diff options
| -rw-r--r-- | impostor.cginc | 114 |
1 files changed, 95 insertions, 19 deletions
diff --git a/impostor.cginc b/impostor.cginc index fb41b19..d328223 100644 --- a/impostor.cginc +++ b/impostor.cginc @@ -31,13 +31,13 @@ void BillboardBasis(float3 fwd, out float3 right, out float3 up) { up = cross(fwd, right); } -int2 GetCell(float3 viewDir) { +float2 GridFromDir(float3 viewDir, float gridRes) { float2 uv = HemiOctEncode(viewDir) * 0.5 + 0.5; - return clamp(int2(round(uv * (_GridResolution - 1))), 0, _GridResolution - 1); + return clamp(uv * (gridRes - 1), 0, gridRes - 1); } -float3 CellDir(int2 cell) { - float2 uv = float2(cell) / max(1.0, _GridResolution - 1) * 2.0 - 1.0; +float3 DirFromCell(float2 cell, float gridRes) { + float2 uv = cell / max(1.0, gridRes - 1) * 2.0 - 1.0; return HemiOctDecode(uv); } @@ -45,6 +45,38 @@ float4 SampleAtlas(float2 uv, float2 cell) { return _ImpostorAtlas.Sample(bilinear_clamp_s, (cell + uv) / _GridResolution); } +// Compute blend weights for 3 frames in a grid cell triangle +// .xyz = weights for frames 1,2,3 +// .w = which triangle (0 = lower-left, 1 = upper-right) +float4 QuadBlendWeights(float2 frac) { + float4 res; + res.x = min(1.0 - frac.x, 1.0 - frac.y); + res.y = abs(frac.x - frac.y); + res.z = min(frac.x, frac.y); + res.w = ceil(frac.x - frac.y); + return res; +} + +// Compute UV on a virtual plane facing frameDir +float2 VirtualPlaneUV(float3 frameDir, float3 pivotToCam, float3 vertexToCam, float size) { + float3 planeN = normalize(frameDir); + float3 up = abs(planeN.y) > 0.999 ? float3(0,0,1) : float3(0,1,0); + float3 planeX = normalize(cross(planeN, up)); + float3 planeY = normalize(cross(planeX, planeN)); + + float projPivot = dot(planeN, pivotToCam); + float projVertex = dot(planeN, vertexToCam); + float ratio = projPivot / projVertex; + + float3 offset = vertexToCam * ratio - pivotToCam; + + float2 uv = float2(dot(planeX, offset), dot(planeY, offset)); + uv /= (2.0f * size); + uv *= -1.0f; + uv += 0.5; + return uv; +} + struct appdata { float4 vertex : POSITION; UNITY_VERTEX_INPUT_INSTANCE_ID @@ -58,10 +90,15 @@ struct v2f { V2F_SHADOW_CASTER; #else float4 pos : SV_POSITION; - UNITY_FOG_COORDS(3) + UNITY_FOG_COORDS(7) #endif - float2 uv : TEXCOORD1; - float2 cell : TEXCOORD2; + float2 uv1 : TEXCOORD1; + float2 uv2 : TEXCOORD2; + float2 uv3 : TEXCOORD3; + nointerpolation float2 cell1 : TEXCOORD4; + nointerpolation float2 cell2 : TEXCOORD5; + nointerpolation float2 cell3 : TEXCOORD6; + float3 blendWeights : TEXCOORD8; UNITY_VERTEX_OUTPUT_STEREO }; @@ -82,44 +119,83 @@ v2f vert(appdata v) { float3 camPos = _WorldSpaceCameraPos; #endif + // View direction in object space float3 viewOS = normalize(mul((float3x3)unity_WorldToObject, normalize(camPos - center))); - int2 cell = GetCell(viewOS); - float3 snapOS = CellDir(cell); - float3 snapWS = normalize(mul((float3x3)unity_ObjectToWorld, snapOS)); + // Get continuous