Merge pull request #978 from aftersomemath:depth-precision-in-place

PiperOrigin-RevId: 572961667
Change-Id: I69011ddf835ae286e30e7f84cca67867cfe94fa4

doc/APIreference/APItypes.rst

@@ -502,6 +502,16 @@ These are the possible framebuffers. They are used as an argument to the functio
 .. mujoco-include:: mjtFramebuffer
 
 
+mjtDepthMap
+~~~~~~~~~~~
+
+These are the depth mapping options. They are used as a value for the ``readPixelDepth`` attribute of the
+:ref:`mjrContext` struct, to control how the depth returned by :ref:`mjr_readPixels` is mapped from
+``znear`` to ``zfar``.
+
+.. mujoco-include:: mjtDepthMap
+
+
 .. _mjtFontScale:
 
 mjtFontScale

doc/changelog.rst

@@ -131,15 +131,19 @@ General
 22. Added multi-threaded constraint solving via :ref:`mj_island` and :ref:`mjThreadPool` to :ref:`testspeed<saTestspeed>`
     exposed via npoolthread flag. The `22 humanoids <https://github.com/deepmind/mujoco/blob/main/model/humanoid/22_humanoids.xml>`__
     model shows a 3x speedup compared to the single threaded simulation.
+23. Implemented reversed Z rendering for better depth precision. An enum :ref:`mjtDepthMap` was added with values
+    :ref:`mjDEPTH_ZERONEAR` and :ref:`mjDEPTH_ZEROFAR`, which can be used to set the new ``readDepthMap`` attribute in
+    :ref:`mjrContext`` to control how the depth returned by :ref:`mjr_readPixels` is mapped from ``znear`` to ``zfar``.
+    `Contribution <https://github.com/google-deepmind/mujoco/pull/978>`__ by `Levi Burner <https://github.com/aftersomemath>`__.
 
 Python bindings
 ^^^^^^^^^^^^^^^
 
-23. Fixed `#870 <https://github.com/google-deepmind/mujoco/issues/870>`__ where calling ``update_scene`` with an invalid
+24. Fixed `#870 <https://github.com/google-deepmind/mujoco/issues/870>`__ where calling ``update_scene`` with an invalid
     camera name used the default camera.
-24. Added ``user_scn`` to the :ref:`passive viewer<PyViewerPassive>` handle, which allows users to add custom
+25. Added ``user_scn`` to the :ref:`passive viewer<PyViewerPassive>` handle, which allows users to add custom
-    visualization geoms (`#1023 <https://github.com/google-deepmind/mujoco/issues/870>`__).
+   visualization geoms (`#1023 <https://github.com/google-deepmind/mujoco/issues/870>`__).
-25. Added optional boolean keyword arguments ``show_left_ui`` and ``show_right_ui`` to the functions ``viewer.launch``
+26. Added optional boolean keyword arguments ``show_left_ui`` and ``show_right_ui`` to the functions ``viewer.launch``
     and ``viewer.launch_passive``, which allow users to launch a viewer with UI panels hidden.
 
 Simulate
@@ -149,21 +153,21 @@ Simulate
    :align: right
    :width: 240px
 
-26. Added **state history** mechanism to :ref:`simulate<saSimulate>` and the managed
+27. Added **state history** mechanism to :ref:`simulate<saSimulate>` and the managed
     :ref:`Python viewer<PyViewerManaged>`. State history can be viewed by scrubbing the History slider and (more
     precisely) with the left and right arrow keys. See screen capture:
 
-27. The ``LOADING...`` label is now shown correctly.
+28. The ``LOADING...`` label is now shown correctly.
     `Contribution <https://github.com/google-deepmind/mujoco/pull/1070>`__ by
     `Levi Burner <https://github.com/aftersomemath>`__.
 
 Bug fixes
 ^^^^^^^^^
 
-28. Fixed a bug that was causing :ref:`geom margin<body-geom-margin>` to be ignored during the construction of
+29. Fixed a bug that was causing :ref:`geom margin<body-geom-margin>` to be ignored during the construction of
     midphase collision trees.
 
