SMPL visualizer (Skinned Mesh)ΒΆ
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
6from typing import List, Tuple
7
8import numpy as np
9import tyro
10import viser
11import viser.transforms as tf
12
13
14@dataclass(frozen=True)
15class SmplFkOutputs:
16 T_world_joint: np.ndarray # (num_joints, 4, 4)
17 T_parent_joint: np.ndarray # (num_joints, 4, 4)
18
19
20class SmplHelper:
21 """Helper for models in the SMPL family, implemented in numpy. Does not include blend skinning."""
22
23 def __init__(self, model_path: Path) -> None:
24 assert model_path.suffix.lower() == ".npz", "Model should be an .npz file!"
25 body_dict = dict(**np.load(model_path, allow_pickle=True))
26
27 self.J_regressor = body_dict["J_regressor"]
28 self.weights = body_dict["weights"]
29 self.v_template = body_dict["v_template"]
30 self.posedirs = body_dict["posedirs"]
31 self.shapedirs = body_dict["shapedirs"]
32 self.faces = body_dict["f"]
33
34 self.num_joints: int = self.weights.shape[-1]
35 self.num_betas: int = self.shapedirs.shape[-1]
36 self.parent_idx: np.ndarray = body_dict["kintree_table"][0]
37
38 def get_tpose(self, betas: np.ndarray) -> tuple[np.ndarray, np.ndarray]:
39 # Get shaped vertices + joint positions, when all local poses are identity.
40 v_tpose = self.v_template + np.einsum("vxb,b->vx", self.shapedirs, betas)
41 j_tpose = np.einsum("jv,vx->jx", self.J_regressor, v_tpose)
42 return v_tpose, j_tpose
43
44 def get_outputs(
45 self, betas: np.ndarray, joint_rotmats: np.ndarray
46 ) -> SmplFkOutputs:
47 # Get shaped vertices + joint positions, when all local poses are identity.
48 v_tpose = self.v_template + np.einsum("vxb,b->vx", self.shapedirs, betas)
49 j_tpose = np.einsum("jv,vx->jx", self.J_regressor, v_tpose)
50
51 # Local SE(3) transforms.
52 T_parent_joint = np.zeros((self.num_joints, 4, 4)) + np.eye(4)
53 T_parent_joint[:, :3, :3] = joint_rotmats
54 T_parent_joint[0, :3, 3] = j_tpose[0]
55 T_parent_joint[1:, :3, 3] = j_tpose[1:] - j_tpose[self.parent_idx[1:]]
56
57 # Forward kinematics.
58 T_world_joint = T_parent_joint.copy()
59 for i in range(1, self.num_joints):
60 T_world_joint[i] = T_world_joint[self.parent_idx[i]] @ T_parent_joint[i]
61
62 return SmplFkOutputs(T_world_joint, T_parent_joint)
63
64
65def main(model_path: Path) -> None:
66 server = viser.ViserServer()
67 server.scene.set_up_direction("+y")
68 server.gui.configure_theme(control_layout="collapsible")
69
70 # Main loop. We'll read pose/shape from the GUI elements, compute the mesh,
71 # and then send the updated mesh in a loop.
72 model = SmplHelper(model_path)
73 gui_elements = make_gui_elements(
74 server,
75 num_betas=model.num_betas,
76 num_joints=model.num_joints,
77 parent_idx=model.parent_idx,
78 )
79 v_tpose, j_tpose = model.get_tpose(np.zeros((model.num_betas,)))
80 mesh_handle = server.scene.add_mesh_skinned(
81 "/human",
82 v_tpose,
83 model.faces,
84 bone_wxyzs=tf.SO3.identity(batch_axes=(model.num_joints,)).wxyz,
85 bone_positions=j_tpose,
86 skin_weights=model.weights,
87 wireframe=gui_elements.gui_wireframe.value,
88 color=gui_elements.gui_rgb.value,
89 )
90
91 while True:
92 # Do nothing if no change.
93 time.sleep(0.02)
94 if not gui_elements.changed:
95 continue
96
97 # Shapes changed: update vertices / joint positions.
98 if gui_elements.betas_changed:
99 v_tpose, j_tpose = model.get_tpose(
100 np.array([gui_beta.value for gui_beta in gui_elements.gui_betas])
101 )
102 mesh_handle.vertices = v_tpose
103 mesh_handle.bone_positions = j_tpose
104
105 gui_elements.changed = False
106 gui_elements.betas_changed = False
107
108 # Render as wireframe?
109 mesh_handle.wireframe = gui_elements.gui_wireframe.value
110
111 # Compute SMPL outputs.
112 smpl_outputs = model.get_outputs(
113 betas=np.array([x.value for x in gui_elements.gui_betas]),
114 joint_rotmats=np.stack(
115 [
116 tf.SO3.exp(np.array(x.value)).as_matrix()
117 for x in gui_elements.gui_joints
118 ],
119 axis=0,
120 ),
121 )
122
123 # Match transform control gizmos to joint positions.
124 for i, control in enumerate(gui_elements.transform_controls):
125 control.position = smpl_outputs.T_parent_joint[i, :3, 3]
126 mesh_handle.bones[i].wxyz = tf.SO3.from_matrix(
127 smpl_outputs.T_world_joint[i, :3, :3]
128 ).wxyz
129 mesh_handle.bones[i].position = smpl_outputs.T_world_joint[i, :3, 3]
130
131
132@dataclass
133class GuiElements:
134 """Structure containing handles for reading from GUI elements."""
