Material Setup

QuickSDFTool outputs a threshold texture intended to drive stylized light-to-shadow transitions. The exact shader graph can vary by project, but the core idea is stable: compare a light-angle value against the generated texture value, then use the result to choose lit or shadow color.

Basic Shader Concept

light direction / artist control value
    compared with
SDF threshold map sample
    produces
toon shadow mask

Use the included Content/Materials/M_SDFToon.uasset as the first reference material. It is meant to show the expected data flow rather than dictate a final production shader.

Texture Expectations

• Generated maps are saved under /Game/QuickSDF_GENERATED/ by default.
• The output is designed for precision, so keep compression and color-space settings appropriate for data textures.
• Treat the map as threshold data, not as a color/albedo texture.
• If the shadow appears inverted, verify the material comparison direction and the light-angle value first. The built-in Generated SDF preview uses the same exported threshold-map layout as the saved texture.

Original Shading Bake Parameters

M_OriginalShading receives these dynamic parameters during the original-shading bake:

• Angle: authored light angle in degrees.
• BakeForwardAngleOffset: forward-axis offset in degrees. Static Mesh uses 0; Skeletal Mesh uses 90 because the visual forward axis is treated as component local +Y.

For actor-rotation-independent output, build the bake direction from Angle + BakeForwardAngleOffset and compare it with normalized PixelNormalWS.rg in the material baking space. QuickSDF neutralizes the primitive transform for this bake, so do not transform PixelNormalWS from world to local in M_OriginalShading.

Mesh Preview Material Parameters

QuickSDF loads two mesh preview material interfaces:

• Opaque replacement: /QuickSDFTool/Materials/M_PreviewMat.M_PreviewMat
• SceneColor multiply overlay: /QuickSDFTool/Materials/M_PreviewSceneColorOverlay.M_PreviewSceneColorOverlay

The opaque material is used for replacement preview and for the upper-left 2D texture preview. The overlay material is used only for the original-material overlay preview. Blend mode is not changed dynamically from C++; M_PreviewSceneColorOverlay must be a real material asset whose Blend Mode is Translucent. Do not make it a material instance of opaque M_PreviewMat, because opaque parents cannot use SceneColor.

Preview modes:

• Original + Painted: restores the original material slots and applies the translucent preview with UMeshComponent::SetOverlayMaterial().
• Painted Texture: applies the opaque preview as a replacement material.
• Painted + UV: applies the opaque preview as a replacement material.
• Painted + Shadow: applies the opaque preview as a replacement material.

The default mesh preview mode is Original + Painted.

Both dynamic material instances receive these parameters:

• Texture BaseColor: active mask render target.
• Scalar PreviewMode: 0 = Painted Texture, 1 = Painted + UV, 2 = Painted + Shadow.
• Scalar UVChannel: active UV channel index.
• Scalar Angle: active timeline angle in degrees. This matches M_OriginalShading.
• Scalar BakeForwardAngleOffset: forward-axis offset in degrees. This matches M_OriginalShading.

For Painted + Shadow, use the same Angle + BakeForwardAngleOffset direction calculation as M_OriginalShading so the mesh preview matches the baked mask. Only M_PreviewSceneColorOverlay should be translucent. M_PreviewMat should stay opaque and should not contain a SceneColor node.

For Original + Painted, implement M_PreviewSceneColorOverlay with SceneColor multiplied by the black/white painted mask from BaseColor. C++ always sends PreviewMode = 0 to this overlay path.

The upper-left 2D texture preview uses a separate dynamic instance of M_PreviewMat and always forces PreviewMode = 0, so it remains a black/white painted texture preview regardless of the selected mesh preview mode.

Monopolar vs Bipolar

• Monopolar is the simpler case. Symmetric output can use the same threshold across RGB; separate 0-90 / 90-180 output uses R/A.
• Bipolar stores shadow enter/exit behavior separately, useful for asymmetric shapes where a shadow enters and leaves a region differently as the light rotates. Values are generated in the legacy R/G/B/A field and exported with an R/A/B/G swizzle, preserving B as the 0-90 exit value.

LilToon / General Toon Shader Notes

QuickSDFTool does not require a specific toon shader. For LilToon-inspired or similar pipelines, use the generated map as an authored control texture:

• Sample the threshold map in the same UV channel used during painting.
• Convert the current light angle or directional term into the same normalized range expected by the material.
• Compare the light value and threshold value.
• Blend lit and shadow ramps with the comparison result.

Keep the first integration simple. Once the direction and value range are confirmed, add project-specific ramps, softening, and color grading.