algorithm - Structured Light - How to do when the projector's resolution is lower than patterns? -

i try build structured light environment 3d scanning.

as far know, if choose use gray code reconstruct 3d model, have implement specific patterns encode in power 2(2^x, x = 0 ~ 10).

that said, patterns must @ least 1024 x 1024 in resolution.

what if dlp projector support resolution 800 x 480? projects moire pattern when gray code pattern resolution becomes high(i tried). should do?

my friends suggest create 1024 x 1024 patterns, , "crop" them 800 x 480,

but thought gray code should follow specific sequence , patterns, friends suggestion create several image not symmetry.

does have same experience me?

----------2015.8.4 update question----------

i thinking if projector can't projects high resolution patterns, can let projects patterns low resolution, instance, 2^0 2^6?

or gray code strictly demands patterns 2^0 2^10? otherwise gray code not available?

you can not directly scale down resolution

because distort pattern make useless

instead can:

1. crop resolution

   but need handle in scanning part because not have full pattern available

2. use nearest usable power of 2 resolution

   like 512x256 , create pattern it. rest of space unused (wasting pixels)

3. use bullet #2 + scale fit resolution better

   so create pattern 512x256 , linearly scale fit 800x480 as can so:

   800/512 = 1.5625 480/256 = 1.8750 

   use smaller scale (512x256 * 1.5625 -> 800x400) scale pattern 1.5625 , use pattern image

   

   this scaled nearest neighbor avoid subpixel grayscale colors harder detect. this waste less pixels can lower precision of 3d scan !!!

this how generate pattern in c++ , vcl:

// [generate pattern xs*ys power of 2 resolution] // clear buffer bmp->canvas->brush->color=clblack; bmp->canvas->fillrect(trect(0,0,xs,ys)); int x,y,a,da; (da=0;1<<da<xs;da++);                   // number of bits per x resolution (a=0,y=0;y<ys;y++,a=(y*da)/ys)  (x=0;x<xs;x++)   if (int((x>>a)&1)==0) pyx[ys-1-y][x]=0x00ffffff; bmp->savetofile("3d_scann_pattern0.bmp"); 

• bmp vcl bitmap
• xs,ys resolution of bitmap
• p[ys][xs] direct 32bit pixel access bitmap

this slight differently encoded pattern !!!

[notes]

• if need precision use bullet #2
• if need cover bigger area use bullet #3
• you can scale in y axis differently in x axis 1d encoding