Which, of course, makes no sense, I don't think, in the real world.

It is Monday... this sort of thing seems to happen to my brain, on a Monday... ;)


  EnglishBob    ( ) ( posted at 6:29AM Mon, 21 January 2013  · @4033233

To a first approximation, it's the radius of curvature which determines the strength of the lens, not its thickness - and Poser won't render a particularly accurate simulation anyway. If you do want to make a variable focal length, simply scaling the lens thickness would work fine since that will also increase the curvature / reduce the effective radius.

A lens with one convex and one concave face is called a meniscus lens - and it can still magnify or reduce depending on the relative radii. Contact lenses always have the inner face concave so as to fit the curvature of the cornea. Guess who's father used to be an optician? :)  


  monkeycloud    ( ) ( posted at 6:38AM Mon, 21 January 2013  · @4033237

Thanks... yes, actually it was the radius of curvature I increased in the morph, er, I think ;)

Well... I made the lens more, er, "spherical"... if that's the best way to put it... in Hexagon and loaded that back in as a morph.

A meniscus lens... contact lens... yes, of course :)

Anyway... as Ashley9803 pointed out, my magnifying glass should only magnify... not de-magnify, whichever side of the lens I look though, he he...


  EnglishBob    ( ) ( posted at 6:48AM Mon, 21 January 2013  · @4033241

Quote - ...my magnifying glass should only magnify... not de-magnify, whichever side of the lens I look though, he he...

Indeed it will.

Practical magnifying glasses are often made with assymetrical curvatures, which I seem to remember is something to do with reducing chromatic aberration. No need to worry about that, though; Firefly is nowhere near an accurate enough light simulator to have that problem.

On the other hand... Your magnifying glass effect might be enhanced if there was some visible aberration. I have no idea how to achieve that in the renderer, though, or even if it is possible at all; I suspect not. Postwork may be required. ;)  

 

 


  monkeycloud    ( ) ( posted at 6:57AM Mon, 21 January 2013  · @4033242

Yes indeed, some postwork may be resorted to ;)


  mysticeagle    ( ) ( posted at 10:57AM Mon, 21 January 2013  · @4033329

dunno if I'm losing me marbles, but remember when you were at school doing pencil drawings of a bottle for art class, there was always that little reflection bubble i used to call it that the teacher insisted you got into the drawing to simulate a real world reflection, maybe incorporating something like that as a layer might have the desired effect.

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  monkeycloud    ( ) ( posted at 11:03AM Mon, 21 January 2013  · @4033332

Ha ha... yes, I think I know exactly what you mean Mystic ;)

I used to always add something like that when I hand drew pen and ink comic strips as a kid...


  aRtBee    ( ) ( posted at 11:39AM Mon, 21 January 2013  · @4033350

I did one, a very long time ago, in Bryce. Pick the Looking Glass image from http://www.main.artbeeweb.nl/?p=3990 

Each one was made of two slices of a ball, glued together. Ball was made of simple glass, index 1.5 or so.

Each looking glass has a focal length. If you're inside that range, the image turns upside down. So if you set each magnifying glass withing the focal range of the next one, you'll get a series of flipping images. In the first, you can see the second upside down which shows the third one straight up. The renderer must do that automatically.

But do note that you have to crank up the max amount of ray bounces in the render settings, otherwise the inner ones will turn black. Each glass adds four bounces (ingoing, two halfay and outgoing) so this image required at least 20.

have fun.

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  monkeycloud    ( ) ( posted at 11:58AM Mon, 21 January 2013  · @4033362

Ah... wait... the flipped / compressed image is actually exactly what I was originally talking about / expecting to get...

...well, I'd forgotten the flipped part...

http://www.warren-wilson.edu/~physics/PhysPhotOfWeek/2007PPOW/20071130LensPPOW/index.html

...and this is exactly what I am now getting.

The magnifying glass prop in my scene is a bit of a distance from the camera.

It all makes much more sense now :)


  shvrdavid    ( ) ( posted at 12:30PM Mon, 21 January 2013  · @4033375

If I remember right, Poser can do a magnifying glass or glasses with 5 or 6 raytrace bounces. You have to model both sides of the glass to get it to work.

I think BB did a writeup on it as well, not sure if it was here or at DNA thou.

https://forum.smithmicro.com


  Rance01    ( ) ( posted at 1:02PM Mon, 21 January 2013 · edited on 1:07PM Mon, 21 January 2013 · @4033390


Refraction Index of Refraction increases the effect.  I think the venerable BagginsBill had a thread here somewhere.  I do have the material used to make this picture (had to re-trace the thing using saved stuff in my libraries.

Is this what you are looking for?

