Forge elements missing in some direction

My model is a pipe line and this is the screenshot from IFC viewer

and this is the screenshot from forge viewer

You can see in the forge I can't see the full pipe line. When I zoom in or change the direction some parts will missing. It only happens when close to model.

This seems to be one of the pathological cases where, due to the extremely large extent of the 3D design, the viewer heuristic (which tries to optimize the near/far clipping planes to avoid precision issues) fails. What's the bounding box of your model (you can retrieve it using viewer.model.getBoundingBox())?

To work around this, you could try the following:

• switch the camera from perspective mode to orthogonal
• set the near radius to 1 (viewer.impl.setNearRadius(1)) as suggested in this Stack Overflow discussion: Autodesk Forge Viewer - Near and Far clipping issues