keep the normal transforms in float during skinning

FIXES=[342459864]

NEW_RELEASE_NOTES.md

@@ -7,3 +7,5 @@ for next branch cut* header.
 appropriate header in [RELEASE_NOTES.md](./RELEASE_NOTES.md).
 
 ## Release notes for next branch cut
+
+- engine: fix skinning normals with large transforms (b/342459864) [⚠️ **New Material Version**]

filament/src/details/SkinningBuffer.cpp

@@ -114,6 +114,7 @@ void FSkinningBuffer::setBones(FEngine& engine,
     setBones(engine, mHandle, transforms, count, offset);
 }
 
+UTILS_UNUSED
 static uint32_t packHalf2x16(half2 v) noexcept {
     uint32_t lo = getBits(v[0]);
     uint32_t hi = getBits(v[1]);
@@ -144,13 +145,8 @@ PerRenderableBoneUib::BoneData FSkinningBuffer::makeBone(mat4f transform) noexce
                     transform[1],
                     transform[2]
             },
-            .cof = {
-                    packHalf2x16({ cofactors[0].x, cofactors[0].y }),
-                    packHalf2x16({ cofactors[0].z, cofactors[1].x }),
-                    packHalf2x16({ cofactors[1].y, cofactors[1].z }),
-                    packHalf2x16({ cofactors[2].x, cofactors[2].y })
-                    // cofactor[2][2] is not stored because we don't have space for it
-            }
+            .cof0 = cofactors[0],
+            .cof1x = cofactors[1].x
     };
 }
 

libs/filabridge/include/filament/MaterialEnums.h

@@ -28,7 +28,7 @@
 namespace filament {
 
 // update this when a new version of filament wouldn't work with older materials
-static constexpr size_t MATERIAL_VERSION = 52;
+static constexpr size_t MATERIAL_VERSION = 53;
 
 /**
  * Supported shading models

libs/filabridge/include/private/filament/UibStructs.h

@@ -327,8 +327,9 @@ struct PerRenderableBoneUib { // NOLINT(cppcoreguidelines-pro-type-member-init)
     struct alignas(16) BoneData {
         // bone transform, last row assumed [0,0,0,1]
         math::float4 transform[3];
-        // 8 first cofactor matrix of transform's upper left
-        math::uint4 cof;
+        // 4 first cofactor matrix of transform's upper left
+        math::float3 cof0;
+        float cof1x;
     };
     BoneData bones[CONFIG_MAX_BONE_COUNT];
 };

shaders/src/common_types.glsl

@@ -19,7 +19,8 @@ struct ShadowData {
 #if defined(VARIANT_HAS_SKINNING_OR_MORPHING)
 struct BoneData {
     highp mat3x4 transform;    // bone transform is mat4x3 stored in row-major (last row [0,0,0,1])
-    highp uvec4 cof;           // 8 first cofactor matrix of transform's upper left
+    highp float3 cof0;         // 3 first cofactor matrix of transform's upper left
+    highp float cof1x;         // 4th cofactor
 };
 #endif
 

shaders/src/getters.vs

@@ -34,25 +34,32 @@ int getVertexIndex() {
 
 #if defined(VARIANT_HAS_SKINNING_OR_MORPHING)
 #define MAX_SKINNING_BUFFER_WIDTH 2048u
-vec3 mulBoneNormal(vec3 n, uint i) {
+vec3 mulBoneNormal(vec3 n, uint j) {
 
     highp mat3 cof;
 
-    // the first 8 elements of the cofactor matrix are stored as fp16
-    highp vec2 x0y0 = unpackHalf2x16(bonesUniforms.bones[i].cof[0]);
-    highp vec2 z0x1 = unpackHalf2x16(bonesUniforms.bones[i].cof[1]);
-    highp vec2 y1z1 = unpackHalf2x16(bonesUniforms.bones[i].cof[2]);
-    highp vec2 x2y2 = unpackHalf2x16(bonesUniforms.bones[i].cof[3]);
-
     // the last element must be computed by hand
-    highp float a = bonesUniforms.bones[i].transform[0][0];
-    highp float b = bonesUniforms.bones[i].transform[0][1];
-    highp float d = bonesUniforms.bones[i].transform[1][0];
-    highp float e = bonesUniforms.bones[i].transform[1][1];
+    highp float a = bonesUniforms.bones[j].transform[0][0];
+    highp float b = bonesUniforms.bones[j].transform[0][1];
+    highp float c = bonesUniforms.bones[j].transform[0][2];
+    highp float d = bonesUniforms.bones[j].transform[1][0];
+    highp float e = bonesUniforms.bones[j].transform[1][1];
+    highp float f = bonesUniforms.bones[j].transform[1][2];
+    highp float g = bonesUniforms.bones[j].transform[2][0];
+    highp float h = bonesUniforms.bones[j].transform[2][1];
+    highp float i = bonesUniforms.bones[j].transform[2][2];
 
-    cof[0].xyz = vec3(x0y0, z0x1.x);
-    cof[1].xyz = vec3(z0x1.y, y1z1);
-    cof[2].xyz = vec3(x2y2, a * e - b * d);
+    cof[0] = bonesUniforms.bones[j].cof0;
+
+    cof[1].xyz = vec3(
+            bonesUniforms.bones[j].cof1x,
+            a * i - c * g,
+            c * d - a * f);
+
+    cof[2].xyz = vec3(
+            d * h - e * g,
+            b * g - a * h,
+            a * e - b * d);
 
     return normalize(cof * n);
 }