[BUG FIX] Fix default visualization mode for emitter surface. (#1665)

* Fix default visualization mode for emitter surface
* Fix PBD set velocity
* Add runtime check for emitter visualisation mode
* Add runtime check for MPM grid size
* Add unit test for fluid emitter
* Fix and improve example 'water_wheel.py'

Author: duburcqa

examples/coupling/water_wheel.py

@@ -7,6 +7,8 @@
 
 def main():
     parser = argparse.ArgumentParser()
+    parser.add_argument("--solver", type=str, default="sph", choices=("sph", "mpm"))
+    parser.add_argument("--recon", action="store_true", default=False)
     parser.add_argument("-v", "--vis", action="store_true", default=False)
     args = parser.parse_args()
 
@@ -20,8 +22,14 @@ def main():
             substeps=10,
         ),
         mpm_options=gs.options.MPMOptions(
-            lower_bound=(0.0, 0.0, 0.0),
-            upper_bound=(1.0, 1.0, 1.5),
+            lower_bound=(0.0, -1.5, 0.0),
+            upper_bound=(1.0, 1.5, 4.0),
+        ),
+        sph_options=gs.options.SPHOptions(
+            particle_size=0.02,
+        ),
+        pbd_options=gs.options.PBDOptions(
+            particle_size=0.02,
         ),
         viewer_options=gs.options.ViewerOptions(
             camera_pos=(5.5, 6.5, 3.2),
@@ -33,13 +41,10 @@ def main():
             rendered_envs_idx=[0],
         ),
         show_viewer=args.vis,
-        sph_options=gs.options.SPHOptions(
-            particle_size=0.02,
-        ),
     )
 
     plane = scene.add_entity(gs.morphs.Plane())
-    wheel_0 = scene.add_entity(
+    wheel = scene.add_entity(
         morph=gs.morphs.URDF(
             file="urdf/wheel/fancy_wheel.urdf",
             pos=(0.5, 0.25, 1.6),
@@ -50,17 +55,19 @@ def main():
     )
 
     emitter = scene.add_emitter(
-        material=gs.materials.SPH.Liquid(sampler="regular"),
+        material=getattr(gs.materials, args.solver.upper()).Liquid(
+            sampler="regular",
+        ),
         max_particles=100000,
         surface=gs.surfaces.Glass(
             color=(0.7, 0.85, 1.0, 0.7),
+            vis_mode="recon" if args.recon else "particle",
         ),
     )
-    scene.build(n_envs=5)
+    scene.build(n_envs=2)
 
     horizon = 500
     for i in range(horizon):
-        print(i)
         emitter.emit(
             pos=np.array([0.5, 1.0, 3.5]),
             direction=np.array([0.0, 0, -1.0]),

examples/pbd_liquid.py

@@ -17,24 +17,29 @@ def main():
         sim_options=gs.options.SimOptions(
             dt=2e-3,
         ),
-        viewer_options=gs.options.ViewerOptions(
-            camera_pos=(3.5, 1.0, 2.5),
-            camera_lookat=(0.0, 0.0, 0.5),
-            camera_fov=40,
-        ),
-        show_viewer=False,
         pbd_options=gs.options.PBDOptions(
             lower_bound=(0.0, 0.0, 0.0),
             upper_bound=(1.0, 1.0, 1.0),
             max_density_solver_iterations=10,
             max_viscosity_solver_iterations=1,
         ),
+        viewer_options=gs.options.ViewerOptions(
+            camera_pos=(3.5, 1.0, 2.5),
+            camera_lookat=(0.0, 0.0, 0.5),
+            camera_fov=40,
+        ),
+        show_viewer=args.vis,
     )
 
     ########################## entities ##########################
 
     liquid = scene.add_entity(
-        material=gs.materials.PBD.Liquid(rho=1.0, density_relaxation=1.0, viscosity_relaxation=0.0, sampler="regular"),
+        material=gs.materials.PBD.Liquid(
+            sampler="regular",
+            rho=1.0,
+            density_relaxation=1.0,
+            viscosity_relaxation=0.0,
+        ),
         morph=gs.morphs.Box(lower=(0.2, 0.1, 0.1), upper=(0.4, 0.3, 0.5)),
     )
     scene.build(n_envs=5)

genesis/engine/entities/particle_entity.py

@@ -243,8 +243,8 @@ def sample(self):
 
