add machinery for multiple uv channels

1 files changed, 32 insertions, 0 deletions

diff --git a/texture_utils.cginc b/texture_utils.cginc
new file mode 100644
index 0000000..9d7bf2f
--- /dev/null
+++ b/texture_utils.cginc
@@ -0,0 +1,32 @@
+#ifndef __TEXTURE_UTILS_INC
+#define __TEXTURE_UTILS_INC
+
+#include "interpolators.cginc"
+
+float2 get_uv_by_channel(v2f i, uint which_channel) {
+  [forcecase]
+  switch (which_channel) {
+    case 0:
+      return i.uv01.xy;
+      break;
+    case 1:
+      return i.uv01.zw;
+      break;
+    case 2:
+      return i.uv23.xy;
+      break;
+    case 3:
+      return i.uv23.zw;
+      break;
+    default:
+      return 0;
+      break;
+  }
+}
+
+#define UV_SCOFF_IMPL(uv, tex_st) (uv) * (tex_st).xy + (tex_st).zw
+
+#define UV_SCOFF(i, tex_st, which_channel) UV_SCOFF_IMPL(get_uv_by_channel(i, round(which_channel)), tex_st)
+
+#endif  // __TEXTURE_UTILS_INC
+