SMPL model visualizerΒΆ

Visualizer for SMPL human body models. Requires a .npz model file.

See here for download instructions:

https://github.com/vchoutas/smplx?tab=readme-ov-file#downloading-the-model

  1from __future__ import annotations
  2
  3import time
  4from dataclasses import dataclass
  5from pathlib import Path
  6
  7import numpy as np
  8import tyro
  9
 10import viser
 11import viser.transforms as tf
 12
 13
 14@dataclass(frozen=True)
 15class SmplOutputs:
 16    vertices: np.ndarray
 17    faces: np.ndarray
 18    T_world_joint: np.ndarray  # (num_joints, 4, 4)
 19    T_parent_joint: np.ndarray  # (num_joints, 4, 4)
 20
 21
 22class SmplHelper:
 23    """Helper for models in the SMPL family, implemented in numpy."""
 24
 25    def __init__(self, model_path: Path) -> None:
 26        assert model_path.suffix.lower() == ".npz", "Model should be an .npz file!"
 27        body_dict = dict(**np.load(model_path, allow_pickle=True))
 28
 29        self.J_regressor = body_dict["J_regressor"]
 30        self.weights = body_dict["weights"]
 31        self.v_template = body_dict["v_template"]
 32        self.posedirs = body_dict["posedirs"]
 33        self.shapedirs = body_dict["shapedirs"]
 34        self.faces = body_dict["f"]
 35
 36        self.num_joints: int = self.weights.shape[-1]
 37        self.num_betas: int = self.shapedirs.shape[-1]
 38        self.parent_idx: np.ndarray = body_dict["kintree_table"][0]
 39
 40    def get_outputs(self, betas: np.ndarray, joint_rotmats: np.ndarray) -> SmplOutputs:
 41        # Get shaped vertices + joint positions, when all local poses are identity.
 42        v_tpose = self.v_template + np.einsum("vxb,b->vx", self.shapedirs, betas)
 43        j_tpose = np.einsum("jv,vx->jx", self.J_regressor, v_tpose)
 44
 45        # Local SE(3) transforms.
 46        T_parent_joint = np.zeros((self.num_joints, 4, 4)) + np.eye(4)
 47        T_parent_joint[:, :3, :3] = joint_rotmats
 48        T_parent_joint[0, :3, 3] = j_tpose[0]
 49        T_parent_joint[1:, :3, 3] = j_tpose[1:] - j_tpose[self.parent_idx[1:]]
 50
 51        # Forward kinematics.
 52        T_world_joint = T_parent_joint.copy()
 53        for i in range(1, self.num_joints):
 54            T_world_joint[i] = T_world_joint[self.parent_idx[i]] @ T_parent_joint[i]
 55
 56        # Linear blend skinning.
 57        pose_delta = (joint_rotmats[1:, ...] - np.eye(3)).flatten()
 58        v_blend = v_tpose + np.einsum("byn,n->by", self.posedirs, pose_delta)
 59        v_delta = np.ones((v_blend.shape[0], self.num_joints, 4))
 60        v_delta[:, :, :3] = v_blend[:, None, :] - j_tpose[None, :, :]
 61        v_posed = np.einsum(
 62            "jxy,vj,vjy->vx", T_world_joint[:, :3, :], self.weights, v_delta
 63        )
 64        return SmplOutputs(v_posed, self.faces, T_world_joint, T_parent_joint)
 65
 66
 67def main(model_path: Path) -> None:
 68    server = viser.ViserServer()
 69    server.scene.set_up_direction("+y")
 70    server.gui.configure_theme(control_layout="collapsible")
 71
 72    # Main loop. We'll read pose/shape from the GUI elements, compute the mesh,
 73    # and then send the updated mesh in a loop.
 74    model = SmplHelper(model_path)
 75    gui_elements = make_gui_elements(
 76        server,
 77        num_betas=model.num_betas,
 78        num_joints=model.num_joints,
 79        parent_idx=model.parent_idx,
 80    )
 81    body_handle = server.scene.add_mesh_simple(
 82        "/human",
 83        model.v_template,
 84        model.faces,
 85        wireframe=gui_elements.gui_wireframe.value,
 86        color=gui_elements.gui_rgb.value,
 87    )
 88    while True:
 89        # Do nothing if no change.
 90        time.sleep(0.02)
 91        if not gui_elements.changed:
 92            continue
 93
 94        gui_elements.changed = False
 95
 96        # If anything has changed, re-compute SMPL outputs.
 97        smpl_outputs = model.get_outputs(
 98            betas=np.array([x.value for x in gui_elements.gui_betas]),
 99            joint_rotmats=tf.SO3.exp(
100                # (num_joints, 3)
101                np.array([x.value for x in gui_elements.gui_joints])
102            ).as_matrix(),
103        )
104
105        # Update the mesh properties based on the SMPL model output + GUI
106        # elements.
107        body_handle.vertices = smpl_outputs.vertices
108        body_handle.wireframe = gui_elements.gui_wireframe.value
109        body_handle.color = gui_elements.gui_rgb.value
110
111        # Match transform control gizmos to joint positions.
112        for i, control in enumerate(gui_elements.transform_controls):
113            control.position = smpl_outputs.T_parent_joint[i, :3, 3]
114
115
116@dataclass
117class GuiElements:
118    """Structure containing handles for reading from GUI elements."""
119
120    gui_rgb: viser.GuiInputHandle[tuple[int, int, int]]
121    gui_wireframe: viser.GuiInputHandle[bool]
122    gui_betas: list[viser.GuiInputHandle[float]]
