Re: [brlcad-devel] DSP Questions

[brlcad]

On Jun 05, 2012, at 01:59 PM, Tom Browder <tom.brow...@gmail.com> wrote:

I see there is a skeleton dsp.sh just waiting to be filled in which
I'll happily work on if I can understand the dsp better.

Awesome, I stubbed that in back in shortly after our Coverity work back in January after investigating some DSP issues.  After thinking about all the hole cases possible, I'd come to the conclusion that a 5x5 probably covers most of the topological issues we'll encounter.

 

For instance I'm not sure what the difference between these two are:

# create 1x1 datasets
# ---
# | |
# ---
# and
# ---
# |X|
# ---

I've been assuming a cell is described by the four corners, so it is a
2x2 bitmap with width (X) = 1 and height (Y) = 1.

That's actually a single cell DSP, just one value.  In one configuration, the value is 0.  In the other, it's some non-zero value (say 65536) which should make an arb8/rpp.

>From the example it looks like a single cell has four corners, four
edges, and a center that defines the top surface, but I'm betting the
difference is whether the tops of the four corners (of a 2x2 bitmap)
define a planar quadrilateral or not

And the answer is?

 

DSPs are height-field data implicitly representing geometry.  They are very similar to EBM (http://brlcad.org/wiki/EBM) but instead of simply on/off values for each cell, the cell value represents the height of the cell.

To test it out, you can create a grayscale png image, convert to bw with png-bw, convert to binary unsigned short using the 'cv huc nus' command, and use that datafile for the dsp.  There's an example in the db directory (db/terra.g -- put terra.dsp into your current directory to render) or you can try one of the puget sound data files I linked earlier, or try your hand making your own.

Note that the dsp.sh script can employ a wide variety of ways to make dsp data files similar to how the other scripts make pix reference files. 

Cheers!

Sean

------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
_______________________________________________
BRL-CAD Developer mailing list
brlcad-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/brlcad-devel