The swirling strokes in this were achieved with the liquid ink pine preset in Corel Painter 2016. Tap or click image for ~2K resolution, free for personal use. Here's a link to prints and merchandise available at pixels.com, and another link to prints available at ImageKind at up to ~ 35" x 56".

The following variant and resource images which I made along the way, I release into the Public Domain:

Variant via the Filter Forge "side to side" filter by Skybase:

An alpha resource via the Filter Forge Terrain Hightfield Generator by LigH; I used this (and variants of it) as a transparency channel in filter layers to make uneven interesting application of filters: