3D unstructured Grid

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3D unstructured Grid

Francois Chartier
Hi, 

Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

thanks

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Re: 3D unstructured Grid

Carlos Henrique Grohmann de Carvalho-2
What do you mean? Like a 3D mesh? 
You can use Meshlab, ClouCompare or Paraview to do that, and then exporting it back to GRASS as 3D faces.

C

On Sat, Sep 29, 2018 at 5:44 PM, Francois Chartier <[hidden email]> wrote:
Hi, 

Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

thanks

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Institute of Energy and Environment - Univ. of São Paulo, Brazil
- Digital Terrain Analysis | GIS | Remote Sensing - 

http://orcid.org/0000-0001-5073-5572
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Re: 3D unstructured Grid

wenzeslaus
In reply to this post by Francois Chartier
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav

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Re: 3D unstructured Grid

Saber Razmjooei
Hi,

Sorry to hijack the discussion related to GRASS. But, we are working a new library to handle mesh data. MDAL is currently supported in QGIS. But the idea is to make it generic so other OS GIS application can handle the mesh layer through a generic library similar to GDAL. Here is more info about MDAL:

You can find some example of the formats supported there too.

Regards
Saber
 

On Tue, 2 Oct 2018 at 03:01, Vaclav Petras <[hidden email]> wrote:
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav
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Re: 3D unstructured Grid

Carlos Henrique Grohmann de Carvalho-2
That seems very interesting! Any plans to support PLY?

Carlos

On Tue, Oct 2, 2018 at 9:32 AM, Saber Razmjooei <[hidden email]> wrote:
Hi,

Sorry to hijack the discussion related to GRASS. But, we are working a new library to handle mesh data. MDAL is currently supported in QGIS. But the idea is to make it generic so other OS GIS application can handle the mesh layer through a generic library similar to GDAL. Here is more info about MDAL:

You can find some example of the formats supported there too.

Regards
Saber
 

On Tue, 2 Oct 2018 at 03:01, Vaclav Petras <[hidden email]> wrote:
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav
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Saber Razmjooei
www.lutraconsulting.co.uk
+44 (0)7568 129733

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--
Prof. Carlos Henrique Grohmann
Institute of Energy and Environment - Univ. of São Paulo, Brazil
- Digital Terrain Analysis | GIS | Remote Sensing - 

http://orcid.org/0000-0001-5073-5572
________________
Can’t stop the signal.

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Re: 3D unstructured Grid

Saber Razmjooei
The purpose of MDAL is slightly different from 3D meshes such as PLY. In 3D mesh, you store just elevation (either face or corners) and some type of materials. But in MDAL, the aim is to store quantities on top of the mesh (e.g. a mesh for ground elevation and water depth on top over a period of time). So in essence, it is more like 2.5D  (+time). 

Cheers
Saber

On Tue, 2 Oct 2018 at 13:40, Carlos Henrique Grohmann de Carvalho <[hidden email]> wrote:
That seems very interesting! Any plans to support PLY?

Carlos

On Tue, Oct 2, 2018 at 9:32 AM, Saber Razmjooei <[hidden email]> wrote:
Hi,

Sorry to hijack the discussion related to GRASS. But, we are working a new library to handle mesh data. MDAL is currently supported in QGIS. But the idea is to make it generic so other OS GIS application can handle the mesh layer through a generic library similar to GDAL. Here is more info about MDAL:

You can find some example of the formats supported there too.

Regards
Saber
 

On Tue, 2 Oct 2018 at 03:01, Vaclav Petras <[hidden email]> wrote:
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav
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--
Saber Razmjooei
www.lutraconsulting.co.uk
+44 (0)7568 129733

_______________________________________________
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--
Prof. Carlos Henrique Grohmann
Institute of Energy and Environment - Univ. of São Paulo, Brazil
- Digital Terrain Analysis | GIS | Remote Sensing - 

http://orcid.org/0000-0001-5073-5572
________________
Can’t stop the signal.


--
Saber Razmjooei
www.lutraconsulting.co.uk
+44 (0)7568 129733

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Re: 3D unstructured Grid

Francois Chartier
In reply to this post by wenzeslaus
Amazing!  If you data represents a property (K) that is given for the top elevation (Z) at which it is identified in the database. 
With v.vol.rst, are you able to assign that property downwards until the next property value.  
For example, in the example on the webpage, there is a 3D raster for soil moisture; if the soil moisture is measured only for the top of a cylinder along your vertical hole, the next moisture measurement is taken at a lower depth, and the intervals (cylinder length) are not the same along that vertical axis?

