Tutorial: Capturing Normal and Displacement Maps
polycounter lvl 18
I've written a tutorial on a method of capturing normal and displacement maps from real objects.
It's easy to do, and requires no special hardware. You just need a camera and a few minutes to spare.
The tutorial is located at http://www.zarria.net
Feedback and comments would be appreciated.
It's easy to do, and requires no special hardware. You just need a camera and a few minutes to spare.
The tutorial is located at http://www.zarria.net
Feedback and comments would be appreciated.
Replies
I have a quickie brain model lying around, that was made procedurally (a 3ds max geosphere, with Noise, Push, and Relax modifiers). Not really a character model, but it's a good way for me to see what happens.
Seems the exe prefers world maps, there's less distortion. But I'm not sure why it has trouble deriving the valleys vs. the hills. Seems like many of the creases are being created as lighter values. I guess that depends on where you start the pixel-walk. I'd love to see more work put into this, if you're willing. This could prove very useful.
Thank you for taking the time to write up the tutorial, and for sharing the exe.
I saw someone do the normal-map-extraction technique with a flatbed scanner about a year or so ago, turning a coin 90 degrees for each scan. He posted examples on the Discreet webboard. Same idea, but with your setup it's a bit easier.
It seems to me you'd get more definition in your normal map if you combined some of the angles into the blue channel, since it seems to help when blue has some variation in it.
Can you talk a bit about how you derive the displacement map? Do you start with the pixel value in one corner and walk across the bitmap, storing the angular changes as darker or lighter values? Do you normalize the heights afterwards?
Here's a similar capture method, getting displacement instead.
http://www.cee.hw.ac.uk/texturelab/projects/virtex/demo/bmpcapture.html
Another method, using stereo pairs.
http://www.virtualclones.com/
Thanks again for your post. Cool stuff!
I saw someone doing that with a flat scanner and a coin on the spiraloid forums too... Great and esy technique
Funny, I tried the exact same thing for normalmaps rendering some weeks ago. I used a little plastic skullas base and it worked surprisingly well...
I guess this is a very good way to build up a texture collection, things like fabric, scales, rocks, aso.
Great tut!
Thanks for giving Displacement Map Creator a test!
Your map confused the software for two reasons:
1. Your green channel (Y-axis) is inverse of what DMC expects. Certain programs bake that way, for some reason. What software did you use to create it?
2. Your black background will confuse DMC; DMC will think the black is a VERY sharp angle on the normal map.
I altered your map to meet DMC's expectation, and here's the result:
Thanks again for testing DMC. Rest assured a new version will soon be forthcoming, with documentation and a control panel.
It's an iterative algorithm. Starting with a flat map, each pixel calculates "flow" from its neighbors, based on each neighbor's slope and current height. All pixels are adjusted very slightly toward their neighbors' expectations, and then the process repeats.
After a few hundred iterations, this yields a pretty good displacement map, which gets normalized to an 8-bit range, and written to disc.
It just did it all in one pass though, which is why it ended up getting about half of the map right before descending into horizontal-streaky-line madness.
I discovered several excellent algorithms for streaky-mess-generation while writing DMC
It seems like DMC is chucking some of the fine detail from the normal map, which is good in this case because the brain one is pretty noisy. I wonder how it works with better source?
It would be helpful if the control panel had an option to choose the Y direction. Our engine is currently setup to expect ATI's Y convention over Nvidia's. I generated the maps with Kaldera, which lets us choose either method.
I found the DMC map had some clipping at the extreme ends of the scale, giving me flat little plateaus and plains. I wonder if this is adjustable?
Thanks again for a great tool. This will be fun to play with some more.
Next version will have y-toggling and backdrop detection. It will also have improvement in capturing detail, possibly involving a user-adjustable slider.
Grab it from www.zarria.net, and please continue to give suggestions. DMC has plenty of room to grow yet.
Here's what V2 does with your brain:
I can't wait to try some of these techniques out!
screenshots:
http://66.70.170.53/Ryan/nrmphoto/crossrenders3.jpg
http://66.70.170.53/Ryan/nrmphoto/crossrenders%20copy.jpg
http://66.70.170.53/Ryan/nrmphoto/crossrenders%20copy2.jpg
captured maps:
http://66.70.170.53/Ryan/nrmphoto/crossColor.jpg
http://66.70.170.53/Ryan/nrmphoto/crossnrm.jpg
http://66.70.170.53/Ryan/nrmphoto/cross_DISPLACEMENT.jpg
I'd love to take advantage of a technique like this, but lighting from four different directions would make tiling a pain.
Any steps on this?
Best way I've found is to capture the normal map first, then modify it for tiling with the clone brush.
You can record the tiling of your color map, and play back the same action on your normal map. A highpass filter before tiling is often helpful.
I've posted actions that flip and rotate normal maps while transforming the normals to compensate. They make it easy to tile-by-mirroring, at least.
DMC does take tiling to account. So if your normal map tiles, your displacement map will also tile.
I've posted actions that flip and rotate normal maps while transforming the normals to compensate. They make it easy to tile-by-mirroring, at least.
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What exactly do you mean? Is that like the high-pass filter method where you chop the image into like 4 sections and move them around, patch the seems and that sort of thing.
I've seen it at cokane.com? Chris O'Kane? His website.
The difference here is that you must apply the same steps to both color map and normal map.
One difficulty is that "flip" and "rotate" commands can't be used on a Normal Map. Orientation is important with normals; if you change orientation, you need to change color accordingly. For example, a vertical flip must be followed by inversion of the green channel. The actions on my site let you flip or rotate the normal map in a single step.
so, your workflow would look something like this:
1. Open your color map, and begin recording a new action.
2. Tile your color map, follwing the example of Conor O'Kane's tutorial.
3. Stop recording your action.
4. Look through the steps of your action, and replace each "flip" or "rotate" command with the corresponding action from my set.
5. Open your normal map, and playback your modified tile-making steps.
Matt Vainio's Texturing Tutorial
http://www.twisted-strand.com/ut_tutorials/text_tut/index.html
Peter Hajba's Power of the High Pass Filter
http://www.3dgate.com/techniques/2001/010625/0625hajba.html
Jeremy Birn's Fixing Lighting Irregulaties in Self-Tiling Maps
http://www.3drender.com/light/EqTutorial/tiling.htm
All of this normal map / displacement map stuff doesn't seem natural to me as an artist. It all makes sense, but is damn hard to apply correctly when the artist in me takes over. I am sure that is because I haven't played around with it much, and or it is so new they haven't made it WYSIWYG enough for me yet. Believe it or not, this does help quite a bit, and is a brilliant idea, I just can't really use it that well for the kind of textures I am working on right now. I will squirl this one away for a rainy day
But this might help.
http://www.jeffparrott.com/normalmaptut_01.html