adminandClaude Opus 4.8
43791abc79
FurShell now reads an RGBA fur map (RGB = per-texel strand colour, A = fur length) so the standalone look can be driven per-texel. Alpha 0 clips the whole shell stack (root included) so a painted body shows through; _SolidRoot keeps the opaque base shell only for the full-coverage prototype. White map default keeps the standalone prototype unchanged. FurShellRenderer drops the MeshFilter requirement and resolves its mesh per frame: on a SkinnedMeshRenderer it borrows the SkinnedColliderBaker's per-frame baked pose so the fur follows the animation with no extra bake. Curvature/gravity now bends strands toward WORLD down (converted into object space via unity_WorldToObject) instead of object-local down, so a rotated player mesh droops downward correctly. Identity rotation is unchanged, so the test sphere is unaffected. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
306 lines
15 KiB
GLSL
306 lines
15 KiB
GLSL
// Generic shell-texturing fur/hair/grass shader (URP). STANDALONE prototype - NOT wired into the
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// MeshPainter paint pipeline yet. The illusion of strands comes from rendering the mesh many times
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// ("shells"), each extruded a little further along its normals, and alpha-clipping a per-cell strand
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// mask that thins toward the tip. It is generic because it needs nothing but positions + normals + a
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// UV set - it works on any mesh.
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//
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// DISPATCH: the shells are drawn by FurShellRenderer.cs via Graphics.RenderMeshInstanced. Each
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// instance is one shell layer; the layer index arrives as SV_InstanceID and drives the extrusion
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// height. Put this material on FurShellRenderer, NOT on a plain MeshRenderer (a MeshRenderer draws a
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// single instance => only the root shell would show). The renderer is the single source of truth: it
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// pushes EVERY tunable parameter below via a MaterialPropertyBlock, so the values authored on the
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// material are only template defaults (they get overridden live at render time).
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//
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// hair vs fur vs grass = the same technique, only parameters differ (length, density, taper, bend).
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Shader "Custom/FurShell"
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{
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Properties
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{
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[Header(Fur Shape)]
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_ShellCount("Shell Count (driven by FurShellRenderer)", Range(1, 64)) = 32
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_ShellLength("Fur Length", Range(0.0, 2.0)) = 0.15
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_Density("Strand Density", Range(1.0, 1000.0)) = 250
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_Thickness("Strand Thickness", Range(0.0, 1.0)) = 0.5
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_Taper("Tip Taper", Range(0.1, 8.0)) = 2.0
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_TipFill("Tip Fill (bridge shell gaps)", Range(0.0, 1.0)) = 0.35
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_Curvature("Gravity / Curl Bend", Range(0.0, 1.0)) = 0.25
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_DirRandomness("Direction Randomness (per strand)", Range(0.0, 1.0)) = 0.3
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_SilhouetteStretch("Silhouette Strand Stretch", Range(0.0, 5.0)) = 2.0
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[Header(Fur Shading)]
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[MainTexture] _BaseMap("Albedo", 2D) = "white" {}
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[MainColor] _BaseColor("Root Tint", Color) = (0.42, 0.32, 0.20, 1)
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_TipColor("Tip Tint", Color) = (0.62, 0.52, 0.36, 1)
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_RootAO("Root Darkening (fake AO)", Range(0.0, 1.0)) = 0.45
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_RimPower("Rim / Backlight Power", Range(0.5, 8.0)) = 3.0
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_RimStrength("Rim / Backlight Strength", Range(0.0, 2.0)) = 0.4
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[Header(Fur Map)]
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// RGB = per-texel strand colour, A = fur length (0 = bald here, 1 = full length). White default
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// means "full-length fur everywhere" so the standalone prototype behaves as before with no map.
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_FurMap("Fur Map (RGB color, A length)", 2D) = "white" {}
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_FurThreshold("Fur Cutoff (alpha)", Range(0.0, 1.0)) = 0.0
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// Opaque base shell. On = solid root (full-coverage prototype); Off = the root also clips to the
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// map so the painted body shows between strands (avatar integration).
