c31: Start sketching tangent space raymarcher

1 files changed, 54 insertions, 0 deletions

diff --git a/custom31.cginc b/custom31.cginc
new file mode 100644
index 0000000..6f29403
--- /dev/null
+++ b/custom31.cginc
@@ -0,0 +1,54 @@
+#ifndef __CUSTOM31_INC
+#define __CUSTOM31_INC
+
+#include "globals.cginc"
+#include "interpolators.cginc"
+
+float map(float3 p) {
+  return length(p) - 0.1;
+}
+
+void apply_custom31_world(v2f i, inout Pbr pbr, inout float3 normal_tangent) {
+#if defined(_CUSTOM31_WORLD)
+  // We will raymarch in (tangent, binormal, normal) coordinates.
+  // Make an expanded homogeneous tbn matrix to support moving back and forth.
+  // This first incarnation moves from world to tangent.
+  float4x4 tbn = float4x4(
+      pbr.tbn[0], 0,
+      pbr.tbn[1], 0,
+      pbr.tbn[2], 0,
+      0, 0, 0,    1);
+  tbn = mul(tbn, unity_WorldToObject);
+
+  float3 ro = mul(tbn, float4(i.worldPos, 1));
+  float3 rd = normalize(mul((float3x3) tbn, i.worldPos - _WorldSpaceCameraPos));
+
+  float d_acc = 0;
+  float d;
+  const float MIN_DIST = 1e-3;
+  const float MAX_DIST = 1;
+  [loop]
+  for (uint ii = 0; ii < 10; ++ii) {
+    float3 p = ro + rd * d_acc;
+    d = map(p);
+    d_acc += d;
+    if (d < MIN_DIST) {
+      break;
+    }
+    if (d > MAX_DIST) {
+      break;
+    }
+  }
+
+  if (d < MIN_DIST) {
+    pbr.albedo.xyz = 1;
+  } else {
+    pbr.albedo.xyz = 0;
+  }
+
+  float3 p = ro + rd * d_acc;
+  p = mul(float4(p, 1), tbn);
+#endif
+}
+
+#endif  // __CUSTOM31_INC