123    gui_joints: list[viser.GuiInputHandle[tuple[float, float, float]]]
124    transform_controls: list[viser.TransformControlsHandle]
125
126    changed: bool
127    """This flag will be flipped to True whenever the mesh needs to be re-generated."""
128
129
130def make_gui_elements(
131    server: viser.ViserServer,
132    num_betas: int,
133    num_joints: int,
134    parent_idx: np.ndarray,
135) -> GuiElements:
136    """Make GUI elements for interacting with the model."""
137
138    tab_group = server.gui.add_tab_group()
139
140    def set_changed(_) -> None:
141        out.changed = True  # out is define later!
142
143    # GUI elements: mesh settings + visibility.
144    with tab_group.add_tab("View", viser.Icon.VIEWFINDER):
145        gui_rgb = server.gui.add_rgb("Color", initial_value=(90, 200, 255))
146        gui_wireframe = server.gui.add_checkbox("Wireframe", initial_value=False)
147        gui_show_controls = server.gui.add_checkbox("Handles", initial_value=True)
148
149        gui_rgb.on_update(set_changed)
150        gui_wireframe.on_update(set_changed)
151
152        @gui_show_controls.on_update
153        def _(_):
154            for control in transform_controls:
155                control.visible = gui_show_controls.value
156
157    # GUI elements: shape parameters.
158    with tab_group.add_tab("Shape", viser.Icon.BOX):
159        gui_reset_shape = server.gui.add_button("Reset Shape")
160        gui_random_shape = server.gui.add_button("Random Shape")
161
162        @gui_reset_shape.on_click
163        def _(_):
164            for beta in gui_betas:
165                beta.value = 0.0
166
167        @gui_random_shape.on_click
168        def _(_):
169            for beta in gui_betas:
170                beta.value = np.random.normal(loc=0.0, scale=1.0)
171
172        gui_betas = []
173        for i in range(num_betas):
174            beta = server.gui.add_slider(
175                f"beta{i}", min=-5.0, max=5.0, step=0.01, initial_value=0.0
176            )
177            gui_betas.append(beta)
178            beta.on_update(set_changed)
179
180    # GUI elements: joint angles.
181    with tab_group.add_tab("Joints", viser.Icon.ANGLE):
182        gui_reset_joints = server.gui.add_button("Reset Joints")
183        gui_random_joints = server.gui.add_button("Random Joints")
184
185        @gui_reset_joints.on_click
186        def _(_):
187            for joint in gui_joints:
188                joint.value = (0.0, 0.0, 0.0)
189
190        @gui_random_joints.on_click
191        def _(_):
192            rng = np.random.default_rng()
193            for joint in gui_joints:
194                joint.value = tf.SO3.sample_uniform(rng).log()
195
196        gui_joints: list[viser.GuiInputHandle[tuple[float, float, float]]] = []
197        for i in range(num_joints):
198            gui_joint = server.gui.add_vector3(
199                label=f"Joint {i}",
200                initial_value=(0.0, 0.0, 0.0),
201                step=0.05,
202            )
203            gui_joints.append(gui_joint)
204
205            def set_callback_in_closure(i: int) -> None:
206                @gui_joint.on_update
207                def _(_):
208                    transform_controls[i].wxyz = tf.SO3.exp(
209                        np.array(gui_joints[i].value)
210                    ).wxyz
211                    out.changed = True
212
213            set_callback_in_closure(i)
214
215    # Transform control gizmos on joints.
216    transform_controls: list[viser.TransformControlsHandle] = []
217    prefixed_joint_names = []  # Joint names, but prefixed with parents.
218    for i in range(num_joints):
219        prefixed_joint_name = f"joint_{i}"
220        if i > 0:
221            prefixed_joint_name = (
222                prefixed_joint_names[parent_idx[i]] + "/" + prefixed_joint_name
223            )
224        prefixed_joint_names.append(prefixed_joint_name)
225        controls = server.scene.add_transform_controls(
226            f"/smpl/{prefixed_joint_name}",
227            depth_test=False,
228            scale=0.2 * (0.75 ** prefixed_joint_name.count("/")),
229            disable_axes=True,
230            disable_sliders=True,
231            visible=gui_show_controls.value,
232        )
233        transform_controls.append(controls)
234
235        def set_callback_in_closure(i: int) -> None:
236            @controls.on_update
237            def _(_) -> None:
238                axisangle = tf.SO3(transform_controls[i].wxyz).log()
239                gui_joints[i].value = (axisangle[0], axisangle[1], axisangle[2])
240
241        set_callback_in_closure(i)
242
243    out = GuiElements(
244        gui_rgb,
245        gui_wireframe,
246        gui_betas,
247        gui_joints,
248        transform_controls=transform_controls,
249        changed=True,
250    )
251    return out
252
253
254if __name__ == "__main__":
255    tyro.cli(main, description=__doc__)