Le lun. 1 oct. 2018 à 22:01, Vaclav Petras <[hidden email]> a écrit :
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav

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Re: 3D unstructured Grid

wenzeslaus


On Tue, Oct 2, 2018 at 9:38 PM Francois Chartier <[hidden email]> wrote:
For example, in the example on the webpage, there is a 3D raster for soil moisture; if the soil moisture is measured only for the top of a cylinder along your vertical hole, the next moisture measurement is taken at a lower depth, and the intervals (cylinder length) are not the same along that vertical axis?


Yes, all are (can be) different. The values are interpolated in between. The input are arbitrary places points. The output is a regular grid. Note, you may need to explore zscale parameter of v.vol.rst because of the how your data looks like.

 

Le lun. 1 oct. 2018 à 22:01, Vaclav Petras <[hidden email]> a écrit :
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav

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Re: 3D unstructured Grid

Francois Chartier
Hi Vaclav, 

Question:
1-can the value remain constant until the next underlying data point?  
2-by "the output is a regular grid"  does that mean that the points (vector) can be unstructured, but in the end the raster or mesh is a regular grid?  if that is the case, how does the value in the raster determined? Is it an interpolated value between the points that fall with in the raster cell footprint?

thanks,
Francois

Le jeu. 4 oct. 2018 à 22:48, Vaclav Petras <[hidden email]> a écrit :


On Tue, Oct 2, 2018 at 9:38 PM Francois Chartier <[hidden email]> wrote:
For example, in the example on the webpage, there is a 3D raster for soil moisture; if the soil moisture is measured only for the top of a cylinder along your vertical hole, the next moisture measurement is taken at a lower depth, and the intervals (cylinder length) are not the same along that vertical axis?


Yes, all are (can be) different. The values are interpolated in between. The input are arbitrary places points. The output is a regular grid. Note, you may need to explore zscale parameter of v.vol.rst because of the how your data looks like.

 

Le lun. 1 oct. 2018 à 22:01, Vaclav Petras <[hidden email]> a écrit :
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav

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Re: 3D unstructured Grid

Francois Chartier
In reply to this post by wenzeslaus
Hi Vaclav, 

other questions: 
how many data points did you use, and 
how many grid cells in the 3d grid ?



Le lun. 1 oct. 2018 à 22:01, Vaclav Petras <[hidden email]> a écrit :
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav

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Re: 3D unstructured Grid

wenzeslaus
In reply to this post by Francois Chartier


On Wed, Oct 10, 2018 at 8:34 PM Francois Chartier <[hidden email]> wrote:
Hi Vaclav, 

Question:
1-can the value remain constant until the next underlying data point?  

v.vol.rst is for interpolation, but a constant value can be achieved with r.to.rast3elev or r.to.rast3, but I think in your case you will likely need some prereprocessing to get the right rasters from your irregular points.


I think there was some addon or script for working with soil types (which is how your case sounds). Perhaps somebody knows more about it.
 
2-by "the output is a regular grid"  does that mean that the points (vector) can be unstructured, but in the end the raster or mesh is a regular grid?

Yes, 3D points (XYZ tuples) and (regular) 3D raster (grid).
 
  if that is the case, how does the value in the raster determined?

v.vol.rst is interpolating the value using "regularized spline with tension" aka RST, i.e. it is applicable to properties which are a real number, but it is not suitable for categorical data.
 
Is it an interpolated value between the points that fall with in the raster cell footprint?

The interpolation happens for the raster cells (or you can think of them as grid locations in the middle of the raster cell). Usually, there would be much more raster cells than vector points, but the RST interpolation works the same way in all cases.

 

thanks,
Francois

Le jeu. 4 oct. 2018 à 22:48, Vaclav Petras <[hidden email]> a écrit :


On Tue, Oct 2, 2018 at 9:38 PM Francois Chartier <[hidden email]> wrote:
For example, in the example on the webpage, there is a 3D raster for soil moisture; if the soil moisture is measured only for the top of a cylinder along your vertical hole, the next moisture measurement is taken at a lower depth, and the intervals (cylinder length) are not the same along that vertical axis?


Yes, all are (can be) different. The values are interpolated in between. The input are arbitrary places points. The output is a regular grid. Note, you may need to explore zscale parameter of v.vol.rst because of the how your data looks like.

 

Le lun. 1 oct. 2018 à 22:01, Vaclav Petras <[hidden email]> a écrit :
On Sat, Sep 29, 2018 at 4:45 PM Francois Chartier <[hidden email]> wrote:
Can Grass GIS create a 3D unstructured grid based on a 3D point data set ?

All data and visualizations at the following website were created in GRASS GIS including a 3D regular grid (3D raster in GRASS GIS) interpolated from a set of 3D points (vector which is 3D, i.e. with z, in GRASS GIS). Points were soil properties measurement at different depths, 3D raster is then continuous representation of a selected property.


Module used for interpolation was v.vol.rst:


Vaclav

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