135
136 gui_rgb: viser.GuiInputHandle[Tuple[int, int, int]]
137 gui_wireframe: viser.GuiInputHandle[bool]
138 gui_betas: List[viser.GuiInputHandle[float]]
139 gui_joints: List[viser.GuiInputHandle[Tuple[float, float, float]]]
140 transform_controls: List[viser.TransformControlsHandle]
141
142 changed: bool
143 """This flag will be flipped to True whenever any input is changed."""
144
145 betas_changed: bool
146 """This flag will be flipped to True whenever the shape changes."""
147
148
149def make_gui_elements(
150 server: viser.ViserServer,
151 num_betas: int,
152 num_joints: int,
153 parent_idx: np.ndarray,
154) -> GuiElements:
155 """Make GUI elements for interacting with the model."""
156
157 tab_group = server.gui.add_tab_group()
158
159 def set_changed(_) -> None:
160 out.changed = True # out is defined later!
161
162 def set_betas_changed(_) -> None:
163 out.betas_changed = True
164 out.changed = True
165
166 # GUI elements: mesh settings + visibility.
167 with tab_group.add_tab("View", viser.Icon.VIEWFINDER):
168 gui_rgb = server.gui.add_rgb("Color", initial_value=(90, 200, 255))
169 gui_wireframe = server.gui.add_checkbox("Wireframe", initial_value=False)
170 gui_show_controls = server.gui.add_checkbox("Handles", initial_value=True)
171 gui_control_size = server.gui.add_slider(
172 "Handle size", min=0.0, max=10.0, step=0.01, initial_value=1.0
173 )
174
175 gui_rgb.on_update(set_changed)
176 gui_wireframe.on_update(set_changed)
177
178 @gui_show_controls.on_update
179 def _(_):
180 for control in transform_controls:
181 control.visible = gui_show_controls.value
182
183 @gui_control_size.on_update
184 def _(_):
185 for control in transform_controls:
186 prefixed_joint_name = control.name
187 control.scale = (
188 0.2
189 * (0.75 ** prefixed_joint_name.count("/"))
190 * gui_control_size.value
191 )
192
193 # GUI elements: shape parameters.
194 with tab_group.add_tab("Shape", viser.Icon.BOX):
195 gui_reset_shape = server.gui.add_button("Reset Shape")
196 gui_random_shape = server.gui.add_button("Random Shape")
197
198 @gui_reset_shape.on_click
199 def _(_):
200 for beta in gui_betas:
201 beta.value = 0.0
202
203 @gui_random_shape.on_click
204 def _(_):
205 for beta in gui_betas:
206 beta.value = np.random.normal(loc=0.0, scale=1.0)
207
208 gui_betas = []
209 for i in range(num_betas):
210 beta = server.gui.add_slider(
211 f"beta{i}", min=-5.0, max=5.0, step=0.01, initial_value=0.0
212 )
213 gui_betas.append(beta)
214 beta.on_update(set_betas_changed)
215
216 # GUI elements: joint angles.
217 with tab_group.add_tab("Joints", viser.Icon.ANGLE):
218 gui_reset_joints = server.gui.add_button("Reset Joints")
219 gui_random_joints = server.gui.add_button("Random Joints")
220
221 @gui_reset_joints.on_click
222 def _(_):
223 for joint in gui_joints:
224 joint.value = (0.0, 0.0, 0.0)
225
226 @gui_random_joints.on_click
227 def _(_):
228 rng = np.random.default_rng()
229 for joint in gui_joints:
230 joint.value = tf.SO3.sample_uniform(rng).log()
231
232 gui_joints: List[viser.GuiInputHandle[Tuple[float, float, float]]] = []
233 for i in range(num_joints):
234 gui_joint = server.gui.add_vector3(
235 label=f"Joint {i}",
236 initial_value=(0.0, 0.0, 0.0),
237 step=0.05,
238 )
239 gui_joints.append(gui_joint)
240
241 def set_callback_in_closure(i: int) -> None:
242 @gui_joint.on_update
243 def _(_):
244 transform_controls[i].wxyz = tf.SO3.exp(
245 np.array(gui_joints[i].value)
246 ).wxyz
247 out.changed = True
248
249 set_callback_in_closure(i)
250
251 # Transform control gizmos on joints.
252 transform_controls: List[viser.TransformControlsHandle] = []
253 prefixed_joint_names = [] # Joint names, but prefixed with parents.
254 for i in range(num_joints):
255 prefixed_joint_name = f"joint_{i}"
256 if i > 0:
257 prefixed_joint_name = (
258 prefixed_joint_names[parent_idx[i]] + "/" + prefixed_joint_name
259 )
260 prefixed_joint_names.append(prefixed_joint_name)
261 controls = server.scene.add_transform_controls(
262 f"/smpl/{prefixed_joint_name}",
263 depth_test=False,
264 scale=0.2 * (0.75 ** prefixed_joint_name.count("/")),
265 disable_axes=True,
266 disable_sliders=True,
267 visible=gui_show_controls.value,
268 )
269 transform_controls.append(controls)
270
271 def set_callback_in_closure(i: int) -> None:
272 @controls.on_update
273 def _(_) -> None:
274 axisangle = tf.SO3(transform_controls[i].wxyz).log()
275 gui_joints[i].value = (axisangle[0], axisangle[1], axisangle[2])
276
277 set_callback_in_closure(i)
278
279 out = GuiElements(
280 gui_rgb,
281 gui_wireframe,
282 gui_betas,
283 gui_joints,
284 transform_controls=transform_controls,
285 changed=True,
286 betas_changed=False,
287 )
288 return out
289
290
291if __name__ == "__main__":
292 tyro.cli(main, description=__doc__)