[GRASS-user] general v.digit help? Enduring thanks

[hardinej]

Hello,
Thanks to anyone who can help. I usually work with raster data, but I've been venturing into the world of vector data because I can make good masks. What I've been doing is using r.contour to extract a shoreline on a beach, and then I've been digitizing an almost rectangular area using v.digit where one side of the rectangle is the extracted shoreline. Then I convert that area to a mask and perform raster operations from there. r.digit is a poor sub for v.digit with a derived shoreline in my case.
So, some of the literature seems a little sparse, so I've been using a lot of trial and error unfortunately.
Here is my work flow,
I open the contour line in v.digit and connect the ends to make a boundary. I add a centroid to make it an official area. I make sure all of the nodes are green. I don't really know why, it just works that way. So that would be my first question, what is the difference between green and red nodes/vertices? I do this by using the split lines tool and essentially cutting out red nodes and reconnecting the lines until they turn green. Again, I'm having a little bit of trouble interpreting what yellow lines mean when using the split line tool.  
Then, (once again because it just seems to work, sometimes) I use v.type input=vec1 output=vec2 type=line,boundary followed by
v.to.rast input=vec2 output=vec3 use=val type=point,line,area layer=1 value=1 rows=4096. And sometimes it works and sometimes it doesn't, but I don't know why. Also, when converting between vector types using v.type, I notice the output will say something like:
Number of nodes     :   12
Number of primitives:   16
Number of points    :   0
Number of lines     :   0
Number of boundaries:   15
Number of centroids :   1
Number of areas     :   0
Number of isles     :   0
Number of incorrect boundaries   :   15
Number of centroids outside area :   1
I have difficulties trouble shooting the problem from this output.
So, I've tried to read man pages and work my way through tutorials to no avail. If anyone knows the answer to these questions, or knows of a tutorial or resource that can help me, I will be eternally grateful.
Thanks,
Eric 
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