initial check-in
diff --git a/progs/demos/shadow.h b/progs/demos/shadow.h
new file mode 100644
index 0000000..b19dd43
--- /dev/null
+++ b/progs/demos/shadow.h
@@ -0,0 +1,18 @@
+#ifndef SHADOW_H
+#define SHADOW_H
+
+
+extern void
+shadowmatrix(GLfloat shadowMat[4][4],
+             GLfloat groundplane[4],
+             GLfloat lightpos[4]);
+
+
+extern void
+findplane(GLfloat plane[4],
+          GLfloat v0[3], GLfloat v1[3], GLfloat v2[3]);
+
+
+#endif
+
+