Add Blender tut

documentation/utilities/gmtread.md

@@ -13,8 +13,8 @@ the chance of letting the data type be guessed via the file extension. Known ext
 
 - Grids:      .grd, .jp2 .nc
 - Images:     .jpg, .jp2 .png, .tif, .tiff, .bmp, .webp
-- Datasets:   .dat, .txt, .csv
-- Datasets:   .shp, .kml, .json, .geojson, .gmt, .gpkg, .gpx, .gml (or *.zip.ext)
+- Datasets:   .dat, .txt, .csv, .isf
+- Datasets:   .arrow .arrows .shp .kml .kmz .json .gmt .feather .fgb .gpkg .geojson .gpx .gml .ipc .parquet .sqlite (or *.ext.zip)
 - CPT:        .cpt
 - PostScript: .ps, .eps
 
@@ -43,6 +43,8 @@ Specify data type (with *type*=true, e.g. `img=true`). Choose among:
   (the one with `gdal`) uses GDAL to read the cube and outputs and 3D array in row major order.
   Remember that the ``layout`` member of the GMTgrid type informs about memory layout.
 
+- `inrows`: Select specific data rows to be read. Valid args include ranges or a string with an hard core GMT -q option.
+
 - `stride`: When reading table data via GMT (but not GDAL), this option allows subsampling the data.
   Provide a number to be used as stride for the rows. A `stride=2` will read every other row.
 

tutorials.md

@@ -89,6 +89,17 @@
     ~~~</a>~~~
   @@
 
+  @@box
+    ~~~<a class="boxlink" href="blender_shading/blender_rt/">~~~
+    @@title Raytrace shading@@
+    @@box-content
+      ~~~
+      <img src="/tutorials/blender_shading/tilelogo.jpg">
+      ~~~
+    @@
+    ~~~</a>~~~
+  @@
+
   @@box
     ~~~<a class="boxlink" href="mosaics/mosaics/">~~~
     @@title Images mosaic@@

tutorials/blender_shading.md

@@ -0,0 +1,3 @@
+# Shading with Blender
+
+{{list_folder_with_images blender_shading}}

tutorials/blender_shading/blender_rt.md

@@ -0,0 +1,66 @@
+# Shading with Blender
+
+This tutorial shows how we can create stunning shaded relief images using the Blender ray tracer to solve
+the hard jobb of computing illumination with realist shadows of a DEM surface. The tutorial linked bellow
+takes some time to follow and the time needed to compute the raytraced image is on the order of minutes.
+However, as the author says at the end, once we have it set for one case it is easy and fast to adapt it
+to other cases. In a posterior improvement of this tutorial we will show how to modify needed parameters
+of the _.blend_ file that is run by Blender to create the raytraced image.
+
+
+\begin{examplefig}{}
+```julia
+using GMT
+
+# Extract a region of West Ibaria from the 15 arc sec grids stored in the GMT server
+Gwib = grdcut("@earth_relief_15s", region=(-10.5, -5, 35, 44));
+
+# Create a tint image from the Gwib grid
+I = grdimage(Gwib, C=:earth, img_out=true);
+viz(I, coast=true)
+```
+\end{examplefig}
+
+Load the previously created raytrace image computed with Blender following the tutorial
+[Creating Shaded Relief in Blender](https://somethingaboutmaps.wordpress.com/2017/11/16/creating-shaded-relief-in-blender/)
+But note that the first part of that tutorial where it explains how to cretae the UInt16 _heightmap_ can be replaced by
+this simple command:
+
+\begin{examplefig}{}
+```julia
+using GMT
+
+gdalwrite("Gwib.tiff", rescale(Gwib, type=UInt16))
+```
+\end{examplefig}
+
+Load the gray scale image and show it:
+
+\begin{examplefig}{}
+```julia
+using GMT
+
+Iblend = gmtread("https://oceania.generic-mapping-tools.org/cache/wiberia_shade_blender.png");
+viz(Iblend, coast=true)
+```
+\end{examplefig}
+
+Now apply the techniques explained in this tutorial [Adding Shaded Relief in Photoshop](https://somethingaboutmaps.wordpress.com/2014/10/26/adding-shaded-relief-in-photoshop/)
+to blend the tint, the shades and illumination
+
+
+\begin{examplefig}{}
+```julia
+using GMT
+
+I = grdimage(Gwib, C=:earth, img_out=true);		# Hide
+Iblend = gmtread("https://oceania.generic-mapping-tools.org/cache/wiberia_shade_blender.png");	# Hide
+# Blend the tint and the shades (darken)
+Iburn = blendimg!(I, Iblend, mode="LinearBurn", new=true);
+
+# Apply illunination to the previous image
+Ib = blendimg!(Iburn, Iblend, mode="Screen", new=true);
+
+viz(Ib, coast=true)
+```
+\end{examplefig}