[QGIS-Developer] Point Clouds and Elevation slicing/filtering

[Nyall Dawson]

On Wed, 9 Dec 2020 at 00:10, Andreas Neumann <andreas at qgis.org> wrote:
>
> Hi,
>
> I wonder how I can achieve the elevation slicing / filtering shown here:
>
> https://twitter.com/nyalldawson/status/1331092360818614274?s=20
>
> Is there Python code involved to do that? No GUI yet?

No GUI yet (see below). Try the following Python code:


w=QgsFloatingWidget(iface.mainWindow())
l=QVBoxLayout()
slider = QgsRangeSlider(Qt.Vertical)
slider.setFlippedDirection(True)

range = QgsElevationUtils.calculateZRangeForProject(QgsProject.instance())
slider.setRangeLimits(range.lower() * 100,range.upper()*100)
l.addWidget(slider)
w.setSizePolicy( QSizePolicy.Fixed, QSizePolicy.Preferred)
w.setFixedSize(500,200)
w.setLayout(l)
w.setAnchorWidget(iface.mapCanvas())
w.setAnchorPoint(QgsFloatingWidget.TopLeft)
w.setAnchorWidgetPoint(QgsFloatingWidget.TopLeft)
w.show()
w.raise_()

def range_changed(lower,upper):
    iface.mapCanvas().setZRange(QgsDoubleRange(lower/100,upper/100))

slider.rangeChanged.connect(range_changed)

> That slicing looks incredibly useful to me.

I've been struggling with how to expose this to users, which is why
it's all just python code for now. I'm also starting to think I need
to make the api a bit more generic and potentially allow for slicing
based on any kind of attribute, not just elevation/z based slicing.
There's potentially many different variables which users may want to
interactively slice using and I'm leaning toward reworking the api to
allow for more flexibility, including allowing multiple different
range definition for layers. E.g. you could have a vector point layer
with both a "z" attribute and a "concentration" attribute, and we
could expose sliders for filtering on both the z AND concentration
ranges...

Something to think more about :)

Nyall


>
> I know I could change the min/max values and clip them in the symbology settings, but that isn't very interactive.
>
> Thanks,
> Andreas
> htIs there Python
> --
> Andreas Neumann
> QGIS.ORG board member (treasurer)
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