shitty ai code, preparing to rewrite

2 files changed, 36 insertions, 35 deletions

diff --git a/3ner.shader b/3ner.shader
index 249f02b..bb14f24 100644
--- a/3ner.shader
+++ b/3ner.shader
@@ -209,7 +209,7 @@ Shader "yum_food/3ner"
               [ThryToggle(_VERTEX_DEFORMATION_XZ_TUBE)] _Vertex_Deformation_XZ_Tube_Enabled("Enable", Float) = 0
               _Vertex_Deformation_XZ_Tube_p("p", Vector) = (0, 0, 1)
               _Vertex_Deformation_XZ_Tube_r("r", Vector) = (0, 0, -1)
-              _Vertex_Deformation_XZ_Tube_r("s", Vector) = (0, 0, -1)
+              _Vertex_Deformation_XZ_Tube_s("s", Vector) = (0, 0, -1)
               _Vertex_Deformation_XZ_Tube_t("t", Range(-1,1)) = 0
             [HideInInspector] m_end_Vertex_Deformation_XZ_Tube("XZ Tube", Float) = 0
             //endex
diff --git a/vertex_deformation.slang b/vertex_deformation.slang
index f22e71f..dc77516 100644
--- a/vertex_deformation.slang
+++ b/vertex_deformation.slang
@@ -94,50 +94,51 @@ float2 project_x_onto_y(float2 x, float2 y) {
 // Maps a 2x2 quad on the xy plane to a tube. The circular cross section
 // is on the xz plane.
 [Differentiable]
-public float3 plane_to_tube(float3 xyz, no_diff float3 p, no_diff float3 r, no_diff float3 s, no_diff float t) {
-  xyz = 0;
+public float3 plane_to_tube(float3 xyz,
+    no_diff float3 p, no_diff float3 r_cart, no_diff float3 s_cart, no_diff float t) {
   // Convert from cartesian to (r, s, r x s) space.
   // Ensure orthonormal basis vectors.
   // TODO remove normalize, do at higher level of stack.
-  r = normalize(r);
-  s = normalize(s);
-  float3 rxs = cross(r, s);
-  float3x3 to_rsrxs = transpose(float3x3(r, s, rxs));
+  r_cart = normalize(r_cart);
+  s_cart = normalize(s_cart);
+  float3 rxs_cart = cross(s_cart, r_cart);
+  float3x3 to_rsrxs = transpose(float3x3(r_cart, s_cart, rxs_cart));
   float3x3 to_cart  = inverse(to_rsrxs, determinant(to_rsrxs));
 
   // Translate origin to `p` then change into (r, s, r x s) basis.
   xyz = mul(to_rsrxs, xyz - p);
 
-  // Project onto (r, r x s) plane.
-  float2 v0 = xyz.xz;
-
-  float2 v0_hat = normalize(v0);
-  float2 Lr  = float2(v0.x, 0);
-  float2 Lv0 = float2(0, v0.y);
-  float Lr_norm  = abs(Lr.x);
-  float Lv0_norm = abs(Lv0.y);
-  float epsilon = 1e-4;
-  float theta = Lv0_norm / (Lr_norm + epsilon);
-  float phi = atan2(Lv0_norm, Lr_norm);
-  float theta_p = lerp(theta, phi, t);
-  float2x2 rot = float2x2(
-      cos(theta_p), -sin(theta_p),
-      sin(theta_p),  cos(theta_p));
-
-  // float2(1, 0) is written as `r` in (2) in the notes. We just rewrite it
-  // here since we're in the rotated frame.
-  // We also don't have to add p since again we're in the rotated and
-  // translated frame.
-  float2 v = mul(rot, dlerp(float2(1, 0) * Lv0_norm, Lr, t));
-
-  // Un-project.
-  xyz.xz = v.xy;
+  // Components in pivot basis: n (neutral axis), b (tangential), h (axial s).
+  float epsilon = 1e-4f;
+  float r = xyz.x;     // neutral-axis coordinate
+  float s = xyz.y;     // axial coordinate along s_cart
+  float rxs = xyz.z;   // tangential coordinate along rxs_cart
 
-  // Move back into cartesian basis.
-  xyz = mul(to_cart, xyz);
+  float r0 = length(float2(r, rxs));     // |(r, rxs)| at identity
+  float r1 = max(abs(r), epsilon);       // target radius |r|
+
+  // Directions for identity and wrapped states in the (n, b) plane.
+  float2 dir0 = float2(r, rxs) / max(r0, epsilon);
+  float theta_wrap = rxs / r1;           // theta = w / r per derivation
+  float signish = r / r1;                // preserves sign of r without branch
+  float2 dir1 = float2(signish * cos(theta_wrap), sin(theta_wrap));
+
+  // Shortest-arc angular blend (delta = atan2(cross, dot)) without branchy conditionals.
+  float dot01 = clamp(dot(dir0, dir1), -1.0f, 1.0f);
+  float cross01 = dir0.x * dir1.y - dir0.y * dir1.x;
+  float delta = atan2(cross01, dot01);
+  float theta0 = atan2(dir0.y, dir0.x);
+  float theta_p = theta0 + t * delta;
 
-  // Translate p back away from origin.
-  xyz += p;
+  // Radial interpolation per derivation.
+  float radius = dlerp(r0, r1, t);
+  float2 nb_t = float2(cos(theta_p), sin(theta_p)) * radius;
+
+  // Reconstruct with preserved axial component.
+  xyz = float3(nb_t.x, s, nb_t.y);
+
+  // Move back into cartesian basis.
+  xyz = mul(to_cart, xyz) + p;
 
   return xyz;
 }