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General => Terragen Discussion => Topic started by: hehe on January 19, 2007, 01:59:36 AM

Title: how to make snow edges follow terrain?
Post by: hehe on January 19, 2007, 01:59:36 AM
Hi I am wondering if anyone has any advice on making the edge of the snow line in TG2 that will follow the contour of the terrain so that the edge is not soft or blended but has fingers of snow that lay in the ravines and crevices and low lying areas at the snow line?

examples: http://vulcan.wr.usgs.gov/Imgs/Jpg/Shasta/Images/Shasta84_mount_shasta_with_shastina_1984.jpg

and here  http://www.amorahquanyin.com/images/shasta-ground.jpg

and here  http://www.geol.binghamton.edu/faculty/dickman/mt-fuji.jpg

Thank you very much for any advice
Title: Re: how to make snow edges follow terrain?
Post by: FrankB on January 19, 2007, 03:22:20 AM
I've done that once for TG0.9.

If you have World Machine, erode your terrain and have WM create you a thalus mask. Use that mask for your terrain to mask out the snow. This can give you a starting point.

Cheers,
Frank
Title: Re: how to make snow edges follow terrain?
Post by: Oshyan on January 19, 2007, 03:27:26 AM
Using simple slope constraints can get you a good part of the way to that effect. You should also experiment with "Intersect Underlying" in the Surface Layer.

- Oshyan
Title: Re: how to make snow edges follow terrain?
Post by: oggyb on January 19, 2007, 08:20:29 AM
Hi Oshyan, what does "intersect underlying" actually do?  And why does it need smoothing on?

M.
Title: Re: how to make snow edges follow terrain?
Post by: Volker Harun on January 19, 2007, 10:24:30 AM
When you load a terrain in worldmachine, you can run an erosion-filter on it.

Just put a fileoutput at the end of the node (called flowmap)  and you have a nice mask, where erosion (or snow) would walk along (snow would stay).

Applying this mask to a distributionshader (slope and altitude-settings) would make your effect.

V.Harun
Title: Re: how to make snow edges follow terrain?
Post by: Matt on March 25, 2007, 12:35:41 AM
As Oshyan suggests, "Intersect underlying" is designed to help with this kind of problem, but a couple of days ago I discovered that it is currently broken. I have now fixed it (for the next update), and I've been doing some tests with it to see if I can improve it while I'm there. I will try to put together some examples to explain its purpose and how to use it.

Matt
Title: Re: how to make snow edges follow terrain?
Post by: dhavalmistry on March 25, 2007, 12:55:59 AM
Quote from: Matt on March 25, 2007, 12:35:41 AM
As Oshyan suggests, "Intersect underlying" is designed to help with this kind of problem, but a couple of days ago I discovered that it is currently broken. I have now fixed it (for the next update), and I've been doing some tests with it to see if I can improve it while I'm there. I will try to put together some examples to explain its purpose and how to use it.

Matt


thank you....this is a miracle....the main purpose of me coming to this forum at this time (1:00 AM) was to make new topic about intersect underlaying and here it is...first post in the forum....I didnt even have to make new topic....
Title: Re: how to make snow edges follow terrain?
Post by: Matt on March 25, 2007, 01:04:30 AM
Magic :-)
Title: Re: how to make snow edges follow terrain?
Post by: VorpalBlade on March 25, 2007, 02:46:01 AM
I bet you can generate a density map that follows the valleys down using WM. I may give this a try when I get home.

Edit: Volker beat me to the puch on the WM suggestion  :-\
Title: Re: how to make snow edges follow terrain?
Post by: reck on September 09, 2007, 07:02:38 PM
Quote from: Matt on March 25, 2007, 12:35:41 AM
As Oshyan suggests, "Intersect underlying" is designed to help with this kind of problem, but a couple of days ago I discovered that it is currently broken. I have now fixed it (for the next update), and I've been doing some tests with it to see if I can improve it while I'm there. I will try to put together some examples to explain its purpose and how to use it.

Matt


Can someone please explain to me what/how Intersect underlying does? It's been altered/improved in the latest update but I don't really understand what it does so I don't know when to use it. Thanks.
Title: Re: how to make snow edges follow terrain?
Post by: Tangled-Universe on September 10, 2007, 08:02:35 AM
Yes that would be really nice! :)
Maybe someone could also explain how to apply a flowmap 1:1 onto the terrain?
I've been struggling with it for a while. I know you have to set the size of your image the same as the size of your terrain in meters. But when I do that and I apply a bright blue/red colour to the mask the flowmap doesn't match the terrain at all. So anybody who knows?
Thanks in advance.

Martin
Title: Re: how to make snow edges follow terrain?
Post by: bigben on September 10, 2007, 08:54:45 AM
Quote from: Tangled-Universe on September 10, 2007, 08:02:35 AM
...Maybe someone could also explain how to apply a flowmap 1:1 onto the terrain?
I've been struggling with it for a while. I know you have to set the size of your image the same as the size of your terrain in meters. But when I do that and I apply a bright blue/red colour to the mask the flowmap doesn't match the terrain at all. So anybody who knows?

