[GRASS-user] displaying volumes from xyz vector in nviz

[ian summers]

My data is indeed a point cloud from bathymetry data so I can understand the problems you outlined so I will be happy to create 3d output from the multiple slicing method of r.to.rast3. I have only previously set a 2d region which all points lie within but am unsure how to set a 3d region?  I 'successfully' ran the v.vol.rst command with my DOC data by specifying the w column as you suggested though it turns out the data is not sufficient in terms of density and it does in fact say points are outside 2d/3d region. Apologies for all these questions.  I am still new to GRASS.  > Date: Thu, 21 Aug 2008 12:37:40 +0100> From: benjamin.ducke at oxfordarch.co.uk> To: i.summers at hotmail.co.uk> Subject: Re: [GRASS-user] displaying volumes from xyz vector in nviz> > If what you are after is the actual shape of the loch in voxel space:> that is not easy to do with current GRASS tools.> I do not know what your input data looks like, but I assume it is a> point cloud derived from bathymetry data? If so, then what you have> is a cloud of point describing the exterior hull of the loch. In order> to convert this to a voxel object, GRASS would need to be able to first> construct the polygonal hull using these points and then convert that> to a voxel representation. This is not currently possible and would> require someone to put some serious effort into creating a module> with the capability to convert 3D vector polygons to volumetric voxel> representations.> > I have never heard about the 'position not in queue' message. No idea> what is going wrong there.> > v.vol.rst should work fine if you use the 'wcolumn=' option to specify> the name of the attribute you want to interpolate.> > Have you set the 3D region extents correctly to cover your 3D input> data and produce the number of slices you want?> > Ben> > ian summers wrote:> > Hello Ben,> > > > Thank you for your suggestion but when I attempt to run r,to.rast3 I get > > the 'position not in queue' message again. I ran v.kernel on the > > respective slices with st deviation of 5 leaving all other parameters as > > they were. Was this correct? Having used the v.info command the layers > > are 3D. Essentially what I am trying to achieve is a volume cube of loch > > lomond from x, y, z coordinates. > > > > I also have dissolved organic carbon data which i was hoping to display > > volumetrically within this that has x, y, z, DOC columns. I ran > > v.vol.rst but it says w column not supported. my data here is:-> > > > INTEGER/cat> > > > > INTEGER/Id> > > > > DOUBLE PRECISION/X> > > > > DOUBLE PRECISION/Y> > > > > DOUBLE PRECISION/Z> > > > > DOUBLE PRECISION/DOC> > > > My main focus is the volume cube of loch lomond. The DOC would be a bonus.> > > > Ian> > > > > Date: Thu, 21 Aug 2008 09:55:07 +0100> > > From: benjamin.ducke at oxfordarch.co.uk> > > CC: grass-user at lists.osgeo.org> > > Subject: Re: [GRASS-user] displaying volumes from xyz vector in nviz> > >> > > To generate a volumetric model of your point data, you need to use> > > an algorithm that can interpolate an attribute in 3D space.> > >> > > To start with, you need to make sure that your input points map is> > > actually a 3D geometry, not just 2D points with X,Y and Z attributes> > > attached (us v.info to find out).> > >> > > v.to.rast3 simply takes the 3D point positions and creates a single> > > voxel value at every point location in the input map. Most likely, this> > > is not what you want and you should look into v.vol.rst instead.> > >> > > The question then is WHAT to interpolate. In your attribute table list> > > below, I cannot see an attribute that could actually be used for> > > interpolation. The only thing you have are integer categories.> > >> > > If you want to show point density in 3D: there is currently no GRASS> > > module to calculate that. So the only thing you can do is calculate> > > density for 2D slices at different Z ranges separately (use v.select> > > to query out points for each Z range, then run v.kernel on them) and> > > stack the resulting 2D raster maps on top of each other to form a voxel> > > cube using r.to.rast3.> > >> > > Ben> > >> > >> > > ian summers wrote:> > > > Dear all,> > > >> > > > I have a vector point file and have tried to run the program > > v.to.rast3> > > > though in the 'column name' section I am unsure what to enter? the> > > > column attributes for the data are as follows.> > > >> > > > > INTEGER/cat> > > > > INTEGER/Id> > > > > DOUBLE PRECISION/X> > > > > DOUBLE PRECISION/Y> > > > > DOUBLE PRECISION/Z> > > >> > > > I have tried entering cat, id and z in this box but in the output I> > > > receive the message 'position not in queue'.> > > >> > > > I have also tried to create the volume using r.to.rast3 and though it> > > > appears as though a file is created when it comes to display in nviz> > > > only a plain 2D white tile appears. The values in my Z column are> > > > negative as I am modelling a lake. I am unsure whether this holds any> > > > bearing on outcome.> > > >> > > > Hope someone can help.> > > >> > > > Ian Summers> > > >> > > >> > > > > > ------------------------------------------------------------------------> > > > Win £3000 to spend on whatever you want at Uni! Click here to WIN!> > > > <http://clk.atdmt.com/UKM/go/101719803/direct/01/>> > > >> > > >> > > > > > ------------------------------------------------------------------------> > > >> > > > _______________________________________________> > > > grass-user mailing list> > > > grass-user at lists.osgeo.org> > > > http://lists.osgeo.org/mailman/listinfo/grass-user> > >> > >> > > --> > > Benjamin Ducke> > > Senior Applications Support and Development Officer> > >> > > Oxford Archaeology Ltd> > > Janus House> > > Osney Mead> > > OX2 0ES> > > Oxford, U.K.> > >> > > Tel: +44 (0)1865 263 800 (switchboard)> > > Tel: +44 (0)1865 980 758 (direct)> > > Fax :+44 (0)1865 793 496> > > benjamin.ducke at oxfordarch.co.uk> > >> > >> > >> > >> > > ------> > > Files attached to this email may be in ISO 26300 format (OASIS Open > > Document Format). If you have difficulty opening them, please visit > > http://iso26300.info for more information.> > >> > > _______________________________________________> > > grass-user mailing list> > > grass-user at lists.osgeo.org> > > http://lists.osgeo.org/mailman/listinfo/grass-user> > > > > > ------------------------------------------------------------------------> > Find out how to make Messenger your very own TV! Try it Now! > > <http://clk.atdmt.com/UKM/go/101719648/direct/01/>> > > -- > Benjamin Ducke> Senior Applications Support and Development Officer> > Oxford Archaeology Ltd> Janus House> Osney Mead> OX2 0ES> Oxford, U.K.> > Tel: +44 (0)1865 263 800 (switchboard)> Tel: +44 (0)1865 980 758 (direct)> Fax :+44 (0)1865 793 496> benjamin.ducke at oxfordarch.co.uk> > > > > ------> Files attached to this email may be in ISO 26300 format (OASIS Open Document Format). If you have difficulty opening them, please visit http://iso26300.info for more information.> 
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