perf(render3d): the terrain's height and normal in R32F + RG16F, 128 MB where one RGBA32F was 256

The first generation pass's R32F height is kept as ter_height_tex (not copied into an RGBA32F),
so every reader of the height - placement, the read-back, physics, selftest16's 9 mm - sees the
same 32 bits. ternormal.frag writes the baked normal's x and z into ter_normal_tex (RG16F), and
the six places that read it (terrain.frag twice, tersun.frag, grass.vert, grass.mesh,
grass_cull.comp, which takes a third texture at binding 6) rebuild y. SPIR-V regenerated.

Maroon Lake's play, headless Vulkan: 2793 -> 2647 MB. The camp's frame: 0.066% of pixels differ by
more than 8 (mean 0.024/255), isolated grass blades at the slope gate. ludic-dev test 307/307.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.render3d/shaders/grass.mesh

@@ -17,6 +17,9 @@ uniform mat4 u_vp;
 uniform vec3 u_cam_pos;
 uniform float u_time;
 uniform sampler2D u_ts_height;
+// the baked terrain normal: x and z in RG16F, y rebuilt (a terrain normal always points up)
+uniform sampler2D u_ter_normal;
+vec3 terNormal(vec2 uv) { vec2 xz = textureLod(u_ter_normal, uv, 0.0).rg;  return vec3(xz.x, sqrt(max(1.0 - dot(xz, xz), 0.0)), xz.y); }
 uniform vec2 u_ts_origin;
 uniform float u_ts_half;
 uniform sampler2D u_ortho;
@@ -95,7 +98,7 @@ void main() {
     vec4 ht = textureLod(u_ts_height, huv, 0.0);
     vec4 croot = u_vp * vec4(xz.x, ht.r, xz.y, 1.0);
     if (croot.w < -1.0 || abs(croot.x) > croot.w * 1.25 + 1.5 || abs(croot.y) > croot.w * 1.4 + 1.5) continue;
-    vec3 gn = normalize(ht.gba);
+    vec3 gn = terNormal(huv);
     float h3 = bladeHash(ci, j, 2), h4 = bladeHash(ci, j, 3);
     float wl = u_sea_level;
     if (u_lake.z > 0.0) { vec2 q = (xz - u_lake.xy) / u_lake.zw;  if (dot(q, q) < 1.0) wl = max(wl, u_lake_level); }

packages/ludic.render3d/shaders/grass.vert

@@ -15,6 +15,9 @@ uniform mat4 u_vp;
 uniform vec3 u_cam_pos;
 uniform float u_time;
 uniform sampler2D u_ts_height;
+// the baked terrain normal: x and z in RG16F, y rebuilt (a terrain normal always points up)
+uniform sampler2D u_ter_normal;
+vec3 terNormal(vec2 uv) { vec2 xz = textureLod(u_ter_normal, uv, 0.0).rg;  return vec3(xz.x, sqrt(max(1.0 - dot(xz, xz), 0.0)), xz.y); }
 uniform vec2 u_ts_origin;
 uniform float u_ts_half;
 uniform sampler2D u_ortho;
@@ -133,7 +136,7 @@ void main() {
   vec4 ht = texture(u_ts_height, huv);
   vec4 croot = u_vp * vec4(xz.x, ht.r, xz.y, 1.0);
   if (croot.w < -1.0 || abs(croot.x) > croot.w * 1.25 + 1.5 || abs(croot.y) > croot.w * 1.4 + 1.5) { cull(); return; }
-  vec3 gn = normalize(ht.gba);
+  vec3 gn = terNormal(huv);
   float h3 = bladeHash(ci, j, 2), h4 = bladeHash(ci, j, 3);
   // No blades under water: the sea's line everywhere, and the lake's inside its outline. One
   // line for both left a lake above the sea with grass on its bed or a valley with none.