-29. Fixed a bug that was generating incorrect values in ``efc_diagApprox`` for weld equality constraints.
+30. Fixed a bug that was generating incorrect values in ``efc_diagApprox`` for weld equality constraints.
 
 
 Version 2.3.7 (July 20, 2023)

doc/includes/references.h

@@ -1443,6 +1443,10 @@ typedef enum mjtFramebuffer_ {    // OpenGL framebuffer option
   mjFB_WINDOW         = 0,        // default/window buffer
   mjFB_OFFSCREEN                  // offscreen buffer
 } mjtFramebuffer;
+typedef enum mjtDepthMap_ {       // depth mapping for `mjr_readPixels`
+  mjDEPTH_ZERONEAR    = 0,        // standard depth map; 0: znear, 1: zfar
+  mjDEPTH_ZEROFAR     = 1         // reversed depth map; 1: znear, 0: zfar
+} mjtDepthMap;
 typedef enum mjtFontScale_ {      // font scale, used at context creation
   mjFONTSCALE_50      = 50,       // 50% scale, suitable for low-res rendering
   mjFONTSCALE_100     = 100,      // normal scale, suitable in the absence of DPI scaling
@@ -1546,6 +1550,9 @@ struct mjrContext_ {              // custom OpenGL context
 
   // pixel output format
   int     readPixelFormat;        // default color pixel format for mjr_readPixels
+
+  // depth output format
+  int     readDepthMap;           // depth mapping: mjDEPTH_ZERONEAR or mjDEPTH_ZEROFAR
 };
 typedef struct mjrContext_ mjrContext;
 typedef enum mjtTaskStatus_ {  // status values for mjTask

include/mujoco/mjrender.h

@@ -43,6 +43,10 @@ typedef enum mjtFramebuffer_ {    // OpenGL framebuffer option
   mjFB_OFFSCREEN                  // offscreen buffer
 } mjtFramebuffer;
 
+typedef enum mjtDepthMap_ {       // depth mapping for `mjr_readPixels`
+  mjDEPTH_ZERONEAR    = 0,        // standard depth map; 0: znear, 1: zfar
+  mjDEPTH_ZEROFAR     = 1         // reversed depth map; 1: znear, 0: zfar
+} mjtDepthMap;
 
 typedef enum mjtFontScale_ {      // font scale, used at context creation
   mjFONTSCALE_50      = 50,       // 50% scale, suitable for low-res rendering
@@ -155,6 +159,9 @@ struct mjrContext_ {              // custom OpenGL context
 
   // pixel output format
   int     readPixelFormat;        // default color pixel format for mjr_readPixels
+
+  // depth output format
+  int     readDepthMap;           // depth mapping: mjDEPTH_ZERONEAR or mjDEPTH_ZEROFAR
 };
 typedef struct mjrContext_ mjrContext;
 

introspect/enums.py

@@ -650,6 +650,15 @@ ENUMS: Mapping[str, EnumDecl] = dict([
              ('mjFB_OFFSCREEN', 1),
          ]),
      )),
+    ('mjtDepthMap',
+     EnumDecl(
+         name='mjtDepthMap',
+         declname='enum mjtDepthMap_',
+         values=dict([
+             ('mjDEPTH_ZERONEAR', 0),
+             ('mjDEPTH_ZEROFAR', 1),
+         ]),
+     )),
     ('mjtFontScale',
      EnumDecl(
          name='mjtFontScale',

introspect/structs.py

@@ -7905,6 +7905,11 @@ STRUCTS: Mapping[str, StructDecl] = dict([
                  type=ValueType(name='int'),
                  doc='default color pixel format for mjr_readPixels',
              ),
+             StructFieldDecl(
+                 name='readDepthMap',
+                 type=ValueType(name='int'),
+                 doc='depth mapping: mjDEPTH_ZERONEAR or mjDEPTH_ZEROFAR',
+             ),
          ),
      )),
     ('mjuiState',

python/mujoco/render.cc

@@ -215,6 +215,7 @@ PYBIND11_MODULE(_render, pymodule) {
   X(windowDoublebuffer);
   X(currentBuffer);
   X(readPixelFormat);
+  X(readDepthMap);
 #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.readDepthMap = _enums.mjtDepthMap.mjDEPTH_ZEROFAR
 