Usual things that go wrong:
Make sure placement of terrain and image are the same (centre or lower left), same coordinates and size.
Default projection for images is Through camera... needs to be PlanY to match the terrain.

The placement of snow will vary depending on a number of factors...
More snow in gullies ... start of snow season, snow in exposed areas melts more quickly
More snow on slopes/ridges ... running water from melting snow removes snow from gullies
No snow on ridges or in gullies ... last snow remaining in patches on steeper slopes shaded from the sun
Title: Re: how to make snow edges follow terrain?
Post by: Harvey Birdman on September 10, 2007, 11:29:59 AM
Quote from: bigben on September 10, 2007, 08:54:45 AM
The placement of snow will vary depending on a number of factors...
More snow in gullies ... start of snow season, snow in exposed areas melts more quickly
More snow on slopes/ridges ... running water from melting snow removes snow from gullies
No snow on ridges or in gullies ... last snow remaining in patches on steeper slopes shaded from the sun

So Ben ... you seem to have a lot of experience with snow for an Aussie! What's the deal?

;) ;D ;D
Title: Re: how to make snow edges follow terrain?
Post by: FrankB on September 10, 2007, 12:47:12 PM
Actually, "Intersect Underlying" is fixed with the latest version. Combined with slope and altitude constraints, this should give you what you need.
It's sorta tricky to exactly configure the feature for your specific terrain, (because Matt has yet to reveal how it really works), but you can get it done with a little try & error.

My take on it's functionality is, that it identifies either depressions or raises on the terrain.
The intersect zone defines how large the area is to take into account for identifying e.g. a depression. (you can define the room between your little fake stones as depressions, or use larger depressions such as found with mountain erosion.
Then, Intersect Shift shall let you define if the areas identified shall be lifted up or down by the specified amount.
I "guess" that minimum intersection shift is similair to an offset for the Intersection Shift.

Good luck,
Frank
Title: Re: how to make snow edges follow terrain?
Post by: ADE on September 10, 2007, 12:53:54 PM
done one here just last week....using intersect underlying and smooth bunged up to 2 with a little diplacement you can get snow that looks like its been shovelled into heaps...ok for snow plough scenes i spose
http://www.ashundar.com/index.php?action=dlattach;topic=3964.0;attach=173;image
Title: Re: how to make snow edges follow terrain?
Post by: bigben on September 10, 2007, 06:56:18 PM
Quote from: Harvey Birdman on September 10, 2007, 11:29:59 AM

So Ben ... you seem to have a lot of experience with snow for an Aussie! What's the deal?

;) ;D ;D

I've hiked through snow in Scotland?? :)

True, our snow sucks most of the time (we just don't have the elevation), but even with a little snow it has it's moments:
http://www.path.unimelb.edu.au/~bernardk/victoria/virtual/howitt.html (http://www.path.unimelb.edu.au/~bernardk/victoria/virtual/howitt.html)
http://www.path.unimelb.edu.au/~bernardk/victoria/virtual/pieman.html (http://www.path.unimelb.edu.au/~bernardk/victoria/virtual/pieman.html)

But otherwise I just tend to over-analyse pictures to figure out how to make more realistic renders ;)  Tree Canopy maps actually give you similar distribution variations....
Alpine areas - rock laden floods clear river beds
Flat farmland - farmers tend to leave trees along rivers and clear everything else
Title: Re: how to make snow edges follow terrain?
Post by: Harvey Birdman on September 10, 2007, 07:18:37 PM
Well, I'll be damned. I thought the only thing down under that even started to look like a mountain was Ayers (sp?) Rock. Pardon my ignorance.

Ever do any climbing in New Zealand? I swear if I lived as close as you I'd fly there every summer for vacation.
Title: Re: how to make snow edges follow terrain?
Post by: bigben on September 10, 2007, 08:15:39 PM
Quote from: Harvey Birdman on September 10, 2007, 07:18:37 PM
Well, I'll be damned. I thought the only thing down under that even started to look like a mountain was Ayers (sp?) Rock. ..

Careful viewpoint selection  ;)  Our highest peaks are around the same as the UK.... there's just wee bit more flat land around them. My methylated spirits camp stove works just fine everywhere here :) 

NZ would be good though...
Title: Re: how to make snow edges follow terrain?
Post by: bigben on September 17, 2007, 07:27:54 PM
I was working on my Mt St Helens terrain for a bit and tried some of the new intersect underlying settings.  I don't have a render on hand, but I can definitely recommend giving the new settings a try. Favour ridges/gullies at a quick glance is an awesome feature and may reduce the need for flow maps (providing much better results). It may also be useful for creating masks even if there is no/very small displacement used to set the selection of terrain. Definitely one worth exploring.  ;D
Title: Re: how to make snow edges follow terrain?
Post by: Volker Harun on September 18, 2007, 04:45:41 AM
I found it useful to check 'Terrain normal' when using intersect underlying.
It is easier to control.