packages/ludic.render3d/shaders/grass_cull.comp

@@ -25,8 +25,9 @@ layout(set = 0, binding = 0) uniform Params {
 layout(set = 0, binding = 1) readonly buffer Tiles { vec4 tiles[]; };   // corner x/z, indices per cell, cells per side
 layout(set = 0, binding = 2) buffer Out { vec4 outv[]; };               // 4 per blade
 layout(set = 0, binding = 3) buffer Cmds { uint cmds[]; };              // VkDrawIndexedIndirectCommand per band
-layout(set = 0, binding = 4) uniform sampler2D u_height;                // height, normal (terrain's u_ts_height)
+layout(set = 0, binding = 4) uniform sampler2D u_height;                // the height (terrain's u_ts_height)
 layout(set = 0, binding = 5) uniform sampler2D u_ortho;                 // the photograph
+layout(set = 0, binding = 6) uniform sampler2D u_ter_normal;            // the normal: x and z, y rebuilt
 
 const float CELL = 4.0;   // grass.ludic GRASS_CELL
 
@@ -92,7 +93,8 @@ void main() {
   // the frustum, on a sphere round the blade (it stands at most 0.9 m tall)
   vec3 root = vec3(xz.x, ht.r, xz.y);
   for (int k = 0; k < 4; k++) { if (dot(pr.planes[k].xyz, root) + pr.planes[k].w < -1.0) return; }
-  vec3 gn = normalize(ht.gba);
+  vec2 gxz = textureLod(u_ter_normal, huv, 0.0).rg;
+  vec3 gn = vec3(gxz.x, sqrt(max(1.0 - dot(gxz, gxz), 0.0)), gxz.y);
   float h3 = bladeHash(ci, j, 2), h4 = bladeHash(ci, j, 3);
   float wl = pr.lev.y;
   if (pr.lake.z > 0.0) { vec2 q = (xz - pr.lake.xy) / pr.lake.zw;  if (dot(q, q) < 1.0) wl = max(wl, pr.lev.x); }

