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Diamond ring

Posted: Fri Jun 13, 2008 9:43 pm
by tobak30
Need a good diamond material for this ring here. And what is the .nk material for white gold?

And how to get the entire ring in focus. The ring is in fact scaled down to 0.017 blender units. Which after my calculations should be 1,7 centimetre.

Thanks for all replies.

Posted: Fri Jun 13, 2008 10:10 pm
by SmartDen
just add couchy_b_coeff 0.03941 or something alike. search the forum

Posted: Sat Jun 14, 2008 12:27 am
by ViennaLinux
and for the sharpness .. do NOT open the camera lense that wide....

so set the F stop value to something high .. to be on the save side take 32.
tell me if that solved it ;-)

Posted: Sat Jun 14, 2008 11:39 am
by zsouthboy
Ah yes, the macro shot.

In real life, we photogs have to use an insane aperture value to get any DOF at all - something like f/32 to f/64.

Try that and see what you get.

EDIT: oh and should've mentioned - there's no .nk for white gold. Try using the Specular Reflectivity setting with a light yellow as your base color?

Posted: Sat Jun 14, 2008 7:03 pm
by tobak30
I rendered this piece with an f/64. Does it help to resize the camera or something like that?

Posted: Sat Jun 14, 2008 11:31 pm
by Kram1032
O.o how big (or small) is that ring?

The cam is a dot, so to say... A dot which shoots rays in all the directions, where you see something on your screen.

An other way to reduce DoF is to use a more zoomed lens, I think...
(So, but your camera further away but adjust the filmsize in order to get the same effect...)
- though, this causes things to look flat ;)

Posted: Sat Jun 14, 2008 11:38 pm
by tobak30
hmm. okay. I mentioned how big the ring is in hte first picture. Its diameter is 1.7 cm.

Posted: Sat Jun 14, 2008 11:42 pm
by Kram1032
oh sorry^^

The inner or the outer diameter?
If it still doesn't work, you might want to scale it up (although that's just if you get impatient with getting it sharp, as it simply would be wrong^^)

Posted: Sun Jun 15, 2008 12:10 am
by tobak30
its the outer diameter of the ring.

What filmsize would i have? I got the 35 mm film in blendigo. Shoul i set it to a higher value?

Posted: Sun Jun 15, 2008 12:17 am
by Kram1032
I think higher, yes... Though, you need to adjust the camera in blender. Setting it higher means zooming in...
There also is a setting inside blender...

Posted: Sun Jun 15, 2008 2:22 am
by zsouthboy
No no no Kram :P

Both higher focal length and wider film DECREASE apparent DoF.


If you're okay with it, I'd love to take a look at the blender scene - f/64 can end up being less than a few cm of DoF if you are focused a few cm from the "lens"

Posted: Sun Jun 15, 2008 4:59 am
by Kram1032
ok, then do the other way round... xD (in that case, your render gets pretty distorted, though)

Posted: Thu Jun 19, 2008 7:37 pm
by tobak30
Here is the file for your enjoyment. i have changed some things there as there are a closed cube now and 2 mesh lights.

Posted: Fri Jun 20, 2008 2:31 am
by zsouthboy
Thanks tobak, I'll take a look.


That's quite small!

It's a pain working at such small sizes - here's a tip: create your scenes at 10x real scale (so that it's easier to work with), then use the "Scene Scale" adjustment in Blendigo to reduce it on export! So much easier than dealing with blender and very small units :)

EDIT2: Real diamond has an IOR of 2.417ish - i'm looking up the cauchy or sellmier measurement now

Couldn't find a cauchy number anywhere, but .04 as you had it looks good.
To fix your focus, I changed the focal length to 125mm and instead moved the camera slightly closer to compensate, then changed the film width to 22mm.

EDIT4: Well that improves the situation, but does not fix it. I'm going to just change the aperture size directly, because f/64 isn't high enough for this particular scene.

Posted: Fri Jun 20, 2008 4:09 am
by zsouthboy
Okay, here is the changed blend.

Changes from yours:
Scene scaled by 10x.
The modifiers you had on the ring caused holes in the mesh to appear (edgesplit then subsurf) - I approximated what you intended with bevel then subsurf then edgesplit.
Ground plane moved up to make ring "rest" on it.
Camera focal length changed to 125mm.
Camera moved closer to compensate.
IOR for diamond changed to 2.417
Scene scale setting in blendigo set to .1x

Upon export:
go into default.igs and add four zeroes after the decimal point for "aperture width"