more stuff

1 files changed, 70 insertions, 0 deletions

diff --git a/example.slang b/example.slang
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index 0000000..b87e1bb
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+++ b/example.slang
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+#ifndef __EXAMPLE_INC
+#define __EXAMPLE_INC
+
+float3x3 inverse(float3x3 m) {
+  float det =
+    m._11 * (m._22 * m._33 - m._23 * m._32) -
+    m._12 * (m._21 * m._33 - m._23 * m._31) +
+    m._13 * (m._21 * m._32 - m._22 * m._31);
+
+  if (abs(det) < 1e-6) {
+    return float3x3(
+        1,0,0,
+        0,1,0,
+        0,0,1);
+  }
+
+  float invDet = 1.0f / det;
+  float3x3 inv;
+
+  inv._11 = (m._22 * m._33 - m._23 * m._32) * invDet;
+  inv._12 = (m._13 * m._32 - m._12 * m._33) * invDet;
+  inv._13 = (m._12 * m._23 - m._13 * m._22) * invDet;
+  inv._21 = (m._23 * m._31 - m._21 * m._33) * invDet;
+  inv._22 = (m._11 * m._33 - m._13 * m._31) * invDet;
+  inv._23 = (m._13 * m._21 - m._11 * m._23) * invDet;
+  inv._31 = (m._21 * m._32 - m._22 * m._31) * invDet;
+  inv._32 = (m._31 * m._12 - m._11 * m._32) * invDet;
+  inv._33 = (m._11 * m._22 - m._12 * m._21) * invDet;
+
+  return inv;
+}
+
+#define PI 3.14159265f
+
+[Differentiable]
+public float3 ex_deform(float3 xyz, no_diff float A, no_diff float k, no_diff float t) {
+  float x = xyz.x;
+  float y = xyz.y;
+  float z = xyz.z;
+  return float3(
+    x + sin(y * k) * 0.1,
+    y + sin(x * k * 4) * 0.5,
+    (z + sin(x * y * k * PI + t) * A) * (1.0 + sin(y * k) * sin(x * k))
+  );
+}
+
+// Deform a normal vector using the inverse transpose of the jacobian.
+public void ex_deform_normal(float3 xyz, inout float3 normal, inout float3 tangent, float A, float k, float t) {
+  // Compute jacobian using autodiff applied to basis vectors.
+  DifferentialPair<float3> dp_x = diffPair(xyz, float3(1, 0, 0));
+  DifferentialPair<float3> dp_y = diffPair(xyz, float3(0, 1, 0));
+  DifferentialPair<float3> dp_z = diffPair(xyz, float3(0, 0, 1));
+
+  DifferentialPair<float3> dp_x_out = fwd_diff(ex_deform)(dp_x, A, k, t);
+  DifferentialPair<float3> dp_y_out = fwd_diff(ex_deform)(dp_y, A, k, t);
+  DifferentialPair<float3> dp_z_out = fwd_diff(ex_deform)(dp_z, A, k, t);
+
+  // Transform normal and tangent using jacobian
+  float3x3 jacobian = float3x3(
+    float3(dp_x_out.d.x, dp_y_out.d.x, dp_z_out.d.x),
+    float3(dp_x_out.d.y, dp_y_out.d.y, dp_z_out.d.y),
+    float3(dp_x_out.d.z, dp_y_out.d.z, dp_z_out.d.z)
+  );
+  float3x3 itjac = inverse(transpose(jacobian));
+  normal = normalize(mul(itjac, normal));
+  tangent = normalize(mul(jacobian, tangent));
+}
+
+#endif  // __EXAMPLE_INC
+