EnigmA Amiga Run 1998 July/EnigmA AMIGA RUN 29 (1998)(G.R. Edizioni)(IT)[!][issue 1998-07 & 08].iso/recent/iib122.lha/IIB/Threads/Creating_Diamonds

Internet Message Format | 1998-02-17 | 7KB

Date:         Tue, 30 Sep 1997 16:24:41 -0700
From: "Hall, Michael R." <[e-mail]>
Subject:      [IML] Quest: Creating Diamonds

Hi gang,

I'm embarking on a new project for work and I could use a little advice.

I have been instructed to create a splash screen for a program that I am
helping to design.  The image is supposed to be a few lumps of shattered
coal exposing gleaming diamonds.   The environment would likely be a
battered work table with a hammer and a few other chiseling type tools on
it.

What I am looking for is advice on how to create the diamond.  I remember a
recent post about Kathryn Foston's creation of a diamond and I understand
that I will likely have to render the scene at least three times with
different refraction values to get a realistic sparkle to the diamonds, but
I was wondering how to combine the separate rendered images into one?  I
have Photoshop 4.0 and am pretty good with it, but I don't know of a
technique that will take multiple images and average them into one in the
fashion I desire.  I suppose I could copy each image into a separate layer
and then set the transparency of each layer to a percentage equal to the
total number of images (say there are three image layers, each layer would
have a transparency of 33%).

Any clues?  Also, any further suggestions on the creation of the diamond or
rendering of it would be greatly appreciated.  I was just given this
assignment today, but it has a really tight deadline.

Oh, could anyone who responds respond to me via my private email (as well
as to the list, if you like)?  I get the list in digest format and would
have to wait until tomorrow night to receive mail otherwise.

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Date:         Wed, 14 Jan 1998 23:49:40 -0000
From: Richard Jennings <[e-mail]>

To create a "standard" diamond :

Add a primitive cone Radius=50, Height=50,
Circle Sections=2, Vertical Section=2.
Uncheck Stagger Points and check Close
bottom. In points mode select the 12 points
that make up the base. Interactively scale
these to around .25. Then move them closer
to the rest of the cone (i.e. along the Z axis).
Finally in Attributes turn off phong shading.

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Date:         Thu, 2 Oct 1997 01:21:09 +0800
From: Kathryn Foston <[e-mail]>

Well, what I did to get the sparkles was to create the diamond with 3
states, each with a different IOR. Now, some people render the 3 different
images, then extract the RGB info from each pic then combine them. I thought
that was unnecessary, so what I did was to set up 3 different projects and
each project had different coloured lights, RGB.

Now in Photoshop (or Premiere, which I used for the anim), just put each
image on a separate layer, and use "screen" compositing.

Simple as that!!

As for the attributes of the diamond, base colour, specular and filter were
set to white,  the 3 IOR's at 2.1, 2.3 & 2.5.

I used ABFakley for reflectance with the front colour at 38 on all guns, and
the side colour at 92. I then used ABFakeNC for hardness, with the front at
75 and the side at 40. Then add ABBoost with 1.5 for colour and 1.2 for
specular

Don't forget you can still download the mpeg from my gallery. Although
remember, that even with this technique, you won't get accurate sparkles, as
it's not possible with raytracing, but you get a pretty good approximation
;)

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Date:         Wed, 1 Oct 1997 06:18:36 +0100
From: Richard Jennings <[e-mail]>

There is a program called prisms that
will combine three pictures rendered
with three different IOR values for any
glass type objects. The resulting picture
will then have chromatic despersion.

Let me know if your interested........

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Date:         Wed, 1 Oct 1997 18:26:00 +0100
From: Richard Jennings <[e-mail]>

The prisms program for doing chromatic
dispersion is on my web site under
"Free Graphics Programs". URL below

It is only a 23K download. There is also
a picture generated using it on the
same page.

Richard Jennings (RJJ)
Mail Me          [e-mail]
Visit Me   http://freespace.virgin.net/r.jennings

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Date:         Sat, 10 Jan 1998 08:55:42 -0500
From: Pat Connelly <[e-mail]>

>Hi to all
>
>Some times ago (I think around Sept. or Oct. 1997) someone post a web-site
>address for a tutorial on how create diamonds. Incidentally I have deleted
>this mail, can someone, or the author himself, repost it, please.
>
>Thank you in advance
>Salvatore

From: Tim Wilson [Crestline] <[e-mail]>
Subject: Diamonds and Crystals
Date: Thu, 13 Jun 96 07:00:00
----------------------------------
To Nancy Jacobs re your ``RENDERING QUESTION'' message of Tue, 11 Jun 1996:
>>>I'm struggling for the ultimate solid light-emitting crystal effect. Any
ideas? Making progress, but it's not there yet.<<<
Diamonds have a large index of refraction (2.41) and small angle of total
internal reflection. Translation: they can be cut so that virtually all light
entering the gem is reflected out the front, giving them a brilliant flash.
They are also highly dispersive. Translation: spread light out into spectral
colors, like a prism. Imagine can't really simulate the optics of either of
these effects.
My suggestion would be to distribute several lights around the scene, make the
gem Transparent, make sure it has a nice variety of facets, set the Specularity
high (perhaps to the max), and play with the Hardness, until it looks good.

I suppose you could add a little Reflectivity, to get some internal
reflections, but you might want to simplify, set the
reflect/environment/global/specularity maps aside, and focus just on getting
the specularity right first. Specularity simulates the reflection of a light
source, which is probably the most prominent feature of a gem.

If you want the illusion of the spectral colors you might try making a ring
of spectral colored lights around the front of your object, so you get
different colored specular highlights. Perhaps with a few bright white
sources mixed in. Or you could experiment with adding small spectral patterns
into your environment/global map.

To get a ``glow'', take a copy of your rendering and run a gaussian
blur on it, and then additively composite the blurred image at,
say 20- 30% on top of your original rendering.

Some movement of the objects or lights might also help to add some sparkle.
-Tim

Is this what you were looking for?

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Date:         Sat, 10 Jan 1998 11:05:37 -0600
From: CJO <[e-mail]>
Organization: Prodigy Internet

hey salvatore
I have a 3ds model of a diamond I could Email it to you if you would
like.if you dont have a converter I can convert it to any format you
like
chris johnson

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Date:         Sun, 11 Jan 1998 11:43:15 +1030
From: Dan <[e-mail]>
I saw a nice diamond on Aminet recently
at
http://ftp.wustl.edu/~aminet/dirs/gfx_3dobj.html
its only a 4k file, but I wont mail it with this as not to annoy ppl.
If you can't find it let me know and I'll mail you the copy I
downloaded.

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