Making fisheye camera model for Gazebo sim.

Modeled Intel Realsense T265
Referred Fisheye Lense model and this Link

Result video clip

in the .sdf file, insert camera sensor with wideanglecamera type.
Circular fisheye lense model with Stereographic mapping function are used.
cutoff_angle is assumed as 163 degree, according to T265’s datasheet.

  <sensor name="camera" type="wideanglecamera">
    <camera name="left">
      <pose>0 0 0 0 0 0</pose>
      <horizontal_fov>3.141592</horizontal_fov>
      <image>
        <width>848</width>
        <height>800</height>
        <format>R8G8B8</format>
      </image>
      <clip>
        <near>0.15</near>
        <far>1500</far>
      </clip>
      <noise>
        <type>gaussian</type>
        <mean>0.0</mean>
        <stddev>0.0001</stddev>
      </noise>
      <lens>
        <type>custom</type> 
        <custom_function> <!-- manually defined mapping function r = c1*f*fun(theta/c2 + c3) More information here: https://en.wikipedia.org/wiki/Fisheye_lens#Mapping_function -->
          <c1>1.0</c1>    <!-- linear scaling -->
          <c2>1.95</c2>       <!-- angle scaling -->
          <f>6</f>       <!-- one more scaling parameter -->
          <fun>tan</fun>   <!-- one of sin,tan,id -->
        </custom_function>
        <scale_to_hfov>true</scale_to_hfov>  <!-- if it is set to `true` your horizontal FOV will ramain as defined, othervise it depends on lens type and custom function, if there is one -->
        <!-- clip everything that is outside of this angle -->
        <cutoff_angle>2.84488668</cutoff_angle>
        <env_texture_size>512</env_texture_size> <!-- resolution of the cubemap texture, the highter it is - the sharper is your image -->
      </lens>
      <always_on>1</always_on>
      <update_rate>30</update_rate>
    </camera>
    <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
      <robotNamespace>/t265</robotNamespace>
      <cameraName>stereo_ir/left</cameraName>
      <imageTopicName>fisheye_image_raw</imageTopicName>
      <cameraInfoTopicName>camera_info</cameraInfoTopicName>
      <frameName>camera_link</frameName>
      <hackBaseline>0</hackBaseline>
    </plugin>
  </sensor>