packages/ludic.render3d/shaders/spv/manifest.txt

@@ -918,8 +918,9 @@ T d48d6a48 u_nrm 7
 T d48d6a48 u_ortho 8
 T d48d6a48 u_prefilter 9
 T d48d6a48 u_shadow 10
-T d48d6a48 u_tershadow 11
-T d48d6a48 u_ts_height 12
+T d48d6a48 u_ter_normal 11
+T d48d6a48 u_tershadow 12
+T d48d6a48 u_ts_height 13
 P cb13f3c6 grass.vert model.frag #define FOLIAGE;#define BLADE;#define GBLADE;
 B cb13f3c6 vert 0 324
 U cb13f3c6 vert u_view 0 mat4 1 0
@@ -1000,8 +1001,9 @@ T cb13f3c6 u_nrm 7
 T cb13f3c6 u_ortho 8
 T cb13f3c6 u_prefilter 9
 T cb13f3c6 u_shadow 10
-T cb13f3c6 u_tershadow 11
-T cb13f3c6 u_ts_height 12
+T cb13f3c6 u_ter_normal 11
+T cb13f3c6 u_tershadow 12
+T cb13f3c6 u_ts_height 13
 P b8cff226 grass.vert model.frag #define FOLIAGE;#define BLADE;#define GBLADE;#define TILES;
 B b8cff226 vert 0 4420
 U b8cff226 vert u_view 0 mat4 1 0
@@ -1083,8 +1085,9 @@ T b8cff226 u_nrm 7
 T b8cff226 u_ortho 8
 T b8cff226 u_prefilter 9
 T b8cff226 u_shadow 10
-T b8cff226 u_tershadow 11
-T b8cff226 u_ts_height 12
+T b8cff226 u_ter_normal 11
+T b8cff226 u_tershadow 12
+T b8cff226 u_ts_height 13
 P 3733fc38 impostor.vert impostor.frag 
 B 3733fc38 vert 0 232
 U 3733fc38 vert u_view 0 mat4 1 0
@@ -3020,8 +3023,9 @@ T 2e2908c8 u_rock_n 13
 T 2e2908c8 u_shadow 14
 T 2e2908c8 u_snow_d 15
 T 2e2908c8 u_sunshadow 16
-T 2e2908c8 u_tershadow 17
-T 2e2908c8 u_ts_height 18
+T 2e2908c8 u_ter_normal 17
+T 2e2908c8 u_tershadow 18
+T 2e2908c8 u_ts_height 19
 P 1f95f31b terrain.vert terrain.frag #define FAR_ONLY;
 B 1f95f31b vert 0 204
 U 1f95f31b vert u_half 0 float 1 0
@@ -3097,8 +3101,9 @@ T 1f95f31b u_rock_n 13
 T 1f95f31b u_shadow 14
 T 1f95f31b u_snow_d 15
 T 1f95f31b u_sunshadow 16
-T 1f95f31b u_tershadow 17
-T 1f95f31b u_ts_height 18
+T 1f95f31b u_ter_normal 17
+T 1f95f31b u_tershadow 18
+T 1f95f31b u_ts_height 19
 P f4382918 terrain.vert terrain.frag #define NEAR_ONLY;
 B f4382918 vert 0 204
 U f4382918 vert u_half 0 float 1 0
@@ -3174,8 +3179,9 @@ T f4382918 u_rock_n 13
 T f4382918 u_shadow 14
 T f4382918 u_snow_d 15
 T f4382918 u_sunshadow 16
-T f4382918 u_tershadow 17
-T f4382918 u_ts_height 18
+T f4382918 u_ter_normal 17
+T f4382918 u_tershadow 18
+T f4382918 u_ts_height 19
 P f2952361 terrain.vert terrain.frag #define SUN_INLINE;
 B f2952361 vert 0 204
 U f2952361 vert u_half 0 float 1 0
@@ -3251,8 +3257,9 @@ T f2952361 u_rock_n 13
 T f2952361 u_shadow 14
 T f2952361 u_snow_d 15
 T f2952361 u_sunshadow 16
-T f2952361 u_tershadow 17
-T f2952361 u_ts_height 18
+T f2952361 u_ter_normal 17
+T f2952361 u_tershadow 18
+T f2952361 u_ts_height 19
 P a0f2dbac terrain.vert terrain.frag #define SUN_INLINE;#define FAR_ONLY;
 B a0f2dbac vert 0 204
 U a0f2dbac vert u_half 0 float 1 0
@@ -3328,8 +3335,9 @@ T a0f2dbac u_rock_n 13
 T a0f2dbac u_shadow 14
 T a0f2dbac u_snow_d 15
 T a0f2dbac u_sunshadow 16
-T a0f2dbac u_tershadow 17
-T a0f2dbac u_ts_height 18
+T a0f2dbac u_ter_normal 17
+T a0f2dbac u_tershadow 18
+T a0f2dbac u_ts_height 19
 P 5e4589a1 terrain.vert terrain.frag #define SUN_INLINE;#define NEAR_ONLY;
 B 5e4589a1 vert 0 204
 U 5e4589a1 vert u_half 0 float 1 0
@@ -3405,8 +3413,9 @@ T 5e4589a1 u_rock_n 13
 T 5e4589a1 u_shadow 14
 T 5e4589a1 u_snow_d 15
 T 5e4589a1 u_sunshadow 16
-T 5e4589a1 u_tershadow 17
-T 5e4589a1 u_ts_height 18
+T 5e4589a1 u_ter_normal 17
+T 5e4589a1 u_tershadow 18
+T 5e4589a1 u_ts_height 19
 P bf3151c8 terrain.vert tersun.frag 
 B bf3151c8 vert 0 204
 U bf3151c8 vert u_half 0 float 1 0
@@ -3462,8 +3471,9 @@ T bf3151c8 u_height 3
 T bf3151c8 u_irradiance 4
 T bf3151c8 u_prefilter 5
 T bf3151c8 u_shadow 6
-T bf3151c8 u_tershadow 7
-T bf3151c8 u_ts_height 8
+T bf3151c8 u_ter_normal 7
+T bf3151c8 u_tershadow 8
+T bf3151c8 u_ts_height 9
 P 46e2325c water.vert water.frag 
 B 46e2325c vert 0 152
 U 46e2325c vert u_view 0 mat4 1 0

