[Qgis-user] Layer Ordering for KMZ

Sun Aug 15 12:30:42 PDT 2021

>From the docs I had the impression that the draw order was used for
linestrings and wasn't sure it would work on points. I initially attempted
to apply the tag to an entire "folder" element but it seems to only work on
individual geometries. I was also somewhat pleasantly surprised to find
that it does work on point features, although manually applying that to
each feature would be a bit of a pain.

I made a modified version of my previous bulk qgis vectors to kmz script to
include drawordering and it seems to work fine (on basic geometry
types), although points seem to still always render on top of lines and
polygons, which I suppose may be the expected behaviour.

Not quite a production grade utility, but probably a lot easier than
manually running a find and replace macro on kmls:
https://github.com/zacharlie/effective-dollop/blob/main/pyqgis/qgis-vectors-to-kmz-with-draw-ordering.py

Hopefully that's useful to someone. I'd be interested to learn more about
the draw order behaviour versus elevation (in terms of priority etc) and
the limitations between geometry types.

Regards

On Sun, 15 Aug 2021 at 17:12, Jeff Sonnentag <jsonnentag at llenviroinc.com>
wrote:

> I have read other people’s solutions to the problem in the past and they
> recommended setting the clamp elevation to various levels above the surface
> in order to try forcing apparent render order.  It seemed to mostly work.
> But I will definitely have to try the <gx:drawOrder> mentioned in another
> response too.  You just probably can’t do that from within Google Earth and
> have to hunt through a lot of KML the locations to insert things.
>
>
>
>
>
> *From:* Qgis-user <qgis-user-bounces at lists.osgeo.org> * On Behalf Of *Charles
> Dixon-Paver
> *Sent:* Sunday, August 15, 2021 6:54 AM
> *To:* krishna Ayyala <ayyalakrishna at gmail.com>
> *Cc:* qgis-user <qgis-user at lists.osgeo.org>; Andrea Giudiceandrea <
> andreaerdna at libero.it>
> *Subject:* Re: [Qgis-user] Layer Ordering for KMZ
>
>
>
> I just had a chance to look at the samples and it seems my hypothesis was
> in fact correct.
>
>
>
> I had expected that because Google Earth functions in 3D that it may
> perhaps render placemarkl symbols based on the orientation of the "camera"
> to the point, but from my assessment it definitely seems that altitude is
> the deciding factor when it comes to determining the rendering order of
> symbols.
>
>
>
> By exporting the big points with "clamptoground" active, but using the
> relative to ground and altitude addend functionality in the KML tools
> export (see screenshot.png), the small points are "higher" in altitude and
> render on top of the big points regardless of orientation. In the example I
> provided (desired_output.kmz) I "lifted" the small points 25m off the
> ground.
>
>
>
> By using the $x and $y attributes on the supplied shp data in QGIS, it
> became apparent that there were some offsets between the point positions:
>
>
>
> Small Points
>
> Big Points
>
> wkt_geom
>
> id
>
> Name
>
> x
>
> y
>
> wkt_geom
>
> id
>
> Name
>
> x
>
> y
>
> Point (-98.94705168629492675 29.6341226203915511)
>
> 1
>
> A
>
> -98.94705168629493
>
> 29.63412262039155
>
> Point (-98.94705168490899894 29.63412262285223875)
>
> 1
>
> E
>
> -98.947051684909
>
> 29.63412262285224
>
> Point (-98.93203732506144377 29.63666293420626374)
>
> 2
>
> B
>
> -98.93203732506144
>
> 29.636662934206264
>
> Point (-98.9320373399207682 29.63666292869620733)
>
> 2
>
> F
>
> -98.93203733992077
>
> 29.636662928696207
>
> Point (-98.94352477360057208 29.62202767741294451)
>
> 3
>
> C
>
> -98.94352477360057
>
> 29.622027677412945
>
> Point (-98.94352558873751491 29.62202773383394927)
>
> 3
>
> G
>
> -98.94352558873751
>
> 29.62202773383395
>
> Point (-98.92999000422139488 29.62559164108440513)
>
> 4
>
> D
>
> -98.9299900042214
>
> 29.625591641084405
>
> Point (-98.92998992924056267 29.62559174501802062)
>
> 4
>
> H
>
> -98.92998992924056
>
> 29.62559174501802
>
>
>
>
>
> I expect the reason "some" points rendered on top and not others, is that
> the slight positional offset would have likely ended up giving the points
> different altitudes based on the "clamp to ground" positions.
>
>
>
> There are a number of approaches you can utilise to resolve this issue,
> depending on your needs. One is to export the KMZ with a multilayer symbol
> from QGIS (the style will become a single png), if you intend on using the
> same geometries. This would yield a more consistent result, however it of
> course would not work on different layers.
>
>
>
> I have attached a zip file (kmz_data.zip) with the following elements for
> your review:
>
>    - screenshot.png - KML Tools export settings for increasing point
>    position from ground
>    - desired_output.kmz - The desired output as expressed by OP
>    - points_big_clamped_to_ground.kmz - Big points layer exported with
>    clamp to ground and used in desired output
>    - points_single_symbol_one.kmz - A multilayer QGIS symbol used in a KMZ
>    - points_single_symbol_one.qml - A QML style for anyone unfamiliar
>    with multisymbol styles
>    - points_single_symbol_two.kmz - A multilayer QGIS symbol with offset
>    applied to get a style closer to original kmz
>    - points_small_with_altitude.kmz  - Small points layer exported with
>    relative to ground and addended altitude, used in desired output
>    - points_with_shift.kmz - Point positions shifted west to display how
>    altitude seems to impact rendering in google earth more than orientation
>
> The export tools also provide various data driven options which may be
> used instead of the addend altitude feature.
>
>
>
> Hope that clears this up for everyone. I'd be interested to know if this
> resolves the issues that were being experienced.
>
>
>
> Regards
>
>
>
>
>
> On Sun, 15 Aug 2021 at 05:04, David Strip <qgis-user at stripfamily.net>
> wrote:
>
> I tried your file on   Google Earth Pro 7.3.4.8248 (64-bit) on Win10. I
> get an even stranger result - two of the small circles appear on top of the
> big circles, the other two behind.
> Both layers are listed as clamp to ground.
>
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