Author Topic: Terrain Altitude Blend  (Read 10302 times)

Offline efflux

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Terrain Altitude Blend
« on: March 08, 2012, 08:42:45 AM »
I meant to post this a few days ago but got sidetracked.

This is an extremely powerful technique. In fact I think it's almost necessary to get good terrains in many circumstances. I know people have utilized things like this because I've seen it but this is the way I'd do it. TG2 has some weaknesses but this is not one of them. It allows you to do it. You can altitude blend terrains so that you can get extreme variations at altitude without it effecting everywhere or you can use it subtly for beaches for example.

If you hook a fractal through Tex coord from xyz then you can use a Distribution shader for altitude.

You obviously have to think about the altitude relationship of your two terrains. Same seed for example or what displacement amplitudes they have. Same seed for two terrains but other slight differences is an obvious starting place.

Offline efflux

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Re: Terrain Altitude Blend
« Reply #1 on: March 08, 2012, 08:43:41 AM »
Here is a way that you can use this technique to good effect. I've negatively displaced a voronoi 3D A and applied strata and outcrops for the higher terrain. You can get more complex and interesting effects by subtracting a voronoi 3D A from another terrain before doing the blend or use other functions you want to modulate it about a bit since in this case, voronoi noise is a bit simple.

You will also be able to altitude blend distort as described in the other thread.
« Last Edit: March 08, 2012, 10:57:44 AM by efflux »

Offline Goms

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Re: Terrain Altitude Blend
« Reply #2 on: March 09, 2012, 04:49:19 AM »
Blending a terrain "by itself" is a nice way to get more variation. I've desribed another way to blend by "altitude" there: http://forums.planetside.co.uk/index.php?topic=4484.msg105229#msg105229

Now, the second one has great potential I think. Have you tried to also control the size of the voronoi function by altutude? If you create smaller sizes on top and let them grow to the bottom, you could almost get the basic look of a fluvial erosion on rocky terrain. Also you could try to blend out the strata to only ~20% where the voronoi cuts in, to make it look smoth-eroded.

Best regards
Sönke
Quote from: FrankB
you're never going to finish this image ;-)

Offline TheBadger

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Re: Terrain Altitude Blend
« Reply #3 on: March 10, 2012, 02:50:09 AM »
I have to say that this looks very interesting.
It has been eaten.

Offline efflux

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Re: Terrain Altitude Blend
« Reply #4 on: March 10, 2012, 09:59:54 AM »
Goms,

Yes, good ideas. I've thought of some that. I have a stepped canyon type terrain which better demonstrates the direction this can go but I'm only scratching the surface. Probably today I'll post some WIPs of what I've been doing and you'll see that. The altitude thing is a bit tricky. I tried driving sizes by altitude and it had an unexpected result. It actually seemed to squeeze the shapes vertically - but maybe that's just due to my graph. This is in fact really cool but doesn't work when you move from origin if you have displaced the shapes. That's all a bit of a mess with dodgy graphs and I'll have to go back to study it.

The great thing about blending terrains by altitude is that you can apply quite extreme effects to one part of the terrain but this won't be all over the terrain. This is one of the key successes of using this technique. You can have very jagged type rocks higher up.

One thing I found was that the very regular unnatural shapes created by the voronoi is not a problem (I thought it would be) because when you add other functions to mess that up a little, it suddenly looks quite natural.

I saw your terrain on the terrain sharing thread and you did exactly the type of thing we usually need to do to get good terrain. It's an excellent terrain.
« Last Edit: March 10, 2012, 10:01:33 AM by efflux »

Offline efflux

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Re: Terrain Altitude Blend
« Reply #5 on: March 10, 2012, 10:10:50 AM »
I have further ideas that I haven't explored yet. Severely blended terrains. Stretching them out on opposing axis and slashing them up etc then using this with altitude blend. It goes on forever as usual.