         if isinstance(self._morph, gs.options.morphs.Nowhere):
             origin = gu.nowhere()
-            self._vverts = np.array([], dtype=gs.np_float)
-            self._vfaces = np.array([], dtype=gs.np_float)
+            self._vverts = np.zeros((0, 3), dtype=gs.np_float)
+            self._vfaces = np.zeros((0, 3), dtype=gs.np_float)
         elif isinstance(self._morph, gs.options.morphs.MeshSet):
             for i in range(len(self._morph.files)):
                 pos_i = np.asarray(self._morph.poss[i], dtype=gs.np_float)

genesis/engine/scene.py

@@ -333,7 +333,7 @@ def add_entity(
             if surface.vis_mode is None:
                 surface.vis_mode = "visual"
 
-            if surface.vis_mode not in ["visual", "collision", "sdf"]:
+            if surface.vis_mode not in ("visual", "collision", "sdf"):
                 gs.raise_exception(
                     f"Unsupported `surface.vis_mode` for material {material}: '{surface.vis_mode}'. Expected one of: ['visual', 'collision', 'sdf']."
                 )
@@ -352,7 +352,7 @@ def add_entity(
             if surface.vis_mode is None:
                 surface.vis_mode = "particle"
 
-            if surface.vis_mode not in ["particle", "recon"]:
+            if surface.vis_mode not in ("particle", "recon"):
                 gs.raise_exception(
                     f"Unsupported `surface.vis_mode` for material {material}: '{surface.vis_mode}'. Expected one of: ['particle', 'recon']."
                 )
@@ -370,7 +370,7 @@ def add_entity(
             if surface.vis_mode is None:
                 surface.vis_mode = "visual"
 
-            if surface.vis_mode not in ["visual", "particle", "recon"]:
+            if surface.vis_mode not in ("visual", "particle", "recon"):
                 gs.raise_exception(
                     f"Unsupported `surface.vis_mode` for material {material}: '{surface.vis_mode}'. Expected one of: ['visual', 'particle', 'recon']."
                 )
@@ -612,11 +612,13 @@ def add_emitter(
         Parameters
         ----------
         material : gs.materials.Material
-            The material of the fluid to be emitted. Must be an instance of `gs.materials.MPM.Base` or `gs.materials.SPH.Base`.
+            The material of the fluid to be emitted. Must be an instance of `gs.materials.MPM.Base`,
+            `gs.materials.SPH.Base`, `gs.materials.PBD.Particle` or `gs.materials.PBD.Liquid`.
         max_particles : int
-            The maximum number of particles that can be emitted by the emitter. Particles will be recycled once this limit is reached.
+            The maximum number of particles that can be emitted by the emitter. Particles will be recycled once this
+            limit is reached.
         surface : gs.surfaces.Surface | None, optional
-            The surface of the emitter. If None, use ``gs.surfaces.Default(color=(0.6, 0.8, 1.0, 1.0))``.
+            The surface of the emitter. If None, use `gs.surfaces.Default(color=(0.6, 0.8, 1.0, 1.0))`.
 
         Returns
         -------
@@ -631,12 +633,18 @@ def add_emitter(
             material, (gs.materials.MPM.Base, gs.materials.SPH.Base, gs.materials.PBD.Particle, gs.materials.PBD.Liquid)
         ):
             gs.raise_exception(
-                "Non-supported material for emitter. Supported materials are: `gs.materials.MPM.Base`, `gs.materials.SPH.Base`, `gs.materials.PBD.Particle`, `gs.materials.PBD.Liquid`."
+                "Non-supported material for emitter. Supported materials are: `gs.materials.MPM.Base`, "
+                "`gs.materials.SPH.Base`, `gs.materials.PBD.Particle`, `gs.materials.PBD.Liquid`."
             )
 
         if surface is None:
             surface = gs.surfaces.Default(color=(0.6, 0.8, 1.0, 1.0))
 
