Simplify MuJoCo Studio viewer selection and unify model flags.

This change removes the ViewerMode enum and instead infers whether to launch the Web Viewer or Native Viewer based on the graphics mode (gfx) setting. Specifically, setting gfx to "web" or "webgl" will now launch the Web Viewer (in future "webgpu" would also launch the Web Viewer).

Additionally, this unifies command-line flags across studio scripts and samples by replacing the --mjcf flag with --model (with positional argument fallback) and standardizing absl flags usage. --model is a better name since formats like .mjz and .mjb are also supported by this argument.

PiperOrigin-RevId: 959058940
Change-Id: If4e0ace664ddc6e45cb681d168679148e8c4901d

python/mujoco/experimental/studio/sample/ghost.py

@@ -38,12 +38,15 @@ from mujoco.experimental.dear_imgui import dear_imgui as imgui
 
 vp = viewer_protocol
 
-_GFX = _flags.DEFINE_enum('gfx', None, vp.GFX_MODES, 'Graphics mode.')
+_MODEL = _flags.DEFINE_string('model', None, 'Path to model file.')
+_GFX = _flags.DEFINE_enum(
+    'gfx', None, vp.GFX_MODES, 'Graphics mode ("web" launches Web Viewer).'
+)
+_PORT = _flags.DEFINE_integer(
+    'port', 0, 'Web Viewer port (0 picks first free port >= 8080).'
+)
 _WIDTH = _flags.DEFINE_integer('width', 1200, 'Width of the output image.')
 _HEIGHT = _flags.DEFINE_integer('height', 800, 'Height of the output image')
-_VIEWER = _flags.DEFINE_enum_class(
-    'viewer', vp.ViewerMode.NATIVE, vp.ViewerMode, 'Viewer mode.'
-)
 
 
 class GhostRenderer:
@@ -155,15 +158,18 @@ class GhostRenderer:
 
 
 def main(argv: list[str]) -> None:
-  if len(argv) != 2:
-    raise _app.UsageError('Please provide exactly one MJCF path argument.')
+  model_path = _MODEL.value or (
+      argv[1] if len(argv) > 1 and not argv[1].startswith('--') else None
+  )
+  if not model_path:
+    raise _app.UsageError('Please provide a model path argument or --model flag.')
 
   data = None
   try:
-    if (data := parser.parse(argv[1])) is None:
+    if (data := parser.parse(model_path)) is None:
       raise ValueError('parser returned None')
   except Exception as ex:  # pylint: disable=broad-except
-    print(f'Failed to load model from {argv[1]!r}: {ex}')
+    print(f'Failed to load model from {model_path!r}: {ex}')
     sys.exit(1)
   model = data.model
 
@@ -172,7 +178,7 @@ def main(argv: list[str]) -> None:
       width=_WIDTH.value,
       height=_HEIGHT.value,
       gfx=_GFX.value or '',
-      viewer_mode=_VIEWER.value,
+      http_port=_PORT.value,
   )
 
   ghost_renderer = GhostRenderer()

python/mujoco/experimental/studio/sample/implot.py

@@ -17,7 +17,7 @@ This script runs a Studio viewer and adds an 'Inspect Body' window using ImGui
 and ImPlot bindings to visualize selected body data. The example demonstrates
 how responsive UI layout rules are easily implemented.
 
-Provide an MJCF model file via the first command-line argument to launch.
+Provide a model file via the --model flag or positional argument to launch.
 """
 
 import math
@@ -40,12 +40,15 @@ from mujoco.experimental.implot import implot
 
 vp = viewer_protocol
 
-_GFX = _flags.DEFINE_enum('gfx', None, vp.GFX_MODES, 'Graphics mode.')
+_MODEL = _flags.DEFINE_string('model', None, 'Path to model file.')
+_GFX = _flags.DEFINE_enum(
+    'gfx', None, vp.GFX_MODES, 'Graphics mode ("web" launches Web Viewer).'
+)
+_PORT = _flags.DEFINE_integer(
+    'port', 0, 'Web Viewer port (0 picks first free port >= 8080).'
+)
 _WIDTH = _flags.DEFINE_integer('width', 1200, 'Width of the output image.')
 _HEIGHT = _flags.DEFINE_integer('height', 800, 'Height of the output image')
-_VIEWER = _flags.DEFINE_enum_class(
-    'viewer', vp.ViewerMode.NATIVE, vp.ViewerMode, 'Viewer mode.'
-)
 