     # Default render flags.
     self._depth_rendering = False
@@ -138,7 +139,9 @@ the clause:
     """
     original_flags = self._scene.flags.copy()
 
-    if self._segmentation_rendering:
+    # Using segmented rendering for depth makes the calculated depth more
+    # accurate at far distances.
+    if self._depth_rendering or self._segmentation_rendering:
       self._scene.flags[_enums.mjtRndFlag.mjRND_SEGMENT] = True
       self._scene.flags[_enums.mjtRndFlag.mjRND_IDCOLOR] = True
 
@@ -173,11 +176,34 @@ the clause:
       near = self._model.vis.map.znear * extent
       far = self._model.vis.map.zfar * extent
 
-      # Convert from [0 1] to depth in units of length, see links below:
+      # Calculate OpenGL perspective matrix values in float32 precision
-      # http://stackoverflow.com/a/6657284/1461210
+      # so they are close to what glFrustum returns
-      # https://www.khronos.org/opengl/wiki/Depth_Buffer_Precision
+      # https://registry.khronos.org/OpenGL-Refpages/gl2.1/xhtml/glFrustum.xml
-      out = near / (1 - out * (1 - near / far))
+      zfar = np.float32(far)
+      znear = np.float32(near)
+      c_coef = -(zfar + znear) / (zfar - znear)
+      d_coef = -(np.float32(2) * zfar * znear) / (zfar - znear)
 
+      # In reverse Z mode the perspective matrix is transformed by the following
+      c_coef = np.float32(-0.5) * c_coef - np.float32(0.5)
+      d_coef = np.float32(-0.5) * d_coef
+
+      # We need 64 bits to convert Z from ndc to metric depth without noticeable
+      # losses in precision
+      out_64 = out.astype(np.float64)
+
+      # Undo OpenGL projection
+      # Note: We do not need to take action to convert from window coordinates
+      # to normalized device coordinates because in reversed Z mode the mapping
+      # is identity
+      out_64 = d_coef / (out_64 + c_coef)
+
+      # Cast result back to float32 for backwards compatibility
+      # This has a small accuracy cost
+      out[:] = out_64.astype(np.float32)
+
+      # Reset scene flags.
+      np.copyto(self._scene.flags, original_flags)
     elif self._segmentation_rendering:
       _render.mjr_readPixels(out, None, self._rect, self._mjr_context)
 

src/render/glad/glad.c

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-// Based on the OpenGL loader generated by glad 0.1.35 on Mon Mar 21 12:42:33 2022.
+// Based on the OpenGL loader generated by glad 0.1.34 on Thu Jun 22 14:40:03 2023.
 //
 // The original generated code is distributed under CC0.
 // https://creativecommons.org/publicdomain/zero/1.0/
@@ -22,6 +22,8 @@
 // APIs: gl=1.5
 // Profile: compatibility
 // Extensions:
+//     GL_ARB_clip_control,
+//     GL_ARB_depth_buffer_float,
 //     GL_ARB_framebuffer_object,
 //     GL_ARB_seamless_cube_map,
 //     GL_ARB_vertex_buffer_object,
@@ -32,9 +34,9 @@
 // Reproducible: False
 //
 // Commandline:
-//     --profile="compatibility" --api="gl=1.5" --generator="c" --spec="gl" --extensions="GL_ARB_framebuffer_object,GL_ARB_seamless_cube_map,GL_ARB_vertex_buffer_object,GL_KHR_debug"
+//     --profile="compatibility" --api="gl=1.5" --generator="c" --spec="gl" --extensions="GL_ARB_clip_control,GL_ARB_depth_buffer_float,GL_ARB_framebuffer_object,GL_ARB_seamless_cube_map,GL_ARB_vertex_buffer_object,GL_KHR_debug"
 // Online:
-//     https://glad.dav1d.de/#profile=compatibility&language=c&specification=gl&loader=on&api=gl%3D1.5&extensions=GL_ARB_framebuffer_object&extensions=GL_ARB_seamless_cube_map&extensions=GL_ARB_vertex_buffer_object&extensions=GL_KHR_debug
+//     https://glad.dav1d.de/#profile=compatibility&language=c&specification=gl&loader=on&api=gl%3D1.5&extensions=GL_ARB_clip_control&extensions=GL_ARB_depth_buffer_float&extensions=GL_ARB_framebuffer_object&extensions=GL_ARB_seamless_cube_map&extensions=GL_ARB_vertex_buffer_object&extensions=GL_KHR_debug
 
