ipkiss 3.12版加入write_obj函数，可以直接输出器件的三维模型。

如，输出自定义的mmi的三维模型：

代码如下：

from si_fab import all as pdk
from ipkiss3 import all as i3


class MMI1x2(i3.PCell):
    """MMI with 1 input and 2 outputs."""

    _name_prefix = "MMI1x2"
    trace_template = i3.TraceTemplateProperty(doc="Trace template of the access waveguide")
    width = i3.PositiveNumberProperty(default=4.0, doc="Width of the MMI section.")
    length = i3.PositiveNumberProperty(default=20.0, doc="Length of the MMI secion.")
    taper_width = i3.PositiveNumberProperty(default=1.0, doc="Width of the taper.")
    taper_length = i3.PositiveNumberProperty(default=5.0, doc="Length of the taper")
    waveguide_spacing = i3.PositiveNumberProperty(default=2.0, doc="Spacing between the waveguides.")

    def _default_trace_template(self):
        return pdk.SiWireWaveguideTemplate()

    class Layout(i3.LayoutView):
        def _generate_elements(self, elems):
            length = self.length
            width = self.width
            taper_length = self.taper_length
            taper_width = self.taper_width
            half_waveguide_spacing = 0.5 * self.waveguide_spacing
            core_layer = self.trace_template.core_layer
            cladding_layer = self.trace_template.cladding_layer
            core_width = self.trace_template.core_width

            # Si core
            elems += i3.Rectangle(
                layer=core_layer,
                center=(0.5 * length, 0.0),
                box_size=(length, width),
            )
            elems += i3.Wedge(
                layer=core_layer,
                begin_coord=(-taper_length, 0.0),
                end_coord=(0.0, 0.0),
                begin_width=core_width,
                end_width=taper_width,
            )
            elems += i3.Wedge(
                layer=core_layer,
                begin_coord=(length, half_waveguide_spacing),
                end_coord=(length + taper_length, half_waveguide_spacing),
                begin_width=taper_width,
                end_width=core_width,
            )
            elems += i3.Wedge(
                layer=core_layer,
                begin_coord=(length, -half_waveguide_spacing),
                end_coord=(length + taper_length, -half_waveguide_spacing),
                begin_width=taper_width,
                end_width=core_width,
            )

            # Cladding
            elems += i3.Rectangle(
                layer=cladding_layer,
                center=(0.5 * length, 0.0),
                box_size=(length + 2 * taper_length, width + 2.0),
            )
            return elems

        def _generate_ports(self, ports):
            length = self.length
            taper_length = self.taper_length
            trace_template = self.trace_template
            half_waveguide_spacing = 0.5 * self.waveguide_spacing

            ports += i3.OpticalPort(
                name="in1",
                position=(-taper_length, 0.0),
                angle=180.0,
                trace_template=trace_template,
            )
            ports += i3.OpticalPort(
                name="out1",
                position=(length + taper_length, -half_waveguide_spacing),
                angle=0.0,
                trace_template=trace_template,
            )
            ports += i3.OpticalPort(
                name="out2",
                position=(length + taper_length, half_waveguide_spacing),
                angle=0.0,
                trace_template=trace_template,
            )
            return ports

    class Netlist(i3.NetlistFromLayout):
        pass


if __name__ == '__main__':
    mmi_layout = MMI1x2().Layout()
    mmi_layout.visualize(annotate=True)

    mmi_geometry = i3.device_sim.SimulationGeometry(
        layout=mmi_layout,
        process_flow=i3.TECH.VFABRICATION.PROCESS_FLOW,
    )
    mmi_geometry.write_obj(filename="mmi.obj")

输出三维模型部分的代码：

mmi_geometry = i3.device_sim.SimulationGeometry(
        layout=mmi_layout,
        process_flow=i3.TECH.VFABRICATION.PROCESS_FLOW,
    )
    mmi_geometry.write_obj(filename="mmi.obj")

生成的obj文件可以用Mayo打开。