 
 _N_HISTORY = 100
@@ -211,12 +214,15 @@ class BodyInspector:
 
 
 def main(argv: list[str]) -> None:
-  if len(argv) < 2:
-    print('Usage: implot <model_path.xml>')
+  model_path = _MODEL.value or (
+      argv[1] if len(argv) > 1 and not argv[1].startswith('--') else None
+  )
+  if not model_path:
+    print('Usage: implot --model=<model_path.xml>')
     sys.exit(1)
 
-  if (data := parser.parse(argv[1])) is None:
-    print(f'Error loading model from {argv[1]!r}')
+  if (data := parser.parse(model_path)) is None:
+    print(f'Error loading model from {model_path!r}')
     sys.exit(1)
   model = data.model
 
@@ -227,7 +233,7 @@ def main(argv: list[str]) -> None:
       width=_WIDTH.value,
       height=_HEIGHT.value,
       gfx=_GFX.value or '',
-      viewer_mode=_VIEWER.value,
+      http_port=_PORT.value,
   )
 
   with launch_passive.launch_passive(

python/mujoco/experimental/studio/sample/render.py

@@ -16,37 +16,38 @@
 import os
 import sys
 
-from absl import app
-from absl import flags
+from absl import app as _app
+from absl import flags as _flags
 import mujoco
 from mujoco.experimental.studio import parser
 from mujoco.experimental.studio import renderer
 from mujoco.experimental.studio import viewer_protocol
 from PIL import Image
 
-_MODEL = flags.DEFINE_string('model', '', 'Model file to load.')
-_OUTPUT = flags.DEFINE_string('output', '', 'Output file to save.')
-_GFX = flags.DEFINE_enum(
+_MODEL = _flags.DEFINE_string('model', None, 'Path to model file.')
+_OUTPUT = _flags.DEFINE_string('output', '', 'Output file to save.')
+_GFX = _flags.DEFINE_enum(
     'gfx', None, viewer_protocol.GFX_MODES, 'Rendering graphics mode.'
 )
-_WIDTH = flags.DEFINE_integer('width', 320, 'Width of the output image.')
-_HEIGHT = flags.DEFINE_integer('height', 240, 'Height of the output image.')
-_STEPS = flags.DEFINE_integer('steps', 1, 'Number of steps before render.')
+_WIDTH = _flags.DEFINE_integer('width', 320, 'Width of the output image.')
+_HEIGHT = _flags.DEFINE_integer('height', 240, 'Height of the output image.')
+_STEPS = _flags.DEFINE_integer('steps', 1, 'Number of steps before render.')
 
 
-def main(argv):
-  if len(argv) > 1:
-    raise app.UsageError('Too many command-line arguments.')
-  if not _MODEL.value:
-    raise ValueError('`model` flag is required.')
+def main(argv: list[str]) -> None:
+  model_path = _MODEL.value or (
+      argv[1] if len(argv) > 1 and not argv[1].startswith('--') else None
+  )
+  if not model_path:
+    raise _app.UsageError('Please provide a model path argument or --model flag.')
   if not _OUTPUT.value:
-    raise ValueError('`output flag is required.')
+    raise _app.UsageError('`output` flag is required.')
 
   try:
-    data = parser.parse(_MODEL.value)
+    data = parser.parse(model_path)
     model = data.model
   except Exception as ex:  # pylint: disable=broad-except
-    print(f'Error loading model from `{_MODEL.value}`: {ex}')
+    print(f'Error loading model from `{model_path}`: {ex}')
     sys.exit(-1)
 
   for _ in range(_STEPS.value):
@@ -73,4 +74,4 @@ def main(argv):
 
 
 if __name__ == '__main__':
-  app.run(main)
+  _app.run(main)