Gnuplot: Respect depthorder for Gnuplot 3d polygons
<p>I have a 3D model of a complete city, and would like to show an
isometric view of those buildings. I use gnuplot polygons for this,
since I don't think I can use pm3d for polygons with coordinates that
aren't on a well defined grid. The polygons are displayed with a color
corresponding to the average amount of solar irradiance they get. I
also display the ground polygons as wireframe, mostly to set xrange,
yrange and zrange automatically.</p>

<p>It looks okay from far away, but when you zoom in, you see that the
depthorder of some polygons are wrong.</p>

<p>This is the CityGML model imported into SketchUp :
<a href="https://i.stack.imgur.com/8Ypps.png" rel="noreferrer"><img src="https://i.stack.imgur.com/8Ypps.png" alt="enter image description here"></a></p>

<p>This is what comes out of Gnuplot :
<a href="https://i.stack.imgur.com/AQZMG.png" rel="noreferrer"><img src="https://i.stack.imgur.com/AQZMG.png" alt="enter image description here"></a></p>

<p>Do you have any idea how I could display those polygons in the right order?</p>

<p>Something like <a href="http://www.gnuplotting.org/tag/depthorder/" rel="noreferrer">this</a> would be great, but it only seems to work with <code>splot</code>.</p>

<p>Here is a Gnuplot file to see the problem (2 Buildings and 4 roofs) :</p>

<pre><code>set style line 1 linecolor rgbcolor "#777777" linewidth 1
set style increment user
set palette file "-"
0.00000 0.23137 0.22353 0.64314
0.17990 0.47843 0.34510 0.71765
0.32010 0.34902 0.17647 0.55686
0.43990 0.40784 0.10980 0.36471
0.59010 0.46275 0.09020 0.16863
0.78000 0.86667 0.41569 0.24314
0.92990 0.92549 0.66667 0.33725
1.00000 0.97647 0.91765 0.82745
e
set cbrange [50:150]
set cbtics 25
set format cb "%.0f W/m²"
unset xtics
unset ytics
unset ztics
unset border
set colorbox

kzoom=1.0
phi=30.0
theta=60.0
set xyplane 0       # removes the offset of the xy plane
set view equal xyz  # force equal units to all three axes
set view theta,phi,kzoom

set object 1 polygon from \
2.0,0.0,3.0 to \
3.0,0.0,3.5 to \
3.0,2.0,3.5 to \
2.0,2.0,3.0 to \
2.0,0.0,3.0
set object 1 fill solid 0.9 border lw 2 fc palette cb 128.1315 front

set object 2 polygon from \
4.0,0.0,3.0 to \
4.0,2.0,3.0 to \
3.0,2.0,3.5 to \
3.0,0.0,3.5 to \
4.0,0.0,3.0
set object 2 fill solid 0.9 border lw 2 fc palette cb 128.62192 front

set object 3 polygon from \
2.0,0.0,0.0 to \
4.0,0.0,0.0 to \
4.0,0.0,3.0 to \
3.0,0.0,3.5 to \
2.0,0.0,3.0 to \
2.0,0.0,0.0
set object 3 fill solid 0.9 border lw 2 fc palette cb 100.545204

set object 4 polygon from \
4.0,0.0,0.0 to \
4.0,2.0,0.0 to \
4.0,2.0,3.0 to \
4.0,0.0,3.0 to \
4.0,0.0,0.0
set object 4 fill solid 0.9 border lw 2 fc palette cb 85.58082

set object 5 polygon from \
4.0,2.0,0.0 to \
2.0,2.0,0.0 to \
2.0,2.0,3.0 to \
3.0,2.0,3.5 to \
4.0,2.0,3.0 to \
4.0,2.0,0.0
set object 5 fill solid 0.9 border lw 2 fc palette cb 55.88219

set object 6 polygon from \
2.0,2.0,0.0 to \
2.0,0.0,0.0 to \
2.0,0.0,3.0 to \
2.0,2.0,0.0
set object 6 fill solid 0.9 border lw 2 fc palette cb 85.25754

set object 7 polygon from \
2.0,2.0,0.0 to \
2.0,0.0,3.0 to \
2.0,2.0,3.0 to \
2.0,2.0,0.0
set object 7 fill solid 0.9 border lw 2 fc palette cb 85.25754

set object 8 polygon from \
0.0,0.0,3.0 to \
1.0,0.0,3.5 to \
1.0,2.0,3.5 to \
0.0,2.0,3.0 to \
0.0,0.0,3.0
set object 8 fill solid 0.9 border lw 2 fc palette cb 128.1315 front

set object 9 polygon from \
2.0,0.0,3.0 to \
2.0,2.0,3.0 to \
1.0,2.0,3.5 to \
1.0,0.0,3.5 to \
2.0,0.0,3.0
set object 9 fill solid 0.9 border lw 2 fc palette cb 128.62192 front

set object 10 polygon from \
0.0,0.0,0.0 to \
2.0,0.0,0.0 to \
2.0,0.0,3.0 to \
1.0,0.0,3.5 to \
0.0,0.0,3.0 to \
0.0,0.0,0.0
set object 10 fill solid 0.9 border lw 2 fc palette cb 100.545204

set object 11 polygon from \
2.0,0.0,0.0 to \
2.0,2.0,0.0 to \
2.0,2.0,3.0 to \
2.0,0.0,3.0 to \
2.0,0.0,0.0
set object 11 fill solid 0.9 border lw 2 fc palette cb 85.58082

set object 12 polygon from \
2.0,2.0,0.0 to \
0.0,2.0,0.0 to \
0.0,2.0,3.0 to \
1.0,2.0,3.5 to \
2.0,2.0,3.0 to \
2.0,2.0,0.0
set object 12 fill solid 0.9 border lw 2 fc palette cb 55.88219

set object 13 polygon from \
0.0,2.0,0.0 to \
0.0,0.0,0.0 to \
0.0,0.0,3.0 to \
0.0,2.0,0.0
set object 13 fill solid 0.9 border lw 2 fc palette cb 85.25754

set object 14 polygon from \
0.0,2.0,0.0 to \
0.0,0.0,3.0 to \
0.0,2.0,3.0 to \
0.0,2.0,0.0
set object 14 fill solid 0.9 border lw 2 fc palette cb 85.25754

splot "-" with lines notitle ls 1, NaN notitle palette
2.0 0.0 0.0
2.0 2.0 0.0
4.0 2.0 0.0
4.0 0.0 0.0
2.0 0.0 0.0

0.0 0.0 0.0
0.0 2.0 0.0
2.0 2.0 0.0
2.0 0.0 0.0
0.0 0.0 0.0
e

pause mouse
</code></pre>

<p>Thanks for the interest!</p>