 #if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC diagnostic push
@@ -829,10 +831,13 @@ PFNGLWINDOWPOS3IPROC mjGlad_glWindowPos3i = NULL;
 PFNGLWINDOWPOS3IVPROC mjGlad_glWindowPos3iv = NULL;
 PFNGLWINDOWPOS3SPROC mjGlad_glWindowPos3s = NULL;
 PFNGLWINDOWPOS3SVPROC mjGlad_glWindowPos3sv = NULL;
+int mjGLAD_GL_ARB_clip_control = 0;
+int mjGLAD_GL_ARB_depth_buffer_float = 0;
 int mjGLAD_GL_ARB_framebuffer_object = 0;
 int mjGLAD_GL_ARB_seamless_cube_map = 0;
 int mjGLAD_GL_ARB_vertex_buffer_object = 0;
 int mjGLAD_GL_KHR_debug = 0;
+PFNGLCLIPCONTROLPROC mjGlad_glClipControl = NULL;
 PFNGLISRENDERBUFFERPROC mjGlad_glIsRenderbuffer = NULL;
 PFNGLBINDRENDERBUFFERPROC mjGlad_glBindRenderbuffer = NULL;
 PFNGLDELETERENDERBUFFERSPROC mjGlad_glDeleteRenderbuffers = NULL;
@@ -1355,6 +1360,10 @@ static void mjGlad_load_GL_VERSION_1_5(GLADloadproc load) {
   mjGlad_glGetBufferParameteriv = (PFNGLGETBUFFERPARAMETERIVPROC)load("glGetBufferParameteriv");
   mjGlad_glGetBufferPointerv = (PFNGLGETBUFFERPOINTERVPROC)load("glGetBufferPointerv");
 }
+static void mjGlad_load_GL_ARB_clip_control(GLADloadproc load) {
+  if(!mjGLAD_GL_ARB_clip_control) return;
+  mjGlad_glClipControl = (PFNGLCLIPCONTROLPROC)load("glClipControl");
+}
 static void mjGlad_load_GL_ARB_framebuffer_object(GLADloadproc load) {
   if(!mjGLAD_GL_ARB_framebuffer_object) return;
   mjGlad_glIsRenderbuffer = (PFNGLISRENDERBUFFERPROC)load("glIsRenderbuffer");
@@ -1419,6 +1428,8 @@ static void mjGlad_load_GL_KHR_debug(GLADloadproc load) {
 }
 static int mjGlad_find_extensionsGL(void) {
   if (!mjGlad_get_exts()) return 0;
+  mjGLAD_GL_ARB_clip_control = mjGlad_has_ext("GL_ARB_clip_control");
+  mjGLAD_GL_ARB_depth_buffer_float = mjGlad_has_ext("GL_ARB_depth_buffer_float");
   mjGLAD_GL_ARB_framebuffer_object = mjGlad_has_ext("GL_ARB_framebuffer_object");
   mjGLAD_GL_ARB_seamless_cube_map = mjGlad_has_ext("GL_ARB_seamless_cube_map");
   mjGLAD_GL_ARB_vertex_buffer_object = mjGlad_has_ext("GL_ARB_vertex_buffer_object");
@@ -1491,6 +1502,7 @@ int mjGladLoadGLUnsafe(void) {
     mjGlad_load_GL_VERSION_1_5(mjGlad_get_proc);
 
