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Pete Michaud 01-06-2008 02:59 PM

Star Field Techniques
 
I have a technique that I use to lay down the base of a star field a la Greg Martin, but it doesn't work at high resolutions. Because it uses noise, which can't be natively scaled, it only works at fairly small resolutions, which I've historically just scaled up and hoped for the best.

That works to an extent, if the scale is less than one order of magnitude, and the star field isn't the focus of the painting, but I'm trying to produce a piece that's 9000x7200 pixels, the subject being predominantly outer space-- the scaling looks awful!

What are some good resolution independent techniques to produce nice star fields?

Kutkin 01-06-2008 04:14 PM

I don't know if I understand correctly. I don't know where's the problem. If you have problems creating good stars at certain resolution, then create them in a different one and scale them. For big ones you can create even bigger ones and scale down. Or tile some smaller ones.
http://pavelcucka.com/web_images/stars.jpg

nickmarshallvfx 01-06-2008 06:39 PM

I have had the same problem when creating starfields using Greg Martins technique as a base. No idea why it is, but it has me stumped too...
The technique seems to work fine at up to 1k resolution, but after that it just doesn't seem to work...
I had to do a 4k painting of a starfield recently, and found that if i scale the noise uo loads it seems to work. Try just scaling the noise up significantly when you are working. Sorry i cant offer anything more solid...

Nick

Xdreamer79 01-07-2008 04:25 AM

Hmm for me this always worked just right. I mean you can always do a highres of your starfield using his technique and scale down...I never tried to upscale any of his starfields, might give that a try and looking at the outcome :)

s0nkite 01-07-2008 06:24 AM

just duplicate that layer and place it in diferent positions etc till is not noticable tiling ROFL very hard :roll:

Pete Michaud 01-07-2008 07:10 AM

Well, the issue is that noise changes tones per pixel, so in general a pixel is the size of any given star when using that technique--in later steps they get a little bigger, but not much. At larger resolutions, those "star pixels" were invisible at normal viewing distances, so the only thing you could do is scale them up by about 2000% in my case. At that scale the artifacts are unacceptable.

Just stitching smaller fields doesn't actually make anything better -- it makes a great extremely large star field at very low resolution, but not such a great normal sized, high resolution star field.

However, I figured out a way! I'll post the actual settings for the brush later today maybe, but I came up with a brush in photoshop that looks dead on like the base star field-- I'm really happy with how it looks, and it's WAY easier to use than greg martin's technique. It's far more flexible because it's a brush, so you can paint in any color, over any background, with any number of layers.

You can create a similar brush easily -- for my 9000x7200 resolution, my basic shape was 50px. I set the roundness to 80%, hardness to something high but not quite 100%. I then set the dynamics such that each star is a different opacity, size, and rotation. I gave it a wide scatter area to get randomness. I'll post all the settings later, like I said, but it's easy to set up if you play around with it. It's also super easy to scale it up and down for whatever resolution you're using.

oversheep 01-07-2008 08:29 AM

Yep, I'm with Pete, I think that with a good brush may be a good way to get nice result whatever the resolution...

itsmeyatin 01-07-2008 10:13 AM

hey

i would rather do this in 3ds studio max using video post than painting it.
and than edit my renders to my pref.its just lets me work faster!

Pete Michaud 01-07-2008 05:38 PM

Sure, if you have 3ds and you don't mind it looking a bit computer generated, that's fine.

The easiest way for me to give the brush is to just describe the settings I have on each brush option per tab:

Brush Tip Shape:
-Diameter: 30px (this is set up to default for a 5000px canvas, you can adjust this to your preference, even after this is complete)
-Angle: 30
-Roundness: 80%
-Hardness:66%
-Spacing:1000%

Shape Dynamics:
-Size Jitter 25% (Control:Pen Pressure)
-Min Diameter: 0%
-Angle Jitter: 100% (Control off)
-Roundness Jitter: 10% (control off)
-min Roundness: 25%

Scattering:
-Scatter:1000%(Control Off, Both Axes Checked)
-Count: 3
-Count Jitter:0%

Other Dynamics:
Opacity Jitter: 100% (Control Off)
Flow Jitter: 100% (Control Pen Pressure)

Smoothing Checked


These are my settings, and I think they give great results!

nickmarshallvfx 01-07-2008 05:48 PM

Thanks Pete im gonna make that brush when i have a spare minute and ill let you know how it is.

Nick


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