From 581f009c02258f243915c45a5b736703944f935f Mon Sep 17 00:00:00 2001
From: Levi Burner <leviburner@gmail.com>
Date: Thu, 4 Aug 2022 19:16:50 -0400
Subject: [PATCH] Cull face flag

---
 doc/APIreference.rst                     | 1 +
 include/mujoco/mjvisualize.h             | 1 +
 introspect/enums.py                      | 3 ++-
 simulate/simulate.cc                     | 4 +++-
 src/engine/engine_vis_init.c             | 3 ++-
 src/render/render_gl3.c                  | 6 +++++-
 unity/Runtime/Bindings/MujocoBindings.cs | 3 ++-
 7 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/doc/APIreference.rst b/doc/APIreference.rst
index d1d69629..0f84d287 100644
--- a/doc/APIreference.rst
+++ b/doc/APIreference.rst
@@ -874,6 +874,7 @@ mjtRndFlag
        mjRND_HAZE,                     // haze
        mjRND_SEGMENT,                  // segmentation with random color
        mjRND_IDCOLOR,                  // segmentation with segid color
+       mjRND_CULL_FACE,                // cull backward faces
 
        mjNRNDFLAG                      // number of rendering flags
    } mjtRndFlag;
diff --git a/include/mujoco/mjvisualize.h b/include/mujoco/mjvisualize.h
index 4237165b..62ded42b 100644
--- a/include/mujoco/mjvisualize.h
+++ b/include/mujoco/mjvisualize.h
@@ -134,6 +134,7 @@ typedef enum mjtRndFlag_ {        // flags enabling rendering effects
   mjRND_HAZE,                     // haze
   mjRND_SEGMENT,                  // segmentation with random color
   mjRND_IDCOLOR,                  // segmentation with segid color
+  mjRND_CULL_FACE,                // cull backward faces
 
   mjNRNDFLAG                      // number of rendering flags
 } mjtRndFlag;
diff --git a/introspect/enums.py b/introspect/enums.py
index e9b27eb8..c319d69e 100755
--- a/introspect/enums.py
+++ b/introspect/enums.py
@@ -624,7 +624,8 @@ ENUMS: Mapping[str, EnumDecl] = dict([
              ('mjRND_HAZE', 6),
              ('mjRND_SEGMENT', 7),
              ('mjRND_IDCOLOR', 8),
-             ('mjNRNDFLAG', 9),
+             ('mjRND_CULL_FACE', 9),
+             ('mjNRNDFLAG', 10),
          ]),
      )),
     ('mjtStereo',
diff --git a/simulate/simulate.cc b/simulate/simulate.cc
index 32707ba2..152f0ef4 100644
--- a/simulate/simulate.cc
+++ b/simulate/simulate.cc
@@ -706,7 +706,9 @@ void makerendering(mj::Simulate* sim, int oldstate) {
   mjui_add(&sim->ui0, defOpenGL);
   for (i=0; i<mjNRNDFLAG; i++) {
     mju::strcpy_arr(defFlag[0].name, mjRNDSTRING[i][0]);
-    mju::sprintf_arr(defFlag[0].other, " %s", mjRNDSTRING[i][2]);
+    if (mjRNDSTRING[i][2][0]) {
+      mju::sprintf_arr(defFlag[0].other, " %s", mjRNDSTRING[i][2]);
+    }
     defFlag[0].pdata = sim->scn.flags + i;
     mjui_add(&sim->ui0, defFlag);
   }
diff --git a/src/engine/engine_vis_init.c b/src/engine/engine_vis_init.c
index 6f716cd2..341c9124 100644
--- a/src/engine/engine_vis_init.c
+++ b/src/engine/engine_vis_init.c
@@ -101,7 +101,8 @@ const char* mjRNDSTRING[mjNRNDFLAG][3] = {
   {"Fog",         "0", "G"},
   {"Haze",        "1", "/"},
   {"Segment",     "0", ","},
-  {"Id Color",    "0", "."}
+  {"Id Color",    "0", "."},
+  {"Cull Face",   "1", ""}
 };
 
 
diff --git a/src/render/render_gl3.c b/src/render/render_gl3.c
index b3c5f341..a51dbc06 100644
--- a/src/render/render_gl3.c
+++ b/src/render/render_gl3.c
@@ -491,7 +491,11 @@ static void initGL3(const mjvScene* scn, const mjrContext* con) {
   glEnable(GL_NORMALIZE);
   glEnable(GL_DEPTH_TEST);
   glDepthMask(GL_TRUE);
-  glEnable(GL_CULL_FACE);
+  if (scn->flags[mjRND_CULL_FACE]) {
+    glEnable(GL_CULL_FACE);
+  } else {
+    glDisable(GL_CULL_FACE);
+  }
   glShadeModel(GL_SMOOTH);
   glDepthFunc(GL_LEQUAL);
   glDepthRange(0, 1);
diff --git a/unity/Runtime/Bindings/MujocoBindings.cs b/unity/Runtime/Bindings/MujocoBindings.cs
index 0e33dd4d..c395aa33 100644
--- a/unity/Runtime/Bindings/MujocoBindings.cs
+++ b/unity/Runtime/Bindings/MujocoBindings.cs
@@ -480,7 +480,8 @@ public enum mjtRndFlag : int{
   mjRND_HAZE = 6,
   mjRND_SEGMENT = 7,
   mjRND_IDCOLOR = 8,
-  mjNRNDFLAG = 9,
+  mjRND_CULL_FACE = 9,
+  mjNRNDFLAG = 10,
 }
 public enum mjtStereo : int{
   mjSTEREO_NONE = 0,