Question about adding cascade terrains

Started by alessandro, December 02, 2013, 07:09:52 pm

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alessandro

I've successfully tested how to add multiple heightfields or surface layers to an initial fractal terrain (Power Fractal Shader), in order to create smaller and more defined terrain areas.
Now I was trying to add a second PFS after the initial fractal terrain, but in order to get positive heights I need to use a negative 'Displacement amplitude': using a positive one will actually create a crater.
Attached is the test.tgd file: would somebody be so kind to tell me what I'm doing wrong, or if it's supposed to be this way? Thanks :)


Dune

December 03, 2013, 03:26:03 am #1 Last Edit: December 03, 2013, 03:27:55 am by Dune
I don't really understand what you need, a crater or a mountain? It's a mountain with this negative displacement. But you can play with the offset to raise or lower the whole area. Or you could use a surface shader under the initial terrain, masked by the simple shape, set it to smooth terrain (it'll annihilate all previous displacement until it hits a compute terrain), and then add your second PF terrain masked by the same SSS or maybe as a child to that surface shader.

alessandro

I wanted to add a mountain to the initial PF terrain. But yes, the second part of your answer actually works and that's what I needed to understand. Thanks

Mohawk20

I haven't looked at your file, but did you add all the heightfields and terrain fractals before or after the compute terrain node?
You can also use several compute terrain nodes if your network requires it.
Howgh!

alessandro

The attached file is extremely simplistic but usually yes, I add all large terrains before Compute Terrain, and later I add colors and eventually minor displacement nodes for smaller parts of terrains. Those displacement nodes that I add after Compute Terrain seem to work, so I was wondering why would you call Compute Terrain multiple times in a project?

Dune

If you need some lateral displacements for instance, you might need the terrain to be computed (for the new normals), but if you can leave it at one compute tarrain, all the better, as every compute terrain adds enormously to render time. Sometimes you don't even need a compute terrain  ???


bobbystahr

Quote from: Dune on December 03, 2013, 03:26:03 am
I don't really understand what you need, a crater or a mountain? It's a mountain with this negative displacement. But you can play with the offset to raise or lower the whole area. Or you could use a surface shader under the initial terrain, masked by the simple shape, set it to smooth terrain (it'll annihilate all previous displacement until it hits a compute terrain), and then add your second PF terrain masked by the same SSS or maybe as a child to that surface shader.

great method...will play with the 2nd part as well....
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist

Oshyan

The reason this is happening is because the Power Fractal has both negative and positive values, it displaces from a baseline of 0 (planet radius) both up and down. If you Randomize the noise seed of your Power Fractal you'll see it's sometimes up, sometimes down, depending on the noise characteristics at that particular point. You can use the offset as Dune mentioned, if you want to be sure of positive values.

- Oshyan

Dune

Or you could use the color of a PF to drive a displacement shader. That'll go one way (up or down). You only have to take care of the color roughness.