+        if surface.vis_mode is None:
+            surface.vis_mode = "particle"
+        if surface.vis_mode == "visual":
+            gs.raise_exception("surface.vis_mode='visual' is not supported for fluid emitters.")
+
         emitter = Emitter(max_particles)
         entity = self.add_entity(
             morph=gs.morphs.Nowhere(n_particles=max_particles),

genesis/engine/solvers/mpm_solver.py

@@ -1,15 +1,16 @@
 from typing import TYPE_CHECKING
+
 import numpy as np
 import gstaichi as ti
 import torch
 
 import genesis as gs
-from genesis.options.solvers import MPMOptions
 import genesis.utils.geom as gu
+import genesis.utils.sdf_decomp as sdf_decomp
 from genesis.engine.boundaries import CubeBoundary
 from genesis.engine.entities import MPMEntity
 from genesis.engine.states.solvers import MPMSolverState
-import genesis.utils.sdf_decomp as sdf_decomp
+from genesis.options.solvers import MPMOptions
 
 from .base_solver import Solver
 
@@ -59,6 +60,11 @@ def __init__(self, scene: "Scene", sim: "Simulator", options: "MPMOptions"):
 
             if sim.requires_grad:
                 gs.raise_exception("Sparse grid is not supported in differentiable mode.")
+        if np.prod(self._grid_res) > 1e9:
+            gs.raise_exception(
+                "Grid size larger than 1e9 not supported by MPM solver. Please reduce 'grid_density', or set tighter "
+                "boundaries via 'lower_bound' / 'upper_bound'."
+            )
 
         # materials
         self._mats = list()
@@ -146,8 +152,8 @@ def init_particle_fields(self):
 
     def init_grid_fields(self):
         grid_cell_state = ti.types.struct(
-            vel_in=gs.ti_vec3,  # input momentum/velocity
             mass=gs.ti_float,  # mass
+            vel_in=gs.ti_vec3,  # input momentum/velocity
             vel_out=gs.ti_vec3,  # output momentum/velocity
         )
 

genesis/engine/solvers/pbd_solver.py

@@ -854,7 +854,7 @@ def _kernel_set_particles_vel(
         for i_p, i_b in ti.ndrange(n_particles, self._B):
             i_global = i_p + particle_start
             for k in ti.static(range(3)):
-                self.particles[i_global, i_b].vel[k] = vel[i_p, k]
+                self.particles[i_global, i_b].vel[k] = vel[i_b, i_p, k]
 
     @ti.kernel
     def _kernel_set_particles_active(

tests/test_hybrid.py

@@ -73,3 +73,63 @@ def test_rigid_mpm_muscle(show_viewer):
 
     with np.testing.assert_raises(AssertionError):
         assert_allclose(ball.get_pos(), ball_pos_init, atol=1e-2)
+
+
+@pytest.mark.required
+@pytest.mark.parametrize(
+    "material_type",
+    [
+        gs.materials.PBD.Liquid,
+        gs.materials.SPH.Liquid,
+        gs.materials.MPM.Liquid,
+        gs.materials.MPM.Sand,
+        gs.materials.MPM.Snow,
+        gs.materials.MPM.Elastic,  # This makes little sense but nothing prevents doing this
+    ],
+)
+def test_fluid_emitter(material_type, show_viewer):
+    scene = gs.Scene(
+        sim_options=gs.options.SimOptions(
+            dt=4e-3,
+            substeps=10,
+        ),
+        mpm_options=gs.options.MPMOptions(
+            lower_bound=(0.0, -1.5, 0.0),
+            upper_bound=(1.0, 1.5, 4.0),
+        ),
+        sph_options=gs.options.SPHOptions(
+            particle_size=0.02,
+        ),
+        pbd_options=gs.options.PBDOptions(
+            particle_size=0.02,
+        ),
+        viewer_options=gs.options.ViewerOptions(
+            camera_pos=(5.5, 6.5, 3.2),
+            camera_lookat=(0.5, 1.5, 1.5),
+            camera_fov=35,
+            max_FPS=120,
+        ),
+        vis_options=gs.options.VisOptions(
+            rendered_envs_idx=[0],
+        ),
+        show_viewer=show_viewer,
+    )
+    plane = scene.add_entity(gs.morphs.Plane())
+    wheel = scene.add_entity(
+        morph=gs.morphs.URDF(
+            file="urdf/wheel/fancy_wheel.urdf",
+            pos=(0.5, 0.25, 1.6),
+            euler=(0, 0, 0),
+            fixed=True,
+            convexify=False,
+        ),
+    )
+    emitter = scene.add_emitter(
+        material=material_type(),
+        max_particles=100000,
+        surface=gs.surfaces.Glass(
+            color=(0.7, 0.85, 1.0, 0.7),
+        ),
+    )
+    scene.build(n_envs=2)
+    scene.step()