     if (!mjGlad_find_extensionsGL()) return 0;
+    mjGlad_load_GL_ARB_clip_control(mjGlad_get_proc);
     mjGlad_load_GL_ARB_framebuffer_object(mjGlad_get_proc);
     mjGlad_load_GL_ARB_vertex_buffer_object(mjGlad_get_proc);
     mjGlad_load_GL_KHR_debug(mjGlad_get_proc);

src/render/glad/glad.h

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-// Based on the OpenGL loader generated by glad 0.1.35 on Mon Mar 21 12:42:33 2022.
+// Based on the OpenGL loader generated by glad 0.1.34 on Thu Jun 22 14:40:03 2023.
 //
 // The original generated code is distributed under CC0.
 // https://creativecommons.org/publicdomain/zero/1.0/
@@ -22,6 +22,8 @@
 // APIs: gl=1.5
 // Profile: compatibility
 // Extensions:
+//     GL_ARB_clip_control,
+//     GL_ARB_depth_buffer_float,
 //     GL_ARB_framebuffer_object,
 //     GL_ARB_seamless_cube_map,
 //     GL_ARB_vertex_buffer_object,
@@ -32,9 +34,9 @@
 // Reproducible: False
 //
 // Commandline:
-//     --profile="compatibility" --api="gl=1.5" --generator="c" --spec="gl" --extensions="GL_ARB_framebuffer_object,GL_ARB_seamless_cube_map,GL_ARB_vertex_buffer_object,GL_KHR_debug"
+//     --profile="compatibility" --api="gl=1.5" --generator="c" --spec="gl" --extensions="GL_ARB_clip_control,GL_ARB_depth_buffer_float,GL_ARB_framebuffer_object,GL_ARB_seamless_cube_map,GL_ARB_vertex_buffer_object,GL_KHR_debug"
 // Online:
-//     https://glad.dav1d.de/#profile=compatibility&language=c&specification=gl&loader=on&api=gl%3D1.5&extensions=GL_ARB_framebuffer_object&extensions=GL_ARB_seamless_cube_map&extensions=GL_ARB_vertex_buffer_object&extensions=GL_KHR_debug
+//     https://glad.dav1d.de/#profile=compatibility&language=c&specification=gl&loader=on&api=gl%3D1.5&extensions=GL_ARB_clip_control&extensions=GL_ARB_depth_buffer_float&extensions=GL_ARB_framebuffer_object&extensions=GL_ARB_seamless_cube_map&extensions=GL_ARB_vertex_buffer_object&extensions=GL_KHR_debug
 
 #ifndef MUJOCO_SRC_RENDER_GLAD_GLAD_H_
 #define MUJOCO_SRC_RENDER_GLAD_GLAD_H_
@@ -2304,6 +2306,15 @@ typedef void (APIENTRYP PFNGLGETBUFFERPOINTERVPROC)(GLenum target, GLenum pname,
 GLAPI PFNGLGETBUFFERPOINTERVPROC mjGlad_glGetBufferPointerv;
 #define glGetBufferPointerv mjGlad_glGetBufferPointerv
 #endif
+#define GL_LOWER_LEFT 0x8CA1
+#define GL_UPPER_LEFT 0x8CA2
+#define GL_NEGATIVE_ONE_TO_ONE 0x935E
+#define GL_ZERO_TO_ONE 0x935F
+#define GL_CLIP_ORIGIN 0x935C
+#define GL_CLIP_DEPTH_MODE 0x935D
+#define GL_DEPTH_COMPONENT32F 0x8CAC
+#define GL_DEPTH32F_STENCIL8 0x8CAD
+#define GL_FLOAT_32_UNSIGNED_INT_24_8_REV 0x8DAD
 #define GL_INVALID_FRAMEBUFFER_OPERATION 0x0506
 #define GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING 0x8210
 #define GL_FRAMEBUFFER_ATTACHMENT_COMPONENT_TYPE 0x8211
@@ -2487,6 +2498,17 @@ GLAPI PFNGLGETBUFFERPOINTERVPROC mjGlad_glGetBufferPointerv;
 #define GL_STACK_OVERFLOW_KHR 0x0503
 #define GL_STACK_UNDERFLOW_KHR 0x0504
 #define GL_DISPLAY_LIST 0x82E7
+#ifndef GL_ARB_clip_control
+#define GL_ARB_clip_control 1
+GLAPI int mjGLAD_GL_ARB_clip_control;
+typedef void (APIENTRYP PFNGLCLIPCONTROLPROC)(GLenum origin, GLenum depth);
+GLAPI PFNGLCLIPCONTROLPROC mjGlad_glClipControl;
+#define glClipControl mjGlad_glClipControl
+#endif
+#ifndef GL_ARB_depth_buffer_float
+#define GL_ARB_depth_buffer_float 1
+GLAPI int mjGLAD_GL_ARB_depth_buffer_float;
+#endif
 #ifndef GL_ARB_framebuffer_object
 #define GL_ARB_framebuffer_object 1
 GLAPI int mjGLAD_GL_ARB_framebuffer_object;

