From 2017d9a605d66b833e947b4c141c70cdf4c69250 Mon Sep 17 00:00:00 2001
From: Chris Hodapp <hodapp87@gmail.com>
Date: Tue, 6 Oct 2020 10:12:19 -0400
Subject: [PATCH] barbs example: end recursion by scale check, not iteration
 count

---
 src/examples.rs | 10 ++++++++--
 src/xform.rs    |  7 +++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/examples.rs b/src/examples.rs
index 7a3a3c0..633b8db 100644
--- a/src/examples.rs
+++ b/src/examples.rs
@@ -97,9 +97,15 @@ impl BarbsCtxt {
         }
     }
 
+    pub fn depth_check(&self, xform: &Transform, iters: usize) -> bool {
+        // Assume all scales are the same (for now)
+        let (s, _, _) = xform.get_scale();
+        return s < 0.005;
+    }
+
     pub fn barb(&mut self, iters: usize, xform: Transform, bound: [usize; 4]) {
 
-        if iters <= 0 {
+        if self.depth_check(&xform, iters) {
             self.faces.extend_from_slice(&[
                 bound[0], bound[2], bound[1],
                 bound[0], bound[3], bound[2],
@@ -118,7 +124,7 @@ impl BarbsCtxt {
 
     pub fn main(&mut self, iters: usize, xform: Transform, bound: [usize; 4]) {
 
-        if iters <= 0 {
+        if self.depth_check(&xform, iters) {
             self.faces.extend_from_slice(&[
                 bound[0], bound[2], bound[1],
                 bound[0], bound[3], bound[2],
diff --git a/src/xform.rs b/src/xform.rs
index 9f5e582..e529fa0 100644
--- a/src/xform.rs
+++ b/src/xform.rs
@@ -48,6 +48,13 @@ impl Transform {
     pub fn transform(&self, verts: &Vec<Vertex>) -> Vec<Vertex> {
         verts.iter().map(|v| self.mtx * v).collect()
     }
+
+    /// Returns X, Y, and Z scale factors for this transformation.
+    pub fn get_scale(&self) -> (f32, f32, f32) {
+        (self.mtx.column(0).norm(),
+         self.mtx.column(1).norm(),
+         self.mtx.column(2).norm())
+    }
 }
 
 impl Mul for Transform {