Add flag to mjrContext to support legacy depth mapping by default

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