src/render/render_context.c

@@ -1062,7 +1062,7 @@ static void makeShadow(const mjModel* m, mjrContext* con) {
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);
-  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
+  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FUNC, GL_GEQUAL);
   glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_TEXTURE_MODE, GL_INTENSITY);
   glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
@@ -1126,11 +1126,14 @@ static void makeOff(mjrContext* con) {
     mju_error("Could not allocate offscreen depth and stencil buffer");
   }
   glBindRenderbuffer(GL_RENDERBUFFER, con->offDepthStencil);
+
+  GLenum depth_buffer_format =
+      mjGLAD_GL_ARB_depth_buffer_float ? GL_DEPTH32F_STENCIL8 : GL_DEPTH24_STENCIL8;
   if (con->offSamples) {
-    glRenderbufferStorageMultisample(GL_RENDERBUFFER, con->offSamples, GL_DEPTH24_STENCIL8,
+    glRenderbufferStorageMultisample(GL_RENDERBUFFER, con->offSamples, depth_buffer_format,
                                      con->offWidth, con->offHeight);
   } else {
-    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, con->offWidth, con->offHeight);
+    glRenderbufferStorage(GL_RENDERBUFFER, depth_buffer_format, con->offWidth, con->offHeight);
   }
   glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT,
                             GL_RENDERBUFFER, con->offDepthStencil);
@@ -1169,7 +1172,7 @@ static void makeOff(mjrContext* con) {
       mju_error("Could not allocate offscreen depth and stencil buffer_r");
     }
     glBindRenderbuffer(GL_RENDERBUFFER, con->offDepthStencil_r);
-    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, con->offWidth, con->offHeight);
+    glRenderbufferStorage(GL_RENDERBUFFER, depth_buffer_format, con->offWidth, con->offHeight);
     glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT,
                               GL_RENDERBUFFER, con->offDepthStencil_r);
 
@@ -1535,7 +1538,6 @@ void mjr_makeContext_offSize(const mjModel* m, mjrContext* con, int fontscale,
   glPixelStorei(GL_PACK_ALIGNMENT, 1);
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 
-  // free previous context
   mjr_freeContext(con);
 
   // no model: offscreen and font only
@@ -1607,6 +1609,9 @@ 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->readDepthMap = mjDEPTH_ZERONEAR;
 }
 
 
@@ -1830,10 +1835,10 @@ MJAPI void mjr_resizeOffscreen(int width, int height, mjrContext* con) {
 
   glBindRenderbuffer(GL_RENDERBUFFER, con->offDepthStencil);
   if (con->offSamples) {
-    glRenderbufferStorageMultisample(GL_RENDERBUFFER, con->offSamples, GL_DEPTH24_STENCIL8,
+    glRenderbufferStorageMultisample(GL_RENDERBUFFER, con->offSamples, GL_DEPTH32F_STENCIL8,
                                      con->offWidth, con->offHeight);
   } else {
-    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, con->offWidth, con->offHeight);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH32F_STENCIL8, con->offWidth, con->offHeight);
   }
 
