+/**
+ * Check if X, Y or Z component of the coordinate is close to W, in terms
+ * of the clip test.
+ */
+static GLboolean
+xyz_close_to_w(const GLfloat c[4])
+{
+ float k = 0.0001;
+ return (fabs(c[0] - c[3]) < k ||
+ fabs(c[1] - c[3]) < k ||
+ fabs(c[2] - c[3]) < k ||
+ fabs(-c[0] - c[3]) < k ||
+ fabs(-c[1] - c[3]) < k ||
+ fabs(-c[2] - c[3]) < k);
+}
+
+
+