Best Wishes,

Rªnce


  Rance01    ( ) ( posted at 1:11PM Mon, 21 January 2013  · @4033393

I take no credit for the material used here.  As I said, I think I copied notes posted by BagginsBill.  Most of the tricky stuff I do comes from that source.  I do not have a link to the original thread, but I can post a screen shot here of the settings used, or upload the MAT file and post a link here to it.

Maybe someone has a link to the thread.

Be Well,
Rªnce


  monkeycloud    ( ) ( posted at 3:11PM Mon, 21 January 2013  · @4033450

Thanks Rance01.

Yes, that's it... although, in fact I'd initially expected, because my magnifying glass, in my scene, is a reasonable distance from the camera... and what is behind the glass is a reasonable distance away, behind the lens... to get the effect detailed in that physics blog link I'd posted above...

Basically the scene behind is actually shrunk, effectively, and also flipped upside down.

Least it looks like that could well happen in the real world, in the scenario I'm depicting.

What I've done so far today is now based on the shader from BionicRooster's Sherlock Holmes set, in Free Stuff here... which I discovered had a working magnifying glass shader on it already! So I've applied that to the magnifying glass prop I'm using (wanted a less ornate style of handle basically).

I need to get some reflection on it now I guess... so I expect a fresnel_blend node controlling the mix of reflection and refraction is in order... in Poser Pro 2012.

Apparently the IOR of Crown Glass (which I think is used in most reasonable grade magnifying glasses) is 1.523.

But not sure how that translates into Poser... I think I read previously that some heuristics are required?


  monkeycloud    ( ) ( posted at 4:12PM Mon, 21 January 2013 · edited on 4:14PM Mon, 21 January 2013 · @4033474


Ah, found a thread with an answer by BB, to thick glass, now...

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=3817511&ebot_calc_page#message_3817511

Which is pretty much what I thought it was going to be actually... I've read dozens of similar threads. Just not in this exact context... and I hadn't initially figured out the correlation I guess.

I've subsituted a fresnel_blend node into the basic "Reflect and Refract nodes, blended off the alt_diffuse" setup... and I suspect that's really now doing the trick (at least as far as I need it to) in combination with the convex lens, within the magnifying glass prop I'm using.

Set the IOR of the fresnel_blend node to 1.523 and then adjusting the IOR of the refract node seems to work to increase or decrease the effect... as does adjusting the radius of curvature via the morph I added.

Now... about that "visible aberation" that EnglishBob mentioned... maybe just a displacement or bump using a clouds or spots node? Either that or I make another, assymetrical, morph I guess.

I'll maybe play with that next I guess... ;)


  EnglishBob    ( ) ( posted at 4:36PM Mon, 21 January 2013  · @4033489

Quote - Now... about that "visible aberation" that EnglishBob mentioned...

I've been thinking about that. You don't mind me taking over your project, do you? :D

Chromatic aberration occurs because different colours are refracted by different amounts - so maybe you could fake it by doing three renders, one each for the R, G and B components of the lights used (i.e. turn the other two down to zero). Vary the IOR of your lens for each render, then re-combine. Only the light that's passed through the lens should be different, so the rest of the scene should recombine; if not, then a full-colour rendering will be required along with a little more compositing.  

 


  monkeycloud    ( ) ( posted at 4:46PM Mon, 21 January 2013  · @4033496

Quote - > Quote - Now... about that "visible aberation" that EnglishBob mentioned...

I've been thinking about that. You don't mind me taking over your project, do you? :D

Chromatic aberration occurs because different colours are refracted by different amounts - so maybe you could fake it by doing three renders, one each for the R, G and B components of the lights used (i.e. turn the other two down to zero). Vary the IOR of your lens for each render, then re-combine. Only the light that's passed through the lens should be different, so the rest of the scene should recombine; if not, then a full-colour rendering will be required along with a little more compositing.

Ah, okay... I think I understand what chromatic aberation is as a phenomenon, from that description.

Thanks EnglishBob :)

Hmmm... it's a tenuous link... but the Hipgnosis, Dark Side of the Moon album cover connection, that has just formed in my mind, would go rather nicely in the scene I'm doing this for actually... if I could pull that in somehow... hmmm....

I wonder if that splitting of RGB and recombining could be done in one shader though?

e.g. color_math add the result of three different Refract nodes (with R, G or B bias set for each Refract node too)... in a single shader...

I wonder...


  Rance01    ( ) ( posted at 4:47PM Mon, 21 January 2013  · @4033497


I think that may in fact be the thread where I picked up the shader I used.  My node set is a little different from yours.  I did some more testing, moving Gosha's hand away from his face and playing with the IOR.  Anyway, here's the shader I used.  The Poser MAT file is here http://www.ranquist.net/goods/IOR.zip

 

Bill's work is great.  I really appreciate everything he posts.

