Atlas Workflow

The atlas pipeline brings the 2D imagery of foliage atlases (the kind you get out of a delighting workflow, or from a photographic shoot of leaves on a backdrop) into Natsura, and turns it into ingredients for the meshing system. The output is geometry plus material data that the decorations can consume, most directly the Cluster Decoration for flat-card foliage, but also the Assembly Decoration where the source library is built from atlas cards rather than from modelled assemblies.

The atlas pipeline is one of the workflows behind the Leaves, Foliage & Canopies concept, and it produces the leaf side of Materials. For the broader decoration system the atlases feed into, see Decorations; for the foliage placement workflows that consume atlas output, see Assemblies.

What an atlas is

An atlas is a single image (or a set of channels: colour, alpha, roughness, height, normal, subsurface) that packs multiple leaf or foliage cards into one texture. The image is two-dimensional; the pipeline below turns it into something that can be cut out, traced, embossed, and meshed into geometry that takes the place of individually-modelled leaves at render time.

The pipeline works on whatever atlas source you have: a delighted scan, a hand-painted texture, a photographic capture against a backdrop, a synthetic atlas generated elsewhere.

When to use the atlas pipeline

The atlas pipeline is the right tool when:

• The source for your foliage is a 2D image rather than modelled or scanned 3D geometry.
• The output target is flat-card or low-poly foliage where the silhouette comes from a traced outline rather than from modelled mesh.
• A delighting / photogrammetry workflow has produced atlas-style textures that need to flow into a Natsura library.

For modelled foliage (rigged branches, sculpted clusters) the Assembly workflow is the better entry point. For trunk and bark texture extraction from scanned highpoly geometry, see Scans.

Two routes through the pipeline

Like other Natsura workflows, the atlas pipeline supports both a high-level guided route and a granular step-by-step route.

High-level route: Atlas Wizard. A single wizard node packages the import flow and gets you to a usable atlas in a few clicks. Recommended starting point when an atlas is new and you want to see it round-trip through Natsura before diving into individual settings.

Granular route: the individual Atlas nodes. Drop into the constituent nodes when you need control the wizard doesn't give: per-channel material derivation, a specific layout, a particular trace method, a different emboss treatment.

The pipeline

The atlas pipeline has six or seven steps depending on whether the output is flat-card or 3D-embossed. Each step has its own node; the wizard composes a typical sequence.

1. Import

Bring the atlas image (or set of channel images: colour, alpha, roughness, height, normal, subsurface) into the workflow. Handled by Atlas Import, or as part of Atlas Wizard.

2. Lay out

Identify the individual cards in the atlas image and lay them out for further processing. Handled by Atlas Layout.

3. Material

Derive the material channels for each card from the source atlas (colour, alpha, roughness, height, normal, subsurface), with a per-channel "Derive" pipeline that sources, processes, and writes each channel separately. The alpha channel supports chromakey and connectivity-based extraction; height drives the optional emboss step downstream. See Atlas Material.

4. 3D (optional)

Lift the flat cards into 3D where geometric thickness is wanted (for example, to produce embossed leaves rather than purely flat ones). Handled by Atlas 3D.

5. Emboss (optional)

Use the height channel to drive surface displacement on the lifted cards. Handled by Atlas Emboss.

6. Trace

Convert the atlas alpha (or the lifted/embossed card) into a traced polygonal outline mesh whose silhouette follows the alpha rather than sitting on a rectangular quad. See Atlas Trace. The trace step is what makes atlas-sourced cards read cleanly as leaves rather than as rectangular planes with masked alpha.

7. Remesh

Clean up the traced mesh into a uniform polygonal output ready for use in a foliage library. Handled by Atlas Remesh.

What the output is used for

Once an atlas has been through the pipeline, the resulting cards (or 3D-embossed leaves) become input geometry for the foliage decorations. The two consumers:

• The Cluster Decoration takes the atlas cards as the deformable input mesh and bends them along the skeleton.
• The Assembly Decoration takes a library of atlas-derived cards (after grouping them into rigged assemblies via the Assembly Resource) and places them at spawn points on the tree.

State of the pipeline

Less time has been spent on the atlas pipeline than on the core meshing pipelines, and that shows in the documentation. The pipeline works end-to-end and is used in production for atlas-derived foliage libraries, but per-node documentation is still being written and individual nodes may shift before this pipeline reaches the same maturity as the trunk and assembly workflows. Treat the warnings and TODOs as honest signals about where to expect changes.

Related

For the decorations that consume atlas output, see Cluster Decoration and Assembly Decoration. For the per-node documentation that exists today, see Atlas Material and Atlas Trace; the remaining Atlas nodes have placeholder pages and will be filled out as recorded references and reviewed reference work land.

Visual pending.