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[ToggleUI] _SolidRoot("Solid Root", Float) = 1
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[Header(Wind)]
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_WindStrength("Wind Strength", Range(0.0, 1.0)) = 0.1
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_WindSpeed("Wind Speed", Range(0.0, 10.0)) = 2.0
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_WindFrequency("Wind Spatial Frequency", Range(0.0, 10.0)) = 1.0
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_WindDirection("Wind Direction (object XZ)", Vector) = (1, 0, 0, 0)
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}
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SubShader
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{
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Tags
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{
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"RenderType" = "Opaque"
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"RenderPipeline" = "UniversalPipeline"
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"Queue" = "Geometry"
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}
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LOD 200
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Pass
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{
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Name "FurForward"
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Tags { "LightMode" = "UniversalForward" }
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Cull Back
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ZWrite On
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ZTest LEqual
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HLSLPROGRAM
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#pragma target 3.5
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#pragma vertex vert
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#pragma fragment frag
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#pragma multi_compile_instancing
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#pragma multi_compile _ _MAIN_LIGHT_SHADOWS _MAIN_LIGHT_SHADOWS_CASCADE _MAIN_LIGHT_SHADOWS_SCREEN
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#pragma multi_compile_fragment _ _SHADOWS_SOFT
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#pragma multi_compile _ _ADDITIONAL_LIGHTS_VERTEX _ADDITIONAL_LIGHTS
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#pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS
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#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
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#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
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CBUFFER_START(UnityPerMaterial)
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float4 _BaseMap_ST;
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half4 _BaseColor;
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half4 _TipColor;
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float _ShellCount;
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float _ShellLength;
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float _Density;
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float _Thickness;
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float _Taper;
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float _TipFill;
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float _Curvature;
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float _DirRandomness;
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float _SilhouetteStretch;
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half _RootAO;
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half _RimPower;
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half _RimStrength;
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float _FurThreshold;
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float _SolidRoot;
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float _WindStrength;
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float _WindSpeed;
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float _WindFrequency;
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float4 _WindDirection;
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CBUFFER_END
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TEXTURE2D(_BaseMap);
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SAMPLER(sampler_BaseMap);
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TEXTURE2D(_FurMap);
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SAMPLER(sampler_FurMap);
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struct Attributes
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{
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float4 positionOS : POSITION;
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float3 normalOS : NORMAL;
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float2 uv : TEXCOORD0;
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UNITY_VERTEX_INPUT_INSTANCE_ID
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};
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struct Varyings
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{
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float4 positionCS : SV_POSITION;
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float2 uv : TEXCOORD0;
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float3 normalWS : TEXCOORD1;
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float3 positionWS : TEXCOORD2;
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float shellH : TEXCOORD3; // 0 = root, 1 = tip
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};
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// cheap deterministic 2D hash -> [0,1)
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float Hash21(float2 p)
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{
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p = frac(p * float2(123.34, 345.45));
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p += dot(p, p + 34.345);
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return frac(p.x * p.y);
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}
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Varyings vert(Attributes input)
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{
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Varyings output = (Varyings)0;
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UNITY_SETUP_INSTANCE_ID(input);
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// shell layer index -> normalized height (guarded so the non-instanced variant compiles)
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#if UNITY_ANY_INSTANCING_ENABLED
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uint shellIndex = input.instanceID;
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#else
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uint shellIndex = 0u;
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#endif
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float count = max(_ShellCount, 1.0);
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float h = (count <= 1.0) ? 0.0 : (float)shellIndex / (count - 1.0);
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// extrude along the normal; bend the tips down with h^2 for a gravity/curl droop
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float3 posOS = input.positionOS.xyz + input.normalOS * (_ShellLength * h);
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// gravity pulls toward WORLD down, so strands hang downward no matter how the mesh is
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// oriented - a rotated player mesh would otherwise droop along its own local down. Convert
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// world down into object space (the extrusion space) so the droop magnitude stays consistent
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// with _ShellLength under the object-to-world transform.
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float3 downOS = normalize(mul((float3x3)unity_WorldToObject, float3(0.0, -1.0, 0.0)));
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posOS += downOS * (_Curvature * _ShellLength * h * h);
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// wind sway: nudge each shell along the wind direction (object XZ) by a time-varying
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// amount. The phase is offset by object-space position so a gust rolls across the surface,
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// and the h^2 weight keeps roots planted while tips travel most => the stacked shells read
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// as strands bending in the wind.
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float2 wdir = _WindDirection.xy;
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float wlen = length(wdir);
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wdir = (wlen > 1e-4) ? (wdir / wlen) : float2(1.0, 0.0);
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float phase = _Time.y * _WindSpeed + (input.positionOS.x + input.positionOS.z) * _WindFrequency;
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posOS.xz += wdir * (_WindStrength * _ShellLength * h * h * sin(phase));
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VertexPositionInputs vp = GetVertexPositionInputs(posOS);
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VertexNormalInputs vn = GetVertexNormalInputs(input.normalOS);
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output.positionCS = vp.positionCS;
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output.positionWS = vp.positionWS;
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output.normalWS = vn.normalWS;
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output.uv = TRANSFORM_TEX(input.uv, _BaseMap);
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output.shellH = h;
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return output;
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}
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half4 frag(Varyings input) : SV_Target
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{
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float h = input.shellH;
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float3 N = normalize(input.normalWS);
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float3 V = GetWorldSpaceNormalizeViewDir(input.positionWS);
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// fur map: RGB = strand colour, A = fur length. White default (no map) => full-length fur
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// everywhere, so the standalone prototype is unchanged.
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half4 furSample = SAMPLE_TEXTURE2D(_FurMap, sampler_FurMap, input.uv);
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float furLen = furSample.a;
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// --- strand mask: one strand per cell, random length, radially tapered toward the tip ---
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float2 g = input.uv * _Density;
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float2 cell = floor(g);
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float strandLen = Hash21(cell); // this strand's random max height (0..1)
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// per-strand lean: shift the cell-local strand centre by a random direction that grows
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// with height, so each strand tilts its own way. This is a fragment-space lean - geometry
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// is shared per vertex while strands are per cell, so the tilt has to live here, not in the
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// extrusion.
