Don't understand Twist and Shear's Base altitude

Started by Alf15000, May 08, 2013, 06:16:07 am

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Hi all !

I'm doing tests with Twist and Shear Shader, but I don't understand how base altitude works.

My example is a "pilar" based on a cube :

I set Twist and Shear's Base Altitude at 0.5. I think that effect of this shader should be effective above half (0.5) of total altitude (200) like that (done with Photoshop) : 

Instead of this, I've got that :

So my question is : what is base altitude supposed to do ?

Thank you for answers :-)


I think it's the altitude from where the effect starts to kick in....what I know for certain is that it is in metres and not as a proportion as you thought.
(just think: how would this shader/node "know" that your tower is 200m tall? Or even more complex: how would such a proportion work on a terrain? I don't know)


Just don't use it, but blend it by a distribution shader with a fuzzy zone, for smooth bends.


May 08, 2013, 07:35:04 am #3 Last Edit: May 08, 2013, 07:36:37 am by Alf15000
Thank you for your answers... I tried with meters, results are the same. And as Base altitude "range" is [0-1], I thought it was "in proportions".

I think about a distribution shader as Dune said, but I like to understand and I don't think Base altitude is only here for "decoration" ;-)


Well some settings are for decoration unfortunately.
Try the base altitude for strata&outcrops. I haven't been able to get it to work either.
Also in some occassions "fit blendshader" does nothing (it's unclear anyway what it really does).


Lol ! Same thing for me with Power Fractal's Adjust Coastline... It reassures me that I'm not the only Terragen 2 user's who have decoration settings :-)

However, it not really helps for understanding Terragen 2's settings that are already difficult to understand ;-)


The latter does work, although I never use it.


Thank you Dune !  :)

I better understand Adjust Coastline ! That wasn't the subject of this topic, but it still helps me :-)


I have read somewhere the base altitude control the pivot position of the shear effect.
So basically it doesnt change the overall result of the effect.

At altutide 0%, the base postion dont move
At altutide 50%the base and top position move

The altitude as to be set in meter of course.



Excellent ! During my tests, I found that my "pilar" moved when base altitude changed, but I didn't managed to understand why his shape didn't change...

Your sketch is really understandable ! Thank you paq :)


I think the base altitude may be the altitude above the planet sphere, not the altitude above the terrain's surface. Your "base" may be hidden below the terrain.


Paq's diagram is correct. Nicely illustrated.

- Oshyan



Would you be able to describe the node network for using the distribution shader to blend the twist and shear shader please.

I'm trying to create a pillar with a "Tim Burton-esque" curl to it.
So far I have a circle simple shape shader displaced with a smooth step.
I've tried using a merge shader but its not working out how I was expecting.




Thnx Dune,

I had a look, great to see an example of using the surface layer.
I edited the network to use only the first twist and shear and it was what I had in mind.