[Bug]: Why do mesh objects stick together and disappear?"

[codesbykhalil]

Bug Description

Here is my code script:

import genesis as gs
import trimesh
import os
import time
import numpy as np

def calculate_triangle_center(obj_file):
    """计算三角形的中心点位置"""
    vertices = []
    with open(obj_file, 'r') as f:
        for line in f:
            if line.startswith('v '):  # 只读取顶点行
                # 分割行并转换为浮点数
                _, x, y, z = line.split()
                vertices.append([float(x),float(z),  float(y)]) #置换y与z的坐标,将块体位置投放到xz平面，用于模拟块体坠落
                if len(vertices) == 3:  # 只需要前三个顶点
                    break
    
    if len(vertices) < 3:
        return (0, 0, 0)  # 如果没有足够的顶点，返回原点
        
    # 计算三个顶点的平均值
    vertices = np.array(vertices)
    center = np.mean(vertices, axis=0)
    return tuple(center)  # 返回(x, y, z)元组

def main():
    # 初始化Genesis
    gs.init(backend=gs.gpu,
            theme = 'light',
              precision='32'
      )  # 使用GPU后端
    
    # 创建场景，使用用户给定的参数
    scene = gs.Scene(
     sim_options=gs.options.SimOptions(substeps=8),
     show_FPS=False,
     show_viewer=True,
        # rigid_options=gs.options.RigidOptions(
        #     dt=0.01,
        #     gravity=(0,0,-0.8),
        #     enable_collision=True,
        #     constraint_solver=gs.constraint_solver.Newton,
        #     iterations=50,
        #     tolerance=1e-7,
        #     integrator=gs.integrator.implicitfast,
        #     use_contact_island=True,
        # ),
        viewer_options = gs.options.ViewerOptions(
            res           = (640, 480),  # 降低分辨率
            camera_pos    = (10, 10, 10),  # 调整相机位置到更高的位置
            camera_lookat = (5, 5, 5),  # 看向物体下落的位置
            camera_fov    = 60,  # 增加视场角以看到更多场景
            max_FPS       = 30,  # 降低帧率
        ),
        vis_options = gs.options.VisOptions(
            show_world_frame = True, # 显示原点坐标系
            world_frame_size = 5, # 坐标系长度(米)
            show_link_frame  = False, # 不显示实体链接坐标系 
            show_cameras     = False, # 不显示相机网格和视锥
            plane_reflection = False, # 开启平面反射
            ambient_light    = (0.1, 0.1, 0.1), # 环境光
           
        ),

        # renderer = gs.renderers.Rasterizer(), # 使用光栅化渲染器
    )
    # frictionless_rigid = gs.materials.Rigid(needs_coup=True, coup_friction=0.5)
   
    # 读取从prism_0.obj到prism_8.obj的文件
    temp_dir = "examples/obj/temp/temp"
    # 使用数字排序而不是字符串排序
    def get_prism_number(filename):
        # 从文件名中提取数字
        return int(filename.replace('prism_', '').replace('.obj', ''))
    
    # 获取所有obj文件并按数字排序
    obj_files = [f for f in os.listdir(temp_dir) if f.endswith('.obj')]
    obj_files = sorted(obj_files, key=get_prism_number)
    # 只保留0-8的文件
    obj_files = [f for f in obj_files if 0 <= get_prism_number(f) <= 5]
    
    print(f"将渲染以下文件: {obj_files}")
    
    E, nu = 1.e7,0.3
    rho = 100.0
    friction = 0.5
    # 保存物体引用，用于后续设置初始速度
    prism_objects = []
    
    for obj_file in obj_files:
        file_path = os.path.join(temp_dir, obj_file)
        # 计算三棱柱体积和质量（可选）
        mesh = trimesh.load(file_path)
        volume = mesh.volume
        mass = volume * 10.0  # 假设密度为10
        
        # 计算物体的中心位置
        center_pos = calculate_triangle_center(file_path)
        print(f"物体 {obj_file} 的中心位置: {center_pos}")
        
        # 添加到场景
        
        obj = scene.add_entity(
         material=gs.materials.Rigid(friction=friction),
            morph=gs.morphs.Mesh(
                file=file_path,
                scale=1,
                # pos=center_pos, 
                
            ),

            surface=gs.surfaces.Default(color=(1, 0, 0)),
        )
        prism_objects.append(obj)
     
    # 定义初始速度（只包含线性速度，3个分量）
    v_obj_init = gs.tensor([0.0, 0.0, 0, 0, 0, 0], requires_grad=True)
    # 定义阻尼参数
    damping = gs.tensor([0.0, 0.5, 0.0, 0, 0, 0])
#     obj2 = scene.add_entity(
#     gs.morphs.Box(pos=(-0.4, 0, 0.06), size=(0.1, 0.1, 0.1)),
#     surface=gs.surfaces.Default(color=(0, 0, 1)),
#     material=gs.materials.Rigid(gravity_compensation=1.0),
# )
    
   # Support
    table = scene.add_entity(
        gs.morphs.Box(pos=(0.0, 0, -10), size=(20, 20, 0.5), fixed=True),
        material=gs.materials.Rigid(friction=friction),
    )
    
    # 添加录屏相机（必须在scene.build()之前）
    cam = scene.add_camera(
        res    = (640, 480),
        pos    = (20, 0,20),
        lookat = (5, 0, 5),
        fov    = 40,
        GUI    = False,
    )

    # 构建场景
    scene.build()

    # 录屏主循环
    cam.start_recording()
    input("Start?")
    for i in range(1000):
        if i < 400:
            obj.control_dofs_velocity([2, 2, -2, 0, 0, 0])
        else:
            obj.control_dofs_velocity([0, 0, 0, 0, 0, 0])
            scene.step()
            cam.render()
    cam.stop_recording(save_to_filename='examples/obj/prism_simulation.mp4', fps=30)
    print('录屏已结束，视频已保存。')

    # 继续交互式运行（可选）
    while True:
        scene.step()

if __name__ == "__main__":
    main() 

Steps to Reproduce

Here is my obj files

temp.zip

Expected Behavior

Looking forward to your response.

Release version or Commit ID

first

[duburcqa]

The issue is not clear for now. Could you share a video?

[codesbykhalil]

https://github.com/user-attachments/assets/0d937290-4aad-4370-a84b-6c3ede6bf0c3 Hello.From this video, you can see that at the beginning of the scene, objects suddenly disappear, making further simulation impossible. I think the possible reasons are: 1) shared vertices between models, and 2) a minimum size limitation for blocks. I'm not entirely sure if Genesis has limitations in this regard, and I hope to get a response from the developers. Thank you.