grid position and find the 3 frames + float gridRes = (float)_GridResolution; + float2 grid = GridFromDir(viewOS, gridRes); + float2 gridFloor = floor(grid); + float2 gridFrac = frac(grid); + + // Compute blend weights and determine which triangle + float4 weights = QuadBlendWeights(gridFrac); + o.blendWeights = weights.xyz; + + // Frame 1: base corner + o.cell1 = gridFloor; + + // Frame 2: depends on which triangle (lower-left vs upper-right) + // weights.w = 0: lower-left triangle -> (0,1) offset + // weights.w = 1: upper-right triangle -> (1,0) offset + o.cell2 = clamp(gridFloor + lerp(float2(0,1), float2(1,0), weights.w), 0, gridRes - 1); + + // Frame 3: diagonal corner + o.cell3 = clamp(gridFloor + float2(1,1), 0, gridRes - 1); + + // Get directions for each frame + float3 dir1 = DirFromCell(o.cell1, gridRes); + float3 dir2 = DirFromCell(o.cell2, gridRes); + float3 dir3 = DirFromCell(o.cell3, gridRes); + + // Billboard facing the camera direction (not snapped) + float3 viewWS = normalize(camPos - center); float3 right, up; - BillboardBasis(snapWS, right, up); + BillboardBasis(viewWS, right, up); float3 worldPos = center + v.vertex.x * right * scale.x + v.vertex.y * up * scale.y; #ifdef IMPOSTOR_SHADOW_PASS v.vertex = mul(unity_WorldToObject, float4(worldPos, 1)); - v.normal = -snapWS; + v.normal = -viewWS; TRANSFER_SHADOW_CASTER_NORMALOFFSET(o) #else o.pos = mul(UNITY_MATRIX_VP, float4(worldPos, 1)); UNITY_TRANSFER_FOG(o, o.pos); #endif - float3 localOff = mul((float3x3)unity_WorldToObject, worldPos - center); - BillboardBasis(snapOS, right, up); - o.uv = float2(1 - (dot(localOff, right) + 0.5), dot(localOff, up) + 0.5); - o.cell = float2(cell); + // Compute virtual plane UVs for all 3 frames + // pivotToCam and vertexToCam in object space + float3 pivotToCamOS = mul((float3x3)unity_WorldToObject, camPos - center); + float3 vertexPosOS = mul((float3x3)unity_WorldToObject, worldPos - center); + float3 vertexToCamOS = pivotToCamOS - vertexPosOS; + + // size = 0.5 because the mesh is a unit quad (-0.5 to 0.5) + o.uv1 = VirtualPlaneUV(dir1, pivotToCamOS, vertexToCamOS, 0.5); + o.uv2 = VirtualPlaneUV(dir2, pivotToCamOS, vertexToCamOS, 0.5); + o.uv3 = VirtualPlaneUV(dir3, pivotToCamOS, vertexToCamOS, 0.5); return o; } +float4 BlendFrames(v2f i) { + float4 s1 = SampleAtlas(i.uv1, i.cell1); + float4 s2 = SampleAtlas(i.uv2, i.cell2); + float4 s3 = SampleAtlas(i.uv3, i.cell3); + return s1 * i.blendWeights.x + s2 * i.blendWeights.y + s3 * i.blendWeights.z; +} + #ifdef IMPOSTOR_SHADOW_PASS float4 frag(v2f i) : SV_Target { - float4 col = SampleAtlas(i.uv, i.cell); + float4 col = BlendFrames(i); clip(col.a - _Cutoff); SHADOW_CASTER_FRAGMENT(i) } #else float4 frag(v2f i) : SV_Target { - float4 col = SampleAtlas(i.uv, i.cell); + float4 col = BlendFrames(i); if (_DebugMode > 0.5) - return float4(i.uv, 0, 1); + return float4(i.blendWeights.xy, 0, 1); col *= _Color; clip(col.a - _Cutoff); |