ZBrush Tip: Generate Clean Diffuse, Specular and SSS Passes with BPR RenderPass

Extract clean Diffuse, Specular, and SSS channels with BPR RenderPass to gain full control in post without re-rendering.

Preparation for clean passes

• Avoid MatCaps when you need separate lighting channels. Use Standard/skin materials so BPR can output true Diffuse and Specular contributions.
• In Render > Render Properties, enable Shadows, AO, and SSS as needed. Use SkinShade4 or another SSS-capable material to generate a meaningful SSS pass.
• Shape highlights with LightCap or standard lights; Specular intensity is material-driven, so set your spec/roughness look here.
• Set Document size to your final resolution; for extra crisp anti-aliasing, render at 2x and downsample later.

Generate the passes

• Press BPR to render. Open Render > RenderPass.
• Export Diffuse, Specular, and SSS. Also grab AO, Shadow, ZDepth, and Mask for robust compositing. Use PSD/PNG for color passes; use 16‑bit PSD/TIFF for ZDepth to avoid banding.
• Name consistently (e.g., proj_v01_diffuse.psd, proj_v01_spec.psd) to keep revisions traceable.

Compositing cheat sheet (Photoshop, After Effects, or Nuke)

• Base: Diffuse (Normal blend, 100%). This is your lit diffuse contribution, not pure albedo.
• Specular: Screen or Linear Dodge (Add), 20–60%. Drive gloss hotspots, mask per material if needed.
• SSS: Screen or Soft Light, 15–50%. Great for skin ear/nose glow; paint a mask to localize.
• AO: Multiply, 30–70%. Tightens creases; avoid over-darkening broad areas.
• Shadows: Multiply, 60–90%. Controls contact strength independently of the base.
• ZDepth: Use for Lens Blur/Depth of Field; invert if your compositor expects white = near.
• Mask: Isolate the model cleanly from background for grading and relighting.

Quality boosters

• Refine BPR Shadows/AO (Rays, Angle, Blur) to reduce noise before export. Higher rays yield smoother results.
• For anti-aliasing, either enable AAHalf or render larger and scale down; this preserves crisp edge transitions between passes.
• Keep BPR Filters off when generating passes; apply look effects in comp to maintain channel purity.
• Work in a linear workflow when possible: keep passes in linear space and apply sRGB only at output.

Albedo vs. Diffuse note

• Need true albedo (unlit color)? Bake Texture From Polypaint or render once with Flat Color material. The BPR Diffuse pass is lighting-aware, which is ideal for relighting blends but not a pure color map.

Pipeline tips

• Batch your exports per lookdev iteration to compare passes A/B in comp.
• Archive the LightCap and materials alongside the passes so rerenders match exactly.

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