   if (con->offSamples) {
@@ -1841,6 +1846,6 @@ MJAPI void mjr_resizeOffscreen(int width, int height, mjrContext* con) {
     glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8, con->offWidth, con->offHeight);
 
     glBindRenderbuffer(GL_RENDERBUFFER, con->offDepthStencil_r);
-    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, con->offWidth, con->offHeight);
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH32F_STENCIL8, con->offWidth, con->offHeight);
   }
 }

src/render/render_gl2.c

@@ -14,6 +14,7 @@
 
 #include "render/render_gl2.h"
 
+#include <math.h>
 #include <string.h>
 #include <stdio.h>
 
@@ -92,6 +93,23 @@ void mjr_restoreBuffer(const mjrContext* con) {
 
 
 
+static inline void flipDepthIfRequired(float* depth, mjrRect viewport, const mjrContext* con) {
+  if (con->readDepthMap == mjDEPTH_ZERONEAR) {
+    int npixel = viewport.width * viewport.height;
+    for (int i = 0; i < npixel; i++) {
+      depth[i] = 1.0 - depth[i];  // Reverse the reversed Z buffer
+    }
+  } else if (!mjGLAD_GL_ARB_clip_control) {
+    mju_warning("ARB_clip_control unavailable while mjDEPTH_ZEROFAR requested, "
+                "depth accuracy will be limited");
+  } else if (!mjGLAD_GL_ARB_depth_buffer_float) {
+    mju_warning("ARB_depth_buffer_float unavailable while mjDEPTH_ZEROFAR requested, "
+                "depth accuracy will be limited");
+  }
+}
+
+
+
 // read pixels from current OpenGL framebuffer to client buffer
 //  viewport is in OpenGL framebuffer; client buffer starts at (0,0)
 void mjr_readPixels(unsigned char* rgb, float* depth,
@@ -115,6 +133,7 @@ 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);
+      flipDepthIfRequired(depth, viewport, con);
     }
   }
 
@@ -159,6 +178,7 @@ 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);
+      flipDepthIfRequired(depth, viewport, con);
     }
 
     // restore currentBuffer
@@ -432,7 +452,6 @@ void mjr_text(int font, const char* txt, const mjrContext* con,
 static int draw_overlay(int font, mjrRect viewport, int skip, int gridpos,
                         float red, float green, float blue,
                         const char* overlay, const mjrContext* con) {
-
   int pos, ncthis, nc, nr, W, H, flg_big = (font == mjFONT_BIG);
   int PAD = 5, sz = mjMIN(mjMAXOVERLAY, (int)strlen(overlay));
   char text[mjMAXOVERLAY];

src/render/render_gl3.c

@@ -580,6 +580,9 @@ static void initGL3(const mjvScene* scn, const mjrContext* con) {
   // common options
   glDisable(GL_BLEND);
   glEnable(GL_NORMALIZE);
+  if (mjGLAD_GL_ARB_clip_control) {
+    glClipControl(GL_LOWER_LEFT, GL_ZERO_TO_ONE);
+  }
   glEnable(GL_DEPTH_TEST);
   glDepthMask(GL_TRUE);
   if (scn->flags[mjRND_CULL_FACE]) {
@@ -588,11 +591,11 @@ static void initGL3(const mjvScene* scn, const mjrContext* con) {
     glDisable(GL_CULL_FACE);
   }
   glShadeModel(GL_SMOOTH);
-  glDepthFunc(GL_LEQUAL);
+  glDepthFunc(GL_GEQUAL);
   glDepthRange(0, 1);
   glAlphaFunc(GL_GEQUAL, 0.99f);
   glClearColor(0, 0, 0, 0);
-  glClearDepth(1);
+  glClearDepth(0);
   glClearStencil(0);
   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
 