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float rndAngle = Hash21(cell + 3.7) * 6.2831853;
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float2 leanDir = float2(cos(rndAngle), sin(rndAngle));
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float2 local = (frac(g) * 2.0 - 1.0) - leanDir * (_DirRandomness * h);
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// silhouette stretch: at grazing angles the flat shell slices are viewed edge-on, so a
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// strand breaks into squished, separated dots. Elongate the strand footprint along the
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// tangent-space view direction - the axis the extruded shells drift apart on screen - so
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// consecutive slices overlap into a continuous strand near the rim. The tangent frame is
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// rebuilt from screen-space derivatives (Schueler's cotangent trick), so this stays generic:
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// no per-mesh tangents required. graze^2 confines the effect to the silhouette, leaving the
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// head-on look untouched. The branch is on a uniform, so the derivatives stay quad-uniform
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// (safe) and the cost is skipped when the feature is off; at stretch==1 the basis rotation is
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// a pure rotation => identity, so ramping it in is continuous.
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if (_SilhouetteStretch > 0.0)
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{
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float graze = 1.0 - saturate(dot(N, V));
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graze *= graze;
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float3 dp1 = ddx(input.positionWS);
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float3 dp2 = ddy(input.positionWS);
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float2 duv1 = ddx(input.uv);
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float2 duv2 = ddy(input.uv);
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float3 dp2perp = cross(dp2, N);
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float3 dp1perp = cross(N, dp1);
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float3 T = dp2perp * duv1.x + dp1perp * duv2.x;
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float3 B = dp2perp * duv1.y + dp1perp * duv2.y;
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float invmax = rsqrt(max(dot(T, T), dot(B, B)));
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T *= invmax; B *= invmax;
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float2 vt = float2(dot(V, T), dot(V, B));
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float vlen = length(vt);
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float2 sdir = (vlen > 1e-4) ? (vt / vlen) : float2(1.0, 0.0);
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float stretch = 1.0 + _SilhouetteStretch * graze;
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float along = dot(local, sdir) / stretch; // compress coord => elongate footprint along sdir
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float perp = dot(local, float2(-sdir.y, sdir.x));
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local = float2(along, perp);
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}
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float dist = length(local);
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// allowed radius shrinks with height => the strand narrows toward its tip. _TipFill is a
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// floor on that radius (as a fraction of the base thickness): the taper only thins a strand
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// down to _TipFill, never to a point. With few shells the pointy tip breaks into floating
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// discs ("dots") because consecutive shell slices stop overlapping; holding a minimum radius
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// keeps neighbouring slices wide enough to bridge the inter-shell gap. 0 = sharp needles
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// (dots return), higher = fuller, slightly rounded tips.
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float taperedR = pow(saturate(1.0 - h), _Taper * 0.5);
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float radius = _Thickness * max(taperedR, _TipFill);
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// The fur map's alpha caps this strand's height: 0 => bald, so the whole shell stack
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// (root included) clips and the body shows through; 1 => the strand reaches its full
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// random length. _SolidRoot keeps the base shell opaque for the full-coverage prototype;
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// on the painted avatar it is turned OFF so the camo body stays visible between strands
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// instead of being sealed under a solid root (which would also Z-fight the body).
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float effectiveLen = strandLen * furLen;
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half alpha;
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if (furLen <= _FurThreshold)
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alpha = 0.0h;
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else if (h <= 0.0 && _SolidRoot > 0.5)
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alpha = 1.0h;
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else
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alpha = (dist < radius && h <= effectiveLen) ? 1.0h : 0.0h;
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clip(alpha - 0.5h);
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// --- shading (lightweight URP) ---
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half3 albedo = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, input.uv).rgb * furSample.rgb * _BaseColor.rgb;
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albedo = lerp(albedo, _TipColor.rgb, h);
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half ao = lerp(1.0h - _RootAO, 1.0h, h); // roots darker (fake self-occlusion)
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albedo *= ao;
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float4 shadowCoord = TransformWorldToShadowCoord(input.positionWS);
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Light mainLight = GetMainLight(shadowCoord);
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half ndotl = saturate(dot(N, mainLight.direction)) * 0.5h + 0.5h; // soft half-lambert
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half3 lighting = mainLight.color * (ndotl * mainLight.shadowAttenuation);
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half3 ambient = SampleSH(N);
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half3 color = albedo * (lighting + ambient);
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#ifdef _ADDITIONAL_LIGHTS
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uint addCount = GetAdditionalLightsCount();
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for (uint i = 0u; i < addCount; i++)
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{
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Light lt = GetAdditionalLight(i, input.positionWS);
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half nl = saturate(dot(N, lt.direction)) * 0.5h + 0.5h;
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color += albedo * lt.color * (nl * lt.distanceAttenuation * lt.shadowAttenuation);
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}
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#endif
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// rim / backlight scatter: brighter fuzz at grazing angles, strongest at the tips
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half rim = pow(saturate(1.0h - saturate(dot(N, V))), _RimPower) * _RimStrength * h;
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color += rim * mainLight.color * albedo;
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return half4(color, 1.0h);
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}
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ENDHLSL
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}
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}
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FallBack Off
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}
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