Texel density solutions

When using the Mesh converter to capture bark maps from trunk scans, the resulting maps often appear too dense when mapped to branches. This problem is amplified each time a new layer of branches is added as they become successively smaller in diameter.

The following image shows a trunk mapped with the bark generated by the Mesh converter. The same map is then applied, tiling once in U, to each of the next two branch layers. In Texel density render mode, the trunk is green but both branch levels are red, indicating a high texel density.

A trunk and branches in the Tree Window view and in the texel density render mode.

Fixing the texel density

Fixing this problem typically requires further image work on the branch maps or capturing a new branch map from something with a smaller radius (ideally a branch off of the same tree).

However, if you don't expect the camera or player to closely inspect the branches, there is a shortcut to evening out the texel density. In the U section of the UV Mapping group on any Branch generator, enable both Fractional:Enable and Fractional:Auto. Doing so causes the branch to use only as much of the U space of the map needed to exactly match the texel density of its parent (where it attaches).

The UV Mapping group of a Branch generator.

The following image shows the same model with automatic fractional u coordinates on the two branch levels:

A trunk and branches in the Tree Window view and in the Texel density render mode.

Notice that the bark pattern remains consistent across the model and that the texture density is much more even. This method often results in better renderings without any extra maps and is especially good for mid-range VFX shots.

Note

Using this technique means that the map no longer tiles perfectly and there will be a texture seam running along the branch. Only use this option if you know you won't be close enough to detect it.

Best practices

The following list contains a few tips for using automatic fractional u mapping.

  • Use it to preview the model before making detailed, less dense branch maps.

  • The seam location is consistent. Use spine alignment and roll to help hide the seams.

  • Make sure the seams are on the top part of the branches for games where the player might only see the branches from below.

  • Noisier bark patterns make the seam harder to notice.

  • Capture new bark maps when close inspection is unavoidable.