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;