[Diffusion] DreamZero world model integration with CFG parallel + OpenPI serving (#2162)

Signed-off-by: Meng <meng_chen99@163.com>
Signed-off-by: Yangshen Deng <yangshen.d@outlook.com>
Signed-off-by: Suli Wang <50828270+wsl2000@users.noreply.github.com>
Co-authored-by: Meng <meng_chen99@163.com>
Co-authored-by: Suli Wang <50828270+wsl2000@users.noreply.github.com>
Co-authored-by: amy-why-3459 <wuhaiyan17@huawei.com>

examples/online_serving/dreamzero/README.md

@@ -0,0 +1,132 @@
+# DreamZero
+
+DreamZero is the robot-policy serving example for the OpenPI-compatible `/v1/realtime/robot/openpi` endpoint.
+
+## Supported checkpoints
+
+| Model | HuggingFace repo |
+|---|---|
+| DreamZero-DROID | `GEAR-Dreams/DreamZero-DROID` |
+
+## Quick start
+
+### Start the server
+
+```bash
+bash examples/online_serving/dreamzero/run_server.sh
+```
+
+By default this launches:
+
+```bash
+vllm serve GEAR-Dreams/DreamZero-DROID --omni --port 8000 \
+    --served-model-name dreamzero-droid \
+    --deploy-config vllm_omni/deploy/dreamzero_tp1_cfg2.yaml \
+    --enforce-eager --disable-log-stats
+```
+
+Override `MODEL`, `PORT`, `HOST`, `DEPLOY_CONFIG`, or `SERVED_MODEL_NAME` through the script environment if needed.
+
+### Install example dependencies
+
+The core `pip install -e .` setup does not include the extra packages used by the DreamZero example scripts.
+
+- `openpi_client.py`:
+  `openpi-client`, `websockets`, `opencv-python`
+- `droid_sim_eval_client.py`:
+  `mediapy`, `websockets`, `openpi-client`
+
+The DROID sim-eval script also needs an Isaac Lab environment that provides `isaaclab`, `isaaclab_tasks`, `sim_evals`, and `gymnasium`.
+
+If you run the DROID client on Python < 3.12, also install `typing-extensions`.
+
+### Configure TP and CFG parallelism
+
+The bundled DreamZero configs intentionally keep only:
+
+| Config | Purpose |
+|---|---|
+| `vllm_omni/deploy/dreamzero.yaml` | Default TP=1, CFG parallel disabled |
+| `vllm_omni/deploy/dreamzero_tp1_cfg2.yaml` | TP=1, CFG parallel size=2 |
+
+For other topologies, use CLI parallelism flags and update stage 0 `devices` with `--stage-overrides`. The number of listed devices must match `tensor_parallel_size * cfg_parallel_size`.
+
+TP=2 with CFG parallel disabled:
+
+```bash
+vllm serve GEAR-Dreams/DreamZero-DROID --omni --port 8000 \
+    --served-model-name dreamzero-droid \
+    --deploy-config vllm_omni/deploy/dreamzero.yaml \
+    --tensor-parallel-size 2 \
+    --stage-overrides '{"0": {"devices": "0,1"}}' \
+    --enforce-eager --disable-log-stats
+```
+
+TP=2 with CFG parallel size=2:
+
+```bash
+vllm serve GEAR-Dreams/DreamZero-DROID --omni --port 8000 \
+    --served-model-name dreamzero-droid \
+    --deploy-config vllm_omni/deploy/dreamzero.yaml \
+    --tensor-parallel-size 2 \
+    --cfg-parallel-size 2 \
+    --stage-overrides '{"0": {"devices": "0,1,2,3"}}' \
+    --enforce-eager --disable-log-stats
+```
+
+### Download example assets
+
+The OpenPI client and DROID sim-eval example expect the three camera MP4 files in `outputs/dreamzero/assets`.
+
+```bash
+hf download YangshenDeng/vllm-omni-dreamzero-assets --repo-type dataset --local-dir outputs/dreamzero/assets
+```
+
+### Run the OpenPI client
+
+```bash
+python examples/online_serving/dreamzero/openpi_client.py \
+    --host 127.0.0.1 \
+    --port 8000 \
+    --video-dir outputs/dreamzero/assets
+```
+
+This client uses downloaded example videos and talks to the OpenPI websocket server.
+
+### Run DROID sim eval
+
+```bash
+${ISAACLAB_LAUNCHER} -p examples/online_serving/dreamzero/droid_sim_eval_client.py \
+    --host 127.0.0.1 \
+    --port 8000 \
+    --scene 1 \
+    --episodes 1 \
+    --headless \
+    --device cuda:0
+```
+
+Set `ISAACLAB_LAUNCHER=path/to/isaaclab.sh` from the vLLM-Omni repository root before running the command.
+This launches Isaac Lab / sim-evals and runs the DROID benchmark loop against the same websocket endpoint.
+
+### Export comparison videos offline
+
+```bash
+python examples/offline_inference/dreamzero/export_prediction_video.py \
+    --deploy-config vllm_omni/deploy/dreamzero_tp1_cfg2.yaml \
+    --save-input-video \
+    --save-gif
+```
+
+The export script uses local `Omni` inference, not the websocket server. It writes the input rollout video and the predicted output video artifacts for side-by-side inspection.
+
+### MolmoSpace demo
+
+```bash
+python examples/online_serving/dreamzero/molmospace_dreamzero_eval_demo.py \
+    --host 127.0.0.1 \
+    --port 8000 \
+    --benchmark_dir /path/to/benchmark \
+    --output_dir /path/to/output
+```
+
+This demo adapts DreamZero to the MolmoSpace-style remote policy eval loop.