Offline Hetzen

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Re: Terrain Altitude Blend
« Reply #6 on: March 10, 2012, 10:39:22 AM »
Nice work Efflux. Those shapes do look like erosion. From what I've found, noise doesn't like being scaled through altitude, as you will always get a lateral shift towards the origin as the scale decreases.

Offline Goms

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Re: Terrain Altitude Blend
« Reply #7 on: March 10, 2012, 10:51:20 AM »
Yep, noticed that too, when trying yesterday.
But I think you also could use more then one voronoi and blend them by altitude. On top you have three, in the middle two and in the low areas only one. I will try this when I have some time to spare this weekend :)

Quote from: FrankB
you're never going to finish this image ;-)

Offline efflux

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Re: Terrain Altitude Blend
« Reply #8 on: March 12, 2012, 01:25:48 PM »
Here's one where I simply ignored whether one terrain relates to another in the "right way". The sharper terrain also supplies a little warping.

Offline AP

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Re: Terrain Altitude Blend
« Reply #9 on: March 12, 2012, 11:16:09 PM »
Don't mean to highjack this thread with images, however i found a couple of images of a world's surface and sky from the upcoming film Prometheus and thought that the terrains on that world would compliment what you are doing here.

Offline efflux

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Re: Terrain Altitude Blend
« Reply #10 on: March 13, 2012, 02:24:37 AM »
Yes, that looks similar.

I'm pretty much done with the altitude blend thing on here. That's fairly straightforward but I'm definitely interested to explore the voronoi thing way more. You can also subtract the voronoi rather than negatively displace but that's much of a muchness. Just slightly different results. I've added an image of another terrain in my WIP thread where I've furthered this with more voronoi layers.

Offline efflux

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Re: Terrain Altitude Blend
« Reply #11 on: March 13, 2012, 02:35:08 AM »
Goms.

You can create smaller voronoi and stack them up by clamping them but then you have to bring the clamped value back to 0. I just haven't created a specific graph for that. It might work in this scenario.

Offline AP

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Re: Terrain Altitude Blend
« Reply #12 on: March 13, 2012, 03:11:02 AM »
Yes, that looks similar.

I'm pretty much done with the altitude blend thing on here. That's fairly straightforward but I'm definitely interested to explore the voronoi thing way more. You can also subtract the voronoi rather than negatively displace but that's much of a muchness. Just slightly different results. I've added an image of another terrain in my WIP thread where I've furthered this with more voronoi layers.

The only element i see missing in your results as opposed to the film terrain is i noticed some deep vertical cuts scattered about the inclines. Could be deep, long erosion but there should be a procedural way of figuring this out i would hope. There may be a case were the strata is warped as well in certain zones and not all straight.

Offline efflux

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Re: Terrain Altitude Blend
« Reply #13 on: March 13, 2012, 03:19:10 AM »
You can cut terrain up by blending one with another, especially if it's stretched out on an axis. The next phase would be to experiment with the voronoi technique but on more complex terrain. I've done this with a heavily stepped terrain which is obviously ideal for it.

I think you can almost do anything with TG2 except make erosions which are quite flat like rivers etc. We have the Alpine Fractal which goes a bit in this direction but I've noticed there is a nasty problem with that shader. You get horrible vertical breakages.

Offline efflux

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Re: Terrain Altitude Blend
« Reply #14 on: March 14, 2012, 11:42:43 PM »
Forget that I mentioned voronoi "subtraction" which I've talked about a few times. That creates some problems. The negative displacement for the voronoi in the file provided earlier is the way to go.

I've got a new terrain every 5 minutes here. I'm still only using voronoi. Here is a screenshot that will hint at how I did the terrain in the picture and why it works with this technique used in this thread plus the voronoi on the slopes. It's based on the second file posted here. Terrain displacement has a low spike limit setting - I usually keep that low to avoid extreme spikes. The chain of voronoi are obviously different sizes and different displacement values. This is a dead easy way to create interesting terrains. Took me one minute to create this terrain. Where the bias is, try other maths functions. Try a smooth step etc etc.
« Last Edit: March 15, 2012, 01:30:51 AM by efflux »