GIMP Version: 2.10.14
Operating System: Linux
GIMP Experience: Intermediate Level

List any relevant plug-ins or scripts:
Fill with Brush to Density (ofnuts)
Random Density Map (RobA)

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I ran this experiment to check behaviors of three approaches to "filling a heightmap using a grayscale brush in lighten-only mode."

I have, off and on for some long years, tried to use GIMP brushes to create 3D models.

My recent idea was to test if the two automated fill methods of which I was aware could use a grayscale brush operating in lighten-only mode to reproduce satisfactory results obtained from painting manually.

In the following, I am using a brush I created by filling a circle with a spherical gradient and then created a new Dynamics w/mapping matrix to vary the size randomly (and between extrema set by editing the default curve for the Size property). Coincidentally the "density map" for RobA's Random Density Map filter is a sph. gradient filled region.

I have been unable to get ofnuts' Fill-Brush-with-Density filter to accomplish my goal; setting brush mode to lighten-only produces an invisible result, whereas using it in normal mode doesn't produce the desired lighten-only effect. [If it can be, please issue a correction.] (First attempts were frustrated by attempting to paint atop a transparent layer with "lighten-only" brushes... Um, yeah, there wood need to be something to lighten.)

Here's what I mean (GIMP project file attached). Maybe you'll find it useful. I know my doppelganger would.

Maybe I don't understand your question? Why not make a 3-D brush and lower the spacing?

Racer,

My ultimate goal is Real 3D as against something that "looks" 3D. I actually "carve" the heightmaps into wood: like pegleg44.

So I'm trying to make something that, when carved, will look like a forest of trees from above.