With M9, I have a project with

a) a drawing with building areas called 'B'

b) a DSM .LAZ file called 'L', with a height attribute Z (height, in metres)

both files have the same date & projection

c) I clipped 'L', keeping the points that are contained within 'B'

d) I subsequently ran a Voronoi transform on 'L', and called the resulting drawing 'VL'

e) then I ran a Overlay Identity Transform with the 'VL' drawing as source , 'B' as overlay and called the resulting drawing VLinB

f) I deleted the voronoi areas in 'VLinB' that are not contained within 'B'

g) I updated VLinB with the Z (height attribute) from 'B'

I would like to calculate the slope and the aspect for each area in 'VLinB'.

I found in the manual the slope and aspect transforms starting with a elevation raster .

https://manifold.net/doc/mfd9/transform_-_tiles__slope.htm

What steps need I undertake to calculate slope and aspect for each area starting from this 'VinB' drawing ?

What are the possible solutions within M9?

OK.

In the meantime I found this information in the manual which helped a lot !

convert vector to raster

https://manifold.net/doc/mfd9/spatial_join_example___convert_vector_to_raster.htm

If I understand correctly, it sounds like you are already on the right track, but I would suggest grabbing the points contained within B and of the correct classification (if this is appropriate or if you have a classification field 2 is normally ground I believe).

Next, interpolate a surface presumably DEM from the point set using something quick such as tinning (https://manifold.net/doc/mfd9/transform_-_geometry__interpolate.htm) and then derive slope and aspect from this surface.

All of this can be done in the GUI using the transforms and even better, you can harvest the SQL and build a semi or automated process using them as required.

Landsystems Ltd ... Know your land | www.landsystems.co.nz

@danb : Thank you.

I will dive into 'interpolation' and have a closer look.