tfTrace uses ray tracing (shot from the terrain grid (at 0.0 altitude) upwards, to bring 3D polygon geometry into the TerraformFX heightfield system.

tfTrace User Interface (UI) settings.

Object

Drag and drop (or use the eye-dropper tool to select) the 3D polygon geometry into this field to incorporate it into the TerraformFX terrain.

The scene Platonic geometry (visible in the left-hand image), having been dropped into the Object field and the resulting terrain on the right.

Intersection Normal

Set as Back Only, by default, this defines whether tfTrace should trace or ignore a surface if the ray hits it from the front or the back, depending on the surface normal.

The alternative is Front Only.

The two Intersection Normal options of Back Only (on the left) and Front Only (on the right).

Use Intersection

Set as Top, by default. this uses the multiple intersection points available in polygon geometry.

The other setting is Bottom.