Fix flex textures for 3D grids.

Fixes #2013.

PiperOrigin-RevId: 728673726
Change-Id: Idb2b6bf9e5392576d0b09f3e71dbea6f4636ae81

doc/includes/references.h

@@ -3011,6 +3011,7 @@ struct mjvSceneState_ {
     mjtNum* flex_node;
     mjtNum* flex_radius;
     float* flex_rgba;
+    float* flex_texcoord;
 
     int* hfield_pathadr;
 

include/mujoco/mjvisualize.h

@@ -537,6 +537,7 @@ struct mjvSceneState_ {
     mjtNum* flex_node;
     mjtNum* flex_radius;
     float* flex_rgba;
+    float* flex_texcoord;
 
     int* hfield_pathadr;
 

include/mujoco/mjxmacro.h

@@ -373,7 +373,7 @@
     XMJV( int,     flex_bvhadr,           nflex,         1                    ) \
     XMJV( int,     flex_bvhnum,           nflex,         1                    ) \
     XMJV( float,   flex_rgba,             nflex,         4                    ) \
-    X   ( float,   flex_texcoord,         nflextexcoord, 2                    ) \
+    XMJV( float,   flex_texcoord,         nflextexcoord, 2                    ) \
     X   ( int,     mesh_vertadr,          nmesh,         1                    ) \
     X   ( int,     mesh_vertnum,          nmesh,         1                    ) \
     X   ( int,     mesh_normaladr,        nmesh,         1                    ) \

introspect/structs.py

@@ -7734,6 +7734,13 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                              ),
                              doc='',
                          ),
+                         StructFieldDecl(
+                             name='flex_texcoord',
+                             type=PointerType(
+                                 inner_type=ValueType(name='float'),
+                             ),
+                             doc='',
+                         ),
                          StructFieldDecl(
                              name='hfield_pathadr',
                              type=PointerType(

src/user/user_flexcomp.cc

@@ -597,7 +597,7 @@ int mjCFlexcomp::GridID(int ix, int iy, int iz) {
 // make grid
 bool mjCFlexcomp::MakeGrid(char* error, int error_sz) {
   int dim = def.Flex().spec.dim;
-  bool hastex = texcoord.empty();
+  bool needtex = texcoord.empty() && mjs_getString(def.spec.flex->material)[0];
 
   // 1D
   if (dim == 1) {
@@ -646,7 +646,7 @@ bool mjCFlexcomp::MakeGrid(char* error, int error_sz) {
         point.push_back(0);
 
         // add texture coordinates, if not specified explicitly
-        if (!hastex) {
+        if (needtex) {
           texcoord.push_back(ix/(double)std::max(count[0]-1, 1));
           texcoord.push_back(iy/(double)std::max(count[1]-1, 1));
         }
@@ -690,6 +690,12 @@ bool mjCFlexcomp::MakeGrid(char* error, int error_sz) {
           point.push_back(spacing[1]*(iy - 0.5*(count[1]-1)));
           point.push_back(spacing[2]*(iz - 0.5*(count[2]-1)));
 
+          // add texture coordinates, if not specified explicitly
+          if (needtex) {
+            texcoord.push_back(ix/(float)std::max(count[0]-1, 1));
+            texcoord.push_back(iy/(float)std::max(count[1]-1, 1));
+          }
+
           // add elements
           if (ix < count[0]-1 && iy < count[1]-1 && iz < count[2]-1) {
             int vert[8] = {
@@ -834,7 +840,7 @@ bool mjCFlexcomp::MakeSquare(char* error, int error_sz) {
 // make 3d box, ellipsoid or cylinder
 bool mjCFlexcomp::MakeBox(char* error, int error_sz) {
   double pos[3];
-  bool needtex = texcoord.empty() && !std::string(mjs_getString(def.spec.flex->material)).empty();
+  bool needtex = texcoord.empty() && mjs_getString(def.spec.flex->material)[0];
 
   // set 3D
   def.spec.flex->dim = 3;

unity/Runtime/Bindings/MjBindings.cs

@@ -6338,6 +6338,7 @@ public unsafe struct model {
   public double* flex_node;
   public double* flex_radius;
   public float* flex_rgba;
+  public float* flex_texcoord;
   public int* hfield_pathadr;
   public int* mesh_bvhadr;
   public int* mesh_bvhnum;