@@ -682,6 +685,15 @@ static void setView(int view, mjrRect viewport, const mjvScene* scn, const mjrCo
   // set projection
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
+  if (mjGLAD_GL_ARB_clip_control) {
+    // reverse Z rendering mapping [znear, zfar] -> [1, 0] (ndc)
+    glTranslatef(0.0f, 0.0f, 0.5f);
+    glScalef(1.0f, 1.0f, -0.5f);
+  }
+  else {
+    // reverse Z rendering mapping without shift [znear, zfar] -> [1, -1] (ndc)
+    glScalef(1.0f, 1.0f, -1.0f);
+  }
   glFrustum(cam.frustum_center - halfwidth,
             cam.frustum_center + halfwidth,
             cam.frustum_bottom,
@@ -757,9 +769,15 @@ void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
   float biasMatrix[16] = {
     0.5f, 0.0f, 0.0f, 0.0f,
     0.0f, 0.5f, 0.0f, 0.0f,
-    0.0f, 0.0f, 0.5f, 0.0f,
+    0.0f, 0.0f, 1.0f, 0.0f,
-    0.5f, 0.5f, 0.5f, 1.0f
+    0.5f, 0.5f, 0.0f, 1.0f
   };
+  if (!mjGLAD_GL_ARB_clip_control) {
+    // account for conversion from ndc to window coordinates
+    biasMatrix[2*4+2] = 0.5;
+    biasMatrix[3*4+2] = 0.5;
+  }
+
   float tempMatrix[16], textureMatrix[16];
   mjvGeom *thisgeom, tempgeom;
   mjvLight *thislight;
@@ -884,7 +902,7 @@ void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
   }
 
   // render with stereo
-  for (int view=(stereo?0:-1); view < (stereo?2:0); view++) {
+  for (int view = (stereo ? 0 : -1); view < (stereo ? 2 : 0); view++) {
     // change drawbuffer for QUADBUFFERED stereo
     if (stereo == mjSTEREO_QUADBUFFERED) {
       if (con->windowDoublebuffer) {
@@ -1107,6 +1125,15 @@ void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
           // set projection: from light viewpoint
           glMatrixMode(GL_PROJECTION);
           glLoadIdentity();
+          if (mjGLAD_GL_ARB_clip_control) {
+            // reverse Z rendering mapping [znear, zfar] -> [1, 0] (ndc)
+            glTranslatef(0.0f, 0.0f, 0.5f);
+            glScalef(1.0f, 1.0f, -0.5f);
+          }
+          else {
+            // reverse Z rendering mapping without shift [znear, zfar] -> [1, -1] (ndc)
+            glScalef(1.0f, 1.0f, -1.0f);
+          }
           if (thislight->directional) {
             glOrtho(-con->shadowClip, con->shadowClip,
                     -con->shadowClip, con->shadowClip,
@@ -1127,7 +1154,8 @@ void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
           glBindFramebuffer(GL_FRAMEBUFFER, con->shadowFBO);
           glDrawBuffer(GL_NONE);
           glClear(GL_DEPTH_BUFFER_BIT);
-          glViewport(1, 1, con->shadowSize-2, con->shadowSize-2); // avoid infinite shadows from edges
+          glViewport(
+              1, 1, con->shadowSize-2, con->shadowSize-2);  // avoid infinite shadows from edges
           glCullFace(GL_FRONT);
           glShadeModel(GL_FLAT);
           glDisable(GL_LIGHTING);

unity/Runtime/Bindings/MjBindings.cs

@@ -406,6 +406,10 @@ public enum mjtFramebuffer : int{
   mjFB_WINDOW = 0,
   mjFB_OFFSCREEN = 1,
 }
+public enum mjtDepthMap : int{
+  mjDEPTH_ZERONEAR = 0,
+  mjDEPTH_ZEROFAR = 1,
+}
 public enum mjtFontScale : int{
   mjFONTSCALE_50 = 50,
   mjFONTSCALE_100 = 100,
@@ -5596,6 +5600,7 @@ public unsafe struct mjrContext_ {
   public int windowDoublebuffer;
   public int currentBuffer;
   public int readPixelFormat;
+  public int readDepthMap;
 }
 
 [StructLayout(LayoutKind.Sequential)]