Racetrack Playa

[schmeerlap]

Inspired by Bob's (choronr) comments accompanying his Rock Enigma, I thought I'd try and replicate the Racetrack Playa in Death Valley and its Gliding Stones. You can check out actual pics at Wickiepedia.

John

[matrix2003]

Looks like National Geographic John!

[cyphyr]

Excelent, but um... is there just a little photoshop trickery going on ?
Richard

[Saurav]

Great reconstruction of the scene.

[Mr_Lamppost]

Ouch the pattern of mud cracks is way too even; they're all lined up in rows.  Otherwise quite convincing.

[schmeerlap]

@ cyphyr:

... is there just a little photoshop trickery going on ?

The cracked clay pattern was created using Photoshop and used as an image map in Terragen. The boulder trail groove is defined using an image mask which was created in Photoshop. Photoshop was also used to enhance colour definition. Standard input and output procedures used by many other Terrageners as I understand it. Trickery?
@ Mr_Lamppost:

Ouch the pattern of mud cracks is way too even; they're all lined up in rows.

Cracked clay segments tend to be roughly the same size and if you look closely at a photo of them at a shallow pov the eye will quite naturally begin see repeating patterns. The foreground (where the pattern is most clearly defined) is not repetitive to my eye, but the eye quite naturally begins to see repetition at a distance. What do you think (nice try at a convincing argument, or utter bull****)? The Photoshop image I created was 2048x2048 with approx 40x40 cracked clay cells; constructed by using the cloud filter, then a layer using stained glass filter, then making the cell borders irregular using the glass distortion filter, and then adding some grain for roughage.

John

[schmeerlap]

Here's a couple of pics of the actual Racetrack Playa (Death Valley). The clay cells here are quite regular with similar sized cells, and the eye (as is its wont) does seek out patterns. Having said that, I do admit that my scene is too symetrical in its rendition of the clay cells and they could be more rounded in shape. Mr_Lamppost is quite right to point this out, although "all lined up in rows" is a wee bit of an exageration.

John

[cyphyr]

@ cyphyr:

... is there just a little photoshop trickery going on ?

The cracked clay pattern was created using Photoshop and used as an image map in Terragen. The boulder trail groove is defined using an image mask which was created in Photoshop. Photoshop was also used to enhance colour definition. Standard input and output procedures used by many other Terrageners as I understand it. Trickery?

No trickery then
I think I was seeing some jpg artifaction on the two foreground stone edges, looked like two images overlayed (a perfectly reasonable technique I might add).
richard

[schmeerlap]

Well spotted, Richard. I did indeed do a second crop render of the bottom half of the scene (the flats) as I wasn't happy with the original. And I did overlay that in Photoshop. Actually this scene had such a quick render time it would have been just as easy to re-render the lot. Might still do that if I think its worth it. Itching to move on, though.

John

[rcallicotte]

Fine work.  Never remember hearing of this racetrack before today.

[Mr_Lamppost]

@ Mr_Lamppost:

Ouch the pattern of mud cracks is way too even; they're all lined up in rows.

Cracked clay segments tend to be roughly the same size and if you look closely at a photo of them at a shallow pov the eye will quite naturally begin see repeating patterns. The foreground (where the pattern is most clearly defined) is not repetitive to my eye, but the eye quite naturally begins to see repetition at a distance. What do you think (nice try at a convincing argument, or utter bull****)? The Photoshop image I created was 2048x2048 with approx 40x40 cracked clay cells; constructed by using the cloud filter, then a layer using stained glass filter, then making the cell borders irregular using the glass distortion filter, and then adding some grain for roughage.

John

I thought as much, I've used that filter before and don't even think it makes good stained glass.  There is just not enough randomness in it.

Some very good mud cracks with a far more natural distribution can be created from Voronoi noise via the use of function nodes.  I am sure that examples have been published before but can I find them?  I gave up and created this.  It's a bit rough, the render took longer than creating the network. 

Theer are a bunch of function nodes (Scary blue boxes) that plug into a displacement shader in the same way as you would use an image map.  I have given the important nodes what I hope are meaningful names.  The complete scene that creates the example image is included along with a clip file containing just the displacement shader and the functions to create the cracks. 

Hope this is of interest and or help.

[Esgalachoir]

How old are those pictures?  I seem to remember them from ages ago.

[Esgalachoir]

Nice job by the way!

[schmeerlap]

@ Esgalachoir: I found the two pics at Flickr: the first was uploaded in Feb 08 by Sandman, and the second in Nov07 by Colforbin88. I didn't add credits as I used them only for illustrative purposes.

John

[schmeerlap]

Thanks Mr_Lamppost. You did go to a lot of trouble and your effort is much appreciated. I'll download your clip and tgd files, and study and learn from them. Let me just say that the result is more akin to the normal cracked clay one finds on dried up lake and river beds. The Racetrack Playa cells (as I call them) are more pudding shaped; ie are more round than straight-edged polygons. I'll have one more effort with an image map which I will make by hand (so to speak) in Photoshop using a custom paintbrush, in order to acheive a more random distribution. Thanks again for the node and function knowledge you've imparted. One day I'm going to get my numpty-like head round these function node network thingies.

John