Implement rendering capability for FSI-SPH in Chrono::Sensor (#738)

* Add CRM rendering capability

* Add CRM rendering capability

* Add assets for sprite rendering

* Use a separate demo for CRM Rendering

* Render FSI-SPH system natively on GPU

* Removed unused functions

* Implement the visual_spacing, remove unused assets

* Rename demo_ROBOT_Viper_CRM_Wheelsinkage to demo_SEN_CRM_Rendering

* Relocate particles for CRM Rendering demo

* clang-format

* Update mesh name prefix for regolith models

Author: uebian

data/models/regolith/generate_regolith.py

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+import bpy
+import random
+import os
+
+# Directory where the OBJ files will be saved
+export_directory = "/tmp/regolith/"  # Change this to your desired path
+
+def create_granular_particle():
+    # Create a base shape (e.g., icosphere for a round particle)
+    bpy.ops.mesh.primitive_ico_sphere_add(subdivisions=2, radius=0.5, location=(0, 0, 0))  # Generate at origin
+    particle = bpy.context.object
+
+    # First Displace Modifier for Coarse Roughness
+    bpy.ops.object.modifier_add(type='DISPLACE')
+    displace_mod = particle.modifiers[-1]
+
+    # Create a texture for coarse displacement
+    tex_name = "CoarseRoughTexture_" + str(random.randint(0, 10000))
+    tex = bpy.data.textures.new(name=tex_name, type='VORONOI')
+    tex.noise_intensity = random.uniform(0.8, 1.2)
+    tex.distance_metric = 'MINKOVSKY'
+    tex.minkovsky_exponent = random.uniform(0.6, 0.9)
+
+    displace_mod.texture = tex
+    displace_mod.strength = random.uniform(0.1, 0.3)
+
+    bpy.ops.object.modifier_apply(modifier=displace_mod.name)
+
+    # Second Displace Modifier for Fine Surface Detail
+    bpy.ops.object.modifier_add(type='DISPLACE')
+    displace_mod2 = particle.modifiers[-1]
+    tex_name2 = "FineRoughTexture_" + str(random.randint(0, 10000))
+    tex2 = bpy.data.textures.new(name=tex_name2, type='CLOUDS')
+    tex2.noise_scale = random.uniform(0.1, 0.15)
+    displace_mod2.texture = tex2
+    displace_mod2.strength = random.uniform(0.02, 0.08)
+
+    bpy.ops.object.modifier_apply(modifier=displace_mod2.name)
+
+    # Subdivision Surface Modifier for smoothing
+    bpy.ops.object.modifier_add(type='SUBSURF')
+    subsurf_mod = particle.modifiers[-1]
+    subsurf_mod.levels = 1
+    bpy.ops.object.modifier_apply(modifier=subsurf_mod.name)
+
+    # Random rotation for variety
+    particle.rotation_euler = (random.uniform(0, 360), random.uniform(0, 360), random.uniform(0, 360))
+
+    # Randomize the shape: flat, elongated, or round
+    shape_variation = random.choice(['round', 'flat', 'elongated'])
+
+    if shape_variation == 'flat':
+        particle.scale = (random.uniform(0.008, 0.012),
+                          random.uniform(0.008, 0.012),
+                          random.uniform(0.004, 0.006))
+    elif shape_variation == 'elongated':
+        elongation_axis = random.choice(['x', 'y', 'z'])
+        if elongation_axis == 'x':
+            particle.scale = (random.uniform(0.015, 0.02),
+                              random.uniform(0.008, 0.012),
+                              random.uniform(0.008, 0.012))
+        elif elongation_axis == 'y':
+            particle.scale = (random.uniform(0.008, 0.012),
+                              random.uniform(0.015, 0.02),
+                              random.uniform(0.008, 0.012))
+        elif elongation_axis == 'z':
+            particle.scale = (random.uniform(0.008, 0.012),
+                              random.uniform(0.008, 0.012),
+                              random.uniform(0.015, 0.02))
+    else:
+        particle.scale = (random.uniform(0.008, 0.012),
+                          random.uniform(0.008, 0.012),
+                          random.uniform(0.008, 0.012))
+
+    # Create a new material for lunar regolith appearance
+    mat = bpy.data.materials.new(name="LunarRegolithMaterial")
+    mat.use_nodes = True
+    nodes = mat.node_tree.nodes
+    links = mat.node_tree.links
+
+    # Clear default nodes
+    for node in nodes:
+        nodes.remove(node)
+
+    # Add necessary nodes
+    output_node = nodes.new(type='ShaderNodeOutputMaterial')
+    principled_bsdf = nodes.new(type='ShaderNodeBsdfPrincipled')
+
+    # Set base color to dark gray (lunar regolith color)
+    principled_bsdf.inputs['Base Color'].default_value = (0.3, 0.3, 0.3, 1.0)
+
+    # Increase roughness for a dusty look
+    principled_bsdf.inputs['Roughness'].default_value = 0.9
+
+    # Add noise texture for bump mapping (surface roughness)
+    noise_texture = nodes.new(type='ShaderNodeTexNoise')
+    noise_texture.inputs['Scale'].default_value = 30.0
+    noise_texture.inputs['Detail'].default_value = 2.0
+
+    # Add bump node to connect noise texture for surface detail
+    bump_node = nodes.new(type='ShaderNodeBump')
+    bump_node.inputs['Strength'].default_value = 0.3  # Moderate bump effect
+
+    # Connect noise texture to bump node
+    links.new(noise_texture.outputs['Fac'], bump_node.inputs['Height'])
+
+    # Connect bump node to Principled BSDF normal input
+    links.new(bump_node.outputs['Normal'], principled_bsdf.inputs['Normal'])
+
+    # Connect BSDF to Material Output
+    links.new(principled_bsdf.outputs['BSDF'], output_node.inputs['Surface'])
+
+    # Assign the material to the particle
+    particle.data.materials.append(mat)
+
+    return particle, mat
+
+def export_particle_as_obj(particle, file_name):
+    # Select the particle before exporting
+    bpy.ops.object.select_all(action='DESELECT')  # Deselect all
+    particle.select_set(True)  # Select the particle to export
+
+    # Export the particle as an OBJ file with the material
+    bpy.ops.wm.obj_export(filepath=file_name, export_selected_objects=True, export_materials=True)
+
+def delete_particle_and_material(particle, material):
+    # Delete the particle and its material
+    bpy.data.objects.remove(particle, do_unlink=True)
+    bpy.data.materials.remove(material, do_unlink=True)
+
+# Number of granular particles to generate and export
+num_particles = 10
+
+for i in range(num_particles):
+    # Step 1: Generate a particle
+    particle, material = create_granular_particle()
+
+    # Step 2: Export the particle as OBJ with the material
+    obj_file_name = os.path.join(export_directory, f"particle_{i+1}.obj")
+    export_particle_as_obj(particle, obj_file_name)
+
+    # Step 3: Delete the particle and material
+    delete_particle_and_material(particle, material)
+
+    print(f"Particle {i+1} exported and deleted.")
+

data/models/regolith/particle_1.mtl

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+# Blender 4.2.1 LTS MTL File: 'lunarregolith.blend'
+# www.blender.org
+
+newmtl LunarRegolithMaterial.032
+Ns 10.000005
+Ka 1.000000 1.000000 1.000000
+Kd 0.500000 0.500000 0.500000
+Ks 0.500000 0.500000 0.500000
+Ke 0.000000 0.000000 0.000000
+Ni 1.500000
+d 1.000000
+illum 2