packages/ludic.render3d/shaders/ternormal.frag

@@ -1,5 +1,5 @@
-// Second generation pass: copy the height into R and bake the B-spline surface normal into
-// GBA, once, at texel resolution. terrain.frag used to differentiate the bicubic height
+// Second generation pass: bake the B-spline surface normal, once, at texel resolution: x and z
+// into an RG16F beside the R32F height (y is rebuilt where it is read). terrain.frag used to differentiate the bicubic height
 // per pixel — four bicubic reads, sixteen taps — for a quantity that never changes.
 in vec2 v_uv;
 out vec4 o;
@@ -28,5 +28,5 @@ void main() {
   float hd = heightSmooth(u_src, v_uv - vec2(0, step));
   float hu = heightSmooth(u_src, v_uv + vec2(0, step));
   vec3 n = normalize(vec3(hl - hr, 2.0 * world, hd - hu));
-  o = vec4(texture(u_src, v_uv).r, n);
+  o = vec4(n.x, n.z, 0.0, 0.0);      // into RG16F: x and z, y rebuilt when read (always up)
 }

packages/ludic.render3d/shaders/terrain.frag

@@ -7,6 +7,9 @@ out vec4 o_color;
 #define gnoise(p) 0.1
 #endif
 uniform sampler2D u_height;
+// the baked terrain normal: x and z in RG16F, y rebuilt (a terrain normal always points up)
+uniform sampler2D u_ter_normal;
+vec3 terNormal(vec2 uv) { vec2 xz = texture(u_ter_normal, uv).rg;  return vec3(xz.x, sqrt(max(1.0 - dot(xz, xz), 0.0)), xz.y); }
 uniform float u_half;
 uniform float u_texel;               // height-map texel size in uv
 uniform sampler2D u_grass_d; uniform sampler2D u_grass_n; uniform sampler2D u_grass_a;
@@ -76,7 +79,7 @@ float heightSmooth(sampler2D tex, vec2 uv) {
 }
 // baked at generation (ternormal.frag) into the height texture's GBA
 vec3 terrainNormal(vec2 uv) {
-  return normalize(texture(u_height, uv).gba);
+  return terNormal(uv);
 }
 
 // stochastic (triangle-grid) sampling: three randomly offset / rotated taps blended by
@@ -223,7 +226,7 @@ void triC(bool cheap, sampler2D d, sampler2D nm, sampler2D am, vec3 p, vec3 dpx,
 uniform float u_far_split;
 uniform float u_far_band;
 float sunInline(vec3 p, float dist, float viewDepth) {
-  vec3 Ng = normalize(texture(u_height, v_huv).gba);
+  vec3 Ng = terNormal(v_huv);
   if (dist > u_far_split + u_far_band) return sunShadowCheap(p, Ng, viewDepth);
   if (dist < u_far_split - u_far_band) return sunShadow(p, Ng, viewDepth);
   return mix(sunShadow(p, Ng, viewDepth), sunShadowCheap(p, Ng, viewDepth),

packages/ludic.render3d/shaders/tersun.frag

@@ -12,13 +12,16 @@ in vec3 v_wpos;
 in vec2 v_huv;
 out float o_sh;
 uniform sampler2D u_height;
+// the baked terrain normal: x and z in RG16F, y rebuilt (a terrain normal always points up)
+uniform sampler2D u_ter_normal;
+vec3 terNormal(vec2 uv) { vec2 xz = texture(u_ter_normal, uv).rg;  return vec3(xz.x, sqrt(max(1.0 - dot(xz, xz), 0.0)), xz.y); }
 uniform mat4 u_view;
 uniform float u_far_split;
 uniform float u_far_band;
 void main() {
   vec3 p = v_wpos;
   if (p.y < u_clip_y) discard;
-  vec3 N = normalize(texture(u_height, v_huv).gba);
+  vec3 N = terNormal(v_huv);
   float dist = length(p - u_cam_pos);
   float viewDepth = -(u_view * vec4(p, 1.0)).z;
   // The same tier choice the ground makes, cross-faded over the same band: the near tier