From 9a0f2c36013f13a212fcdb4149e86eea49558575 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Fri, 18 Nov 2016 11:00:55 +0000
Subject: [PATCH] Fix detection of transparent meshes.

SSurface::TriangulateInto first populates the mesh with triangles
that have no color, and then paints them, which confused the code
that detects if a mesh is transparent into thinking that all of them
are; and that broke the "draw back faces in red" feature, since it
is disabled for transparent meshes.
---
 CHANGELOG.md        | 1 +
 src/mesh.cpp        | 3 ++-
 src/srf/surface.cpp | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b315eb4..466ad25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -43,6 +43,7 @@ Other new features:
 Bug fixes:
   * Do not crash when applying a symmetry constraint to two points.
   * Fix TTF font metrics again (properly this time).
+  * Fix the "draw back faces in red" option.
   * Various minor crashes.
 
 2.2
diff --git a/src/mesh.cpp b/src/mesh.cpp
index fe84248..c909f8b 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -34,7 +34,8 @@ void SMesh::AddTriangle(STriMeta meta, Vector a, Vector b, Vector c) {
     AddTriangle(&t);
 }
 void SMesh::AddTriangle(const STriangle *st) {
-    if(st->meta.color.alpha != 255) isTransparent = true;
+    RgbaColor color = st->meta.color;
+    if(!color.IsEmpty() && color.alpha != 255) isTransparent = true;
     l.Add(st);
 }
 
diff --git a/src/srf/surface.cpp b/src/srf/surface.cpp
index 62e2088..1645c1c 100644
--- a/src/srf/surface.cpp
+++ b/src/srf/surface.cpp
@@ -424,6 +424,7 @@ void SSurface::TriangulateInto(SShell *shell, SMesh *sm) {
         for(i = start; i < sm->l.n; i++) {
             STriangle *st = &(sm->l.elem[i]);
             st->meta = meta;
+            if(st->meta.color.alpha != 255) sm->isTransparent = true;
             st->an = NormalAt(st->a.x, st->a.y);
             st->bn = NormalAt(st->b.x, st->b.y);
             st->cn = NormalAt(st->c.x, st->c.y);