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 numpy as onp
9import tyro
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(**onp.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 while True:
82 # Do nothing if no change.
83 time.sleep(0.02)
84 if not gui_elements.changed:
85 continue
86
87 gui_elements.changed = False
88
89 # Compute SMPL outputs.
90 smpl_outputs = model.get_outputs(
91 betas=np.array([x.value for x in gui_elements.gui_betas]),
92 joint_rotmats=tf.SO3.exp(
93 # (num_joints, 3)
94 np.array([x.value for x in gui_elements.gui_joints])
95 ).as_matrix(),
96 )
97 server.scene.add_mesh_simple(
98 "/human",
99 smpl_outputs.vertices,
100 smpl_outputs.faces,
101 wireframe=gui_elements.gui_wireframe.value,
102 color=gui_elements.gui_rgb.value,
103 )
104
105 # Match transform control gizmos to joint positions.
106 for i, control in enumerate(gui_elements.transform_controls):
107 control.position = smpl_outputs.T_parent_joint[i, :3, 3]
108
109
110@dataclass
111class GuiElements:
112 """Structure containing handles for reading from GUI elements."""
113
114 gui_rgb: viser.GuiInputHandle[tuple[int, int, int]]
115 gui_wireframe: viser.GuiInputHandle[bool]
116 gui_betas: list[viser.GuiInputHandle[float]]
117 gui_joints: list[viser.GuiInputHandle[tuple[float, float, float]]]
118 transform_controls: list[viser.TransformControlsHandle]
119
120 changed: bool
121 """This flag will be flipped to True whenever the mesh needs to be re-generated."""
122
123
124def make_gui_elements(
125 server: viser.ViserServer,
126 num_betas: int,
127 num_joints: int,
128 parent_idx: np.ndarray,
129) -> GuiElements:
130 """Make GUI elements for interacting with the model."""
131
132 tab_group = server.gui.add_tab_group()
133
134 def set_changed(_) -> None:
135 out.changed = True # out is define later!
136
137 # GUI elements: mesh settings + visibility.
138 with tab_group.add_tab("View", viser.Icon.VIEWFINDER):
139 gui_rgb = server.gui.add_rgb("Color", initial_value=(90, 200, 255))
140 gui_wireframe = server.gui.add_checkbox("Wireframe", initial_value=False)
141 gui_show_controls = server.gui.add_checkbox("Handles", initial_value=False)
142
143 gui_rgb.on_update(set_changed)
144 gui_wireframe.on_update(set_changed)
145
146 @gui_show_controls.on_update
147 def _(_):
148 for control in transform_controls:
149 control.visible = gui_show_controls.value
150
151 # GUI elements: shape parameters.
152 with tab_group.add_tab("Shape", viser.Icon.BOX):
153 gui_reset_shape = server.gui.add_button("Reset Shape")
154 gui_random_shape = server.gui.add_button("Random Shape")
155
156 @gui_reset_shape.on_click
157 def _(_):
158 for beta in gui_betas:
159 beta.value = 0.0
160
161 @gui_random_shape.on_click
162 def _(_):
163 for beta in gui_betas:
164 beta.value = onp.random.normal(loc=0.0, scale=1.0)
165
166 gui_betas = []
167 for i in range(num_betas):
168 beta = server.gui.add_slider(
169 f"beta{i}", min=-5.0, max=5.0, step=0.01, initial_value=0.0
170 )
171 gui_betas.append(beta)
172 beta.on_update(set_changed)
173
174 # GUI elements: joint angles.
175 with tab_group.add_tab("Joints", viser.Icon.ANGLE):
176 gui_reset_joints = server.gui.add_button("Reset Joints")
177 gui_random_joints = server.gui.add_button("Random Joints")
178
179 @gui_reset_joints.on_click
180 def _(_):
181 for joint in gui_joints:
182 joint.value = (0.0, 0.0, 0.0)
183
184 @gui_random_joints.on_click
185 def _(_):
186 for joint in gui_joints:
187 # It's hard to uniformly sample orientations directly in so(3), so we
188 # first sample on S^3 and then convert.
189 quat = onp.random.normal(loc=0.0, scale=1.0, size=(4,))
190 quat /= onp.linalg.norm(quat)
191 joint.value = tf.SO3(wxyz=quat).log()
192
193 gui_joints: list[viser.GuiInputHandle[tuple[float, float, float]]] = []
194 for i in range(num_joints):
195 gui_joint = server.gui.add_vector3(
196 label=f"Joint {i}",
197 initial_value=(0.0, 0.0, 0.0),
198 step=0.05,
199 )
200 gui_joints.append(gui_joint)
201
202 def set_callback_in_closure(i: int) -> None:
203 @gui_joint.on_update
204 def _(_):
205 transform_controls[i].wxyz = tf.SO3.exp(
206 np.array(gui_joints[i].value)
207 ).wxyz
208 out.changed = True
209
210 set_callback_in_closure(i)
211
212 # Transform control gizmos on joints.
213 transform_controls: list[viser.TransformControlsHandle] = []
214 prefixed_joint_names = [] # Joint names, but prefixed with parents.
215 for i in range(num_joints):
216 prefixed_joint_name = f"joint_{i}"
217 if i > 0:
218 prefixed_joint_name = (
219 prefixed_joint_names[parent_idx[i]] + "/" + prefixed_joint_name
220 )
221 prefixed_joint_names.append(prefixed_joint_name)
222 controls = server.scene.add_transform_controls(
223 f"/smpl/{prefixed_joint_name}",
224 depth_test=False,
225 scale=0.2 * (0.75 ** prefixed_joint_name.count("/")),
226 disable_axes=True,
227 disable_sliders=True,
228 visible=gui_show_controls.value,
229 )
230 transform_controls.append(controls)
231
232 def set_callback_in_closure(i: int) -> None:
233 @controls.on_update
234 def _(_) -> None:
235 axisangle = tf.SO3(transform_controls[i].wxyz).log()
236 gui_joints[i].value = (axisangle[0], axisangle[1], axisangle[2])
237
238 set_callback_in_closure(i)
239
240 out = GuiElements(
241 gui_rgb,
242 gui_wireframe,
243 gui_betas,
244 gui_joints,
245 transform_controls=transform_controls,
246 changed=True,
247 )
248 return out
249
250
251if __name__ == "__main__":
252 tyro.cli(main, description=__doc__)