Simple 3d - the normal map

[jseiler]

I've been playing around with normal mapping. This is commonly used in the game programming world, but I haven't seen anyone using it for generating reliefs for cnc machining.

Info about normal mapping from wikipedia:
http://en.wikipedia.org/wiki/Normal_mapping

Using software such as crazy bump (free in beta for a limited time), one can quickly convert a normal map into a displacement map (a relief much like a lithophane). One can also convert a properly lighted image into a normal map then to 3d! (working on a tutorial for this).

http://www.crazybump.com/

Crazy bump will also take an image that's even lighted and generate a normal map from it. Evenly lighted is most easily achieved by taking a picture of the item on an overcast day.

If you want to play with this software and technique, here is a cool normal map you can start with:

Normal map of the world:
http://celestia.h-schmidt.net/earth-vt/normal1024.jpg

Fire up crazy bump, load the image above as a normal map, and let it generate a displacement map. Saving the displacement map yields a gray scale picture with white in the picture being the highest, and black the lowest, kind of like a lithophane. Load it into software that cuts lithophanes. I use my own software I wrote in matlab, but you could use anything that will scale and cut a lithophane.

If you wish to make your own normal maps, here is a tutorial using a camera, light source and photoshop. I don't have photoshop and I am trying to work this out using gimp (free).

Making your own normal maps:
http://zarria.net/nrmphoto/nrmphoto.html

If you search on google images using "normal map" as a search term, you can find hundreds of these, some of them are really cool. That's where I found the earth map.

have fun,
John

[henrik_o]

We talked about this in the chat, the whole concept is very interesting.

I hope to get some time this weekend to try out the approach in your last link.

John, have you machined anything from a normal map?

[jseiler]

cutting this one as I type.

Normal map (reduced in resolution to fit here):

http://ps3media.ign.com/ps3/image/article/730/730230/untold-legends-dark-kingdom-20060901020202744.jpg


6575

Displacement map from crazy bump:

6576

I'm cutting a 5" square in maple, using .3" of total z height. I'll post a pic later...so far, so good.

John

[jseiler]

Here's the carved version, hot off the machine. I'll stain it later, so you can see the detail.


6577

1/8" ballnose, 10% stepover, .3" total depth. 5" square.

I just need a better way to get accurate normal maps from photos. Still working on that.


John

[jseiler]

here's the stained version in dark oak, no clear coat yet. Its a lot better than this lo-res shot (and my bad spray staining) can show.


6578

John

[jseiler]

After a couple of emails, perhaps a couple of things need clarification. As far as I know, this method won't give a completely accurate 3d model like cad or other 3d programming might. What it will do is give one the ability to do what game programmers and movie makers have been doing for some time...taking texture from nature, pictures or your imagination and applying it over a surface. In this case, we're not making an accurate texture rendering of the deathstar, we're creating realistic texture for CNC cutting. Some of these textures can be quite detailed, as one can see above.

Instead of thinking about digitizing ferraris, think about sign backgrounds, replicating wood grain, brick, firespray, sandblasting, stucco, mortar, or even as above, something that looks like worn antique carving.

If someone has experience in photography to convert to detailed normal maps, I'd love to hear about how one gets really awesome results. Is it all in the lighting or is there some other magic?

May be its my crummy camera.


John
"and how come the forum software censors may-be (spelled as one word)?"

[joe]

John,

Is your concern the quality of photo's and or their enhacement?

[jseiler]

For simple textures, overcast day pix and fiddling around in crazybump controls seems to work just great and anyone can get completely usable background texture in about 15 minutes after getting acclimated to the crazybump software.

However....

Looking at the website highlighted in the first post on generating normal maps:

http://zarria.net/nrmphoto/nrmphoto.html

Check out the carving at the bottom of the page. Holy cow, its spectacular, even, dimensionally accurate, with very even lights and darks in all quadants, necessary for cutting a depth accurate copy.

I've tried replicating his 4 picture process and my displacement map ends up not nearly as even. Where the depths should be exactly the same, they appear as different shades of grey, which cuts to a "warped" relief.

I've not tried tightly controlling the incident angle of the lighting. Or perhaps the owner of the website is cheating a bit and tweaking the snot out of his heightmaps. Dunno yet.

John

[joe]

John,

I believe photo masking enhancement in Photoshop, where light and shadows can be moved and controlled would be a shortcut to taking four pix.

Have you looked into these techniques?

Joe

[jseiler]

I use gimp, because photoshop isn't in my budget right now. There's another branch of GIMP called GIMPSHOP that I haven't had time to explore that might have those filters in place.

Last night, I carefully looked at that websites lighting and think if I improved my lighting, I might get further. I was using a flashlight and looking carefully at my shots, I may have had hotspots and areas on the edges of the light cone that were not illuminated evenly.

Another 3d note of interest is this thread on the vectric website:

http://www.vectric.com/forum/viewtopic.php?t=1955&highlight=

I've bought Yohudi's guide, but haven't had time to delve into it yet. Its is a pretty nice guide for getting 2.5d out of clipart quickly using available "public domain" software, namely Gmax and some scripts that Yohudi wrote.

John