Joshua Tree National Park first WIP

[mhaze]

Really enjoying this one - great scene with interesting development. Look forward to the finished result

[gregtee]

Hey Dune,

Choronr was kind enough to post a tgc file that handles the ripples in the manner you described which I've hooked into the flow.  The issue was I just couldn't get them sit where I wanted.  They looked great on flat areas but fell apart on anything else.  I think I need to build a very simplified scene first and just get it working there before trying to meld into something as complex as what I've bulit up so far.  I also need to learn to label my stuff better so I know what the hell I'm doing.  My Nuke scripts are only marginally better organized, and that's just so I don't get laughed at work if I need to pass one off to someone who actually knows what they're doing. 

With regards to the sand ripples, the file Choronr posted had ripples with sharp cusps.  I adjusted this by changing the ridge smoothing so they weren't so sharp.  They feel more natural now, but what I'd really like to do is shift the bias of the cusp across the ripple so it favors one side or the other, so instead of the highest point of the cusp of the ripple always being center ripple, it would maybe closer to the edge of the ripple.  Is this possible?

I'll post something later today for everyone to get a chuckle at. 
Thanks again everyone for all the help.

[gregtee]

Another question Dune,

I'm using a Surface Layer to add the sand ripples shader, which I assume is the correct approach. 

Next I've selected Displacement Intersection under the Effects tab as the method of displacement merge.  I've left off Intersect underlying as it didn't seem to do anything.  I've set the appropriate altitude and slope constraints to limit the sand ripples to just the parts that I want.  Now here's the problem:  When I connect the sand shader to the Child Layers input triangle on the now configured Surface Layer, about half of the main displacements from the main upstream flow from the Input Node vanish.  Only the biggest displacements reamain.  All the lower level stuff vanishes, stuff that's still above the sand level.  It shows properly when I don't have the sand ripples input and am just using Enable Test Color to verify everything's working, but the moment I add the ripples as the child have the terrain displacements vanish. 

Any insight?

Thanks again

Greg

[Jo Kariboo]

I very like the first one !!!

[Dune]

The tgc with the ripples was made before the new fractal settings were on board, hence the sharpness. And I know what you mean about the shifted top, having experimented with that as well. I don't think I can find those experiments easily, but remember it was done with an additional cosinus of the same X to scalar, and bias add or subtract functions. I'm sure some of the Math guys have excellent solutions for this. If I find something I'll post, but don't hold your breath.`You could also try something with a tilt and shear shader to shift the tops a little to one side.

If you have the x to scalar + sinus set up, you have straight soft lines, if you could add a number to this base and thus shift the line a little to one side, you could add or multiply these values for a bias to one side, then continue with the rest of the line of shaders.

The problem with the vanishing of the rocks has to do with the compute terrain patch size; if you decrease that they will (probably) re-appear. And/or changing the values to smaller values in the displacement intersection.

Hope this gets you on the way....

EDIT: I quickly put some nodes together, but I'm sure there's a better way.

[gregtee]

Well Dune you've certainly given my a lot to think about.  I've set up render that'll take about 2 hours to compute.  I'll put it up when it's done using these new sand ripple ideas. 

Thanks again

-Greg

[gregtee]

Well here's what I've managed thus far with the sand ripples:

[attach=1]

Overall I think they're working.  I still would like to make the texture of them have a little more variation in color, tone, and size of individual sand grains, but that's just fiddling at this point.  It feels a little too powdery still.  Also once I've got this to where I like I need to start adding all the dead little twigs and other debris one sees on the ground in places like this.  Still a little too sterile at this point.  I'm still looking for some tall grasses if anyone knows where to find these things here on the forum.  I've looked and haven't found much.  I saw some Walli posts that looked promising but the links were dead.



thanks again for all the comments and help everyone.

-Greg

[Dune]

With some no-displacement colored fractals and/or surface layers of color you have your color variation in no time. And you might need to add some warp to the ridges to make them more diverse and 'windblown'.

[gregtee]

I was playing with a fractal warp on the ridges at one point but removed it when I was trouble shooting something else.  I'll have to put it back on. Thanks for the reminder. 

[zaxxon]

Greg, if you're still using Speedtree in this project then perhaps the grass primitive in the ST geometry types might serve your purpose. The sand color seems to have a 'temperature' value much 'cooler' then the mid ground values to my eye, but the flow of the composition with the ripples looks great.

[gregtee]

Thanks zaxxon, I'll take a look at Speedtree grass primitives.  I still intend to adjust the color of the sand, because you're right, it feels temperature wise a little out of place and dull.  I also think some of the cuts in the sand feel a little "cuspy" and hard edged, something I think adding a fractal warper might help adjust.  I'm also thinking about bringing back some of the old ground level rock stuff because it's all sand now.

Thanks for the input.

-greg

[wiwine]

"(...) what I'd really like to do is shift the bias of the cusp across the ripple so it favors one side or the other, so instead of the highest point of the cusp of the ripple always being center ripple, it would maybe closer to the edge of the ripple.  Is this possible?"

Like this ? http://www.planetside.co.uk/forums/index.php/topic,16174.msg158959.html#msg158959

It could be done with a combination of sin functions, to obtain this kind of profile :
[attachimg=1]

On the scheme, wind is coming from the left, so F1 is the windward face, and F2 is the slip (collapsing) face. F2a is for a sand dome profile, F2b is for a dune profile.
Xm is the collapsing point position, 0,72 in that case. It can be changed in the functions.

You will also need a modulo function to repeat the [0->1] values from the coordinates.
Don't know if I'm really clear... perhaps I should write a tutorial...   

[Dune]

It would be best if you put this together in blue nodes in a tgc. That would really be terrific...

[gregtee]

This is exactly the profile I was thinking if.  Most sand ripples I've seen in photographs tend to show a bias as the wind forms them.  Always having the cusp center mass limits the realism in my opinion.  I wish I knew more about the math nodes too Dune, but then again I did manage to figure out how to make the rock formations using them from someone else's assembly of them. 

[Dune]

Math isn't my strongest point either, but I've been fooling around with the blue nodes, so I know a little. By the way, a tilt and shear shader can tilt the sinus ripples somehow as well, but it tilts the whole ground with it.