Be Well,
Rªnce


  monkeycloud    ( ) ( posted at 5:00PM Mon, 21 January 2013 · edited on 5:03PM Mon, 21 January 2013 · @4033507

Thanks Rance01 :)

Yes, it's essentially the same shader, I think...

I've just used the new fresnel_blend node in place of the simulated fresnel equation that BB had in that pre-Poser Pro 2012 shader... as I understand it...

...and I used ks_microfacet, instead of blinn. That choice was just based on a crystal shader, posted by LaurieA, based on input from BB, in one of her threads.


  Rance01    ( ) ( posted at 5:21PM Mon, 21 January 2013  · @4033512

Sorry was going to post a screenshot of the rainbow MAT, but I'd rather link to the original thread:

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=1881864&ebot_calc_page#message_1881864

 

gmadone, back in August of 2004.  Renderosity is a great place!


  monkeycloud    ( ) ( posted at 5:23PM Mon, 21 January 2013 · edited on 5:28PM Mon, 21 January 2013 · @4033515


Okay, on the chromatic aberration front... 

...I've got renders running in both Poser and Vue currently so I can't test it... but here's my starter idea for simulating chromatic aberration in a single shader.

Will this fly, do you think? ;-)

EDIT: whoops, changed the math_function nodes to color_math ones...


  Rance01    ( ) ( posted at 5:26PM Mon, 21 January 2013  · @4033517

Ah yea, just re-read your post.  Still using Poser 7 here.  LaurieA has some really nice shiny metal shaders too.  The magnifying glass is fun to play with -- pull Gosha's hand away from his face and at 1.4 IOR the distortion become really pronounced.  It's a nice effect and I'm glad I stumbled upon the thread with the MAT information.

Be Well,


  monkeycloud    ( ) ( posted at 5:31PM Mon, 21 January 2013  · @4033520

Quote - Ah yea, just re-read your post.  Still using Poser 7 here.  LaurieA has some really nice shiny metal shaders too.  The magnifying glass is fun to play with -- pull Gosha's hand away from his face and at 1.4 IOR the distortion become really pronounced.  It's a nice effect and I'm glad I stumbled upon the thread with the MAT information.

Be Well,

I think the great thing about a lot of BB's shaders is they're backwards compatible to Poser 7... many of them... as I understand it.

I don't really know how much different the fresnel_blend node is to that set of nodes BB has in the shader you showed there?

It's simpler to use I guess, certainly...


  monkeycloud    ( ) ( posted at 5:34PM Mon, 21 January 2013  · @4033522

Quote - Sorry was going to post a screenshot of the rainbow MAT, but I'd rather link to the original thread:

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=1881864&ebot_calc_page#message_1881864

gmadone, back in August of 2004.  Renderosity is a great place!

Wow! That's awesome! Thanks for the link :)


  Rance01    ( ) ( posted at 5:44PM Mon, 21 January 2013  · @4033524

Here's a resource for you.  Some of the goods ARE dated now - the page has been hanging for so long - but Acadia, Mistress of Links, gathered together many fine resources here:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2635126

Years ago, R'osity updated servers and many of my favorite links no longer worked.  I gathered together what I could find and hung that list online.  Acadia's list is much more detailed.

Renderosity itself - and this long running forum - is an amazing resource for learning Poser.  And the people here who have helped me in the past is manifold.

PS: my rainbow MAT has fewer nodes ... I wonder if I should re-visit that thread.


  monkeycloud    ( ) ( posted at 5:50PM Mon, 21 January 2013  · @4033526

Cool - thanks for that thread link too :)

Actually, I think I have seen that thread of Acadia's links before ... but hadn't bookmarked it... it would have been nearer the point I'd just got Poser... and I think revisiting it now, the stuff will likely make way more sense to me.


  monkeycloud    ( ) ( posted at 6:55PM Mon, 21 January 2013 · edited on 6:55PM Mon, 21 January 2013 · @4033541

Quote - Okay, on the chromatic aberration front... 

...I've got renders running in both Poser and Vue currently so I can't test it... but here's my starter idea for simulating chromatic aberration in a single shader.

Will this fly, do you think? ;-)

EDIT: whoops, changed the math_function nodes to color_math ones...

Ha! Well, from the prelimary test render, that seemed to work! :)

The difference between IORs in the three refract nodes needs to be a fair bit less though... the RGB offset was too much... but those values at least showed that it (appears, so far) to work.

I can try making some more test renders that I can share, tomorrow or so...


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