Add flag to mjrContext to support legacy depth mapping by default

include/mujoco/mjrender.h

@@ -39,6 +39,10 @@ typedef enum mjtFramebuffer_ {    // OpenGL framebuffer option
   mjFB_OFFSCREEN                  // offscreen buffer
 } mjtFramebuffer;
 
+typedef enum mjtDepthMapping_ {   // OpenGL depth buffer readout mapping (from znear to zfar)
+  mjDM_ZEROTOONE  = 0,            // Legacy default, reverses reversed Z rendering, performance penalty
+  mjDM_ONETOZERO                  // Native output of reversed Z rendering, decreases numerical error
+} mjtDepthMapping;
 
 typedef enum mjtFontScale_ {      // font scale, used at context creation
   mjFONTSCALE_50      = 50,       // 50% scale, suitable for low-res rendering
@@ -151,6 +155,9 @@ struct mjrContext_ {              // custom OpenGL context
 
   // pixel output format
   int     readPixelFormat;        // default color pixel format for mjr_readPixels
+
+  // depth output format
+  int     readDepthMapping;       // depth mapping, 0 to 1 (default, legacy), or 1 to 0 (reversed, native)
 };
 typedef struct mjrContext_ mjrContext;
 

introspect/enums.py

@@ -621,6 +621,15 @@ ENUMS: Mapping[str, EnumDecl] = dict([
              ('mjFB_OFFSCREEN', 1),
          ]),
      )),
+    ('mjtDepthMapping',
+     EnumDecl(
+         name='mjtDepthMapping',
+         declname='enum mjtDepthMapping_',
+         values=dict([
+             ('mjDM_ZEROTOONE', 0),
+             ('mjDM_ONETOZERO', 1),
+         ]),
+     )),
     ('mjtFontScale',
      EnumDecl(
          name='mjtFontScale',

introspect/structs.py

@@ -7126,6 +7126,11 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                  type=ValueType(name='int'),
                  doc='default color pixel format for mjr_readPixels',
              ),
+             StructFieldDecl(
+                 name='readDepthMapping',
+                 type=ValueType(name='int'),
+                 doc='depth mapping, 0 to 1 (default, legacy), or 1 to 0 (reversed, native)',  # pylint: disable=line-too-long
+             ),
          ),
      )),
     ('mjuiState',

python/mujoco/render.cc

@@ -215,6 +215,7 @@ PYBIND11_MODULE(_render, pymodule) {
   X(windowDoublebuffer);
   X(currentBuffer);
   X(readPixelFormat);
+  X(readDepthMapping);
 #undef X
 
 #define X(var)                      \

python/mujoco/renderer.py

@@ -86,6 +86,7 @@ the clause:
     _render.mjr_setBuffer(
         _enums.mjtFramebuffer.mjFB_OFFSCREEN.value, self._mjr_context
     )
+    self._mjr_context.readDepthMapping = _enums.mjtDepthMapping.mjDM_ONETOZERO
 
     # Default render flags.
     self._depth_rendering = False
@@ -196,6 +197,7 @@ the clause:
       out_64 = D / (out_64 + C)
 
       # Cast result back to float32 for backwards compatibility
+      # This has a small accuracy cost
       out[:] = out_64.astype(np.float32)
 
       # Reset scene flags.

src/render/render_context.c

@@ -1612,6 +1612,9 @@ void mjr_makeContext_offSize(const mjModel* m, mjrContext* con, int fontscale,
 
   // set default color pixel format for mjr_readPixels
   con->readPixelFormat = GL_RGB;
+
+  // set default depth mapping for mjr_readPixels
+  con->readDepthMapping = mjDM_ZEROTOONE;
 }
 
 

src/render/render_gl2.c

@@ -115,6 +115,10 @@ void mjr_readPixels(unsigned char* rgb, float* depth,
     if (depth) {
       glReadPixels(viewport.left, viewport.bottom, viewport.width, viewport.height,
                    GL_DEPTH_COMPONENT, GL_FLOAT, depth);
+      if (con->readDepthMapping == mjDM_ZEROTOONE) {
+        int N_pixels = viewport.width * viewport.height;
+        for (int i = 0; i < N_pixels; i++) depth[i] = 1.0 - depth[i]; // Reverse the reversed Z buffer
+      }
     }
   }
 
@@ -159,6 +163,11 @@ void mjr_readPixels(unsigned char* rgb, float* depth,
     if (depth) {
       glReadPixels(viewport.left, viewport.bottom, viewport.width, viewport.height,
                    GL_DEPTH_COMPONENT, GL_FLOAT, depth);
+
+      if (con->readDepthMapping == mjDM_ZEROTOONE) {
+        int N_pixels = viewport.width * viewport.height;
+        for (int i = 0; i < N_pixels; i++) depth[i] = 1.0 - depth[i]; // Reverse the reversed Z buffer
+      }
     }
 
     // restore currentBuffer

unity/Runtime/Bindings/MjBindings.cs

@@ -389,6 +389,10 @@ public enum mjtFramebuffer : int{
   mjFB_WINDOW = 0,
   mjFB_OFFSCREEN = 1,
 }
+public enum mjtDepthMapping : int{
+  mjDM_ZEROTOONE = 0,
+  mjDM_ONETOZERO = 1,
+}
 public enum mjtFontScale : int{
   mjFONTSCALE_50 = 50,
   mjFONTSCALE_100 = 100,