"[optic_flow_viz-3] process has died" when running basic test

[mohammed-amr]

Setup:

• Using a conda environment with Python 2.7.13
• gcc 5.5
• Ubuntu 18.04
• ROS Melodic

Problem: Getting [optic_flow_viz-3] process has died when running the basic Planar Renderer test: roslaunch esim_ros esim.launch config:=cfg/example.conf

The process ends and prints frames, but no visualization is shown when I run the visualization process, just an empty space in rviz:

Abridged output:

... logging to /home/mosayed/.ros/log/a9d04b40-58c4-11ea-9ff4-305a3a5b85cd/roslaunch-eddie-30746.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://eddie:34607/

SUMMARY
========

PARAMETERS
 * /optic_flow_viz/arrows_scale: 0.07
 * /optic_flow_viz/arrows_step: 7
 * /optic_flow_viz/arrows_upsample_factor: 1
 * /optic_flow_viz/publish_rate: 100
 * /rosdistro: melodic
 * /rosversion: 1.14.3

NODES
  /
    dvs_renderer (dvs_renderer/dvs_renderer)
    esim_node (esim_ros/esim_node)
    optic_flow_viz (esim_visualization/optic_flow_converter.py)

ROS_MASTER_URI=http://localhost:11311

process[esim_node-1]: started with pid [30761]
process[dvs_renderer-2]: started with pid [30762]
process[optic_flow_viz-3]: started with pid [30763]
I0226 18:40:47.584417 30761 imu_factory.cpp:20] Initialize bias ...
I0226 18:40:47.598414 30761 imu_factory.cpp:27] done.
I0226 18:40:47.598429 30761 imu_factory.cpp:35] Initialize IMU ...
I0226 18:40:47.598433 30761 imu_factory.cpp:44] done.
I0226 18:40:47.598946 30761 data_provider_online_render.cpp:63] Horizontal FOV: 61.7164 deg
I0226 18:40:47.598968 30761 data_provider_online_render.cpp:64] Vertical FOV: 48.2168 deg
I0226 18:40:47.598974 30761 data_provider_online_render.cpp:65] Diagonal FOV: 73.4823 deg
I0226 18:40:47.598981 30761 renderer_factory.cpp:75] Loading texture file from file: /home/mosayed/sim_ws/src/rpg_esim/event_camera_simulator/imp/imp_planar_renderer/textures/office.jpg.
I0226 18:40:47.653774 30761 renderer_factory.cpp:85] Pre-filtering the texture with median filter of size: 13.
[INFO] [1582742447.715853]: Started flow converter node
[INFO] [1582742447.717069]: Step size between arrows: 7
[INFO] [1582742447.718602]: Scale factor: 0.07
[INFO] [1582742447.719399]: Upsample factor: x1
[INFO] [1582742447.720216]: Publish rate: 100 Hz
I0226 18:40:48.083510 30761 renderer_factory.cpp:92] Pre-filtering the texture with gaussian filter of size: 2.
I0226 18:40:48.178323 30761 planar_renderer.cpp:34] K_src = 2269.92 0000000 0002080
0000000 2269.92 0001560
0000000 0000000 0000001
I0226 18:40:48.178382 30761 planar_renderer.cpp:36] T_W_P = 01 00 00 00
00 -1 00 00
00 00 -1 -1
00 00 00 01
I0226 18:40:48.185529 30761 ros_publisher.cpp:37] Initializing ROS
I0226 18:40:48.286394 30761 rosbag_writer.cpp:39] Will write to bag: /tmp/out.bag
W0226 18:40:48.286417 30761 adaptive_sampling_benchmark_publisher.cpp:57] Empty benchmark folder string: will not write benchmark files
W0226 18:40:48.286589 30761 synthetic_optic_flow_publisher.cpp:41] Empty output folder string: will not write synthetic optic flow files
I0226 18:40:48.286903 30761 rosbag_writer.cpp:275] t = 0.001 s
I0226 18:40:48.291484 30761 event_simulator.cpp:27] Converting the image to log image with eps = 0.001.
I0226 18:40:48.291757 30761 event_simulator.cpp:11] Initialized event camera simulator with sensor size: [240 x 180]
I0226 18:40:48.291774 30761 event_simulator.cpp:12] and contrast thresholds: C+ = 0.5 , C- = 0.5
W0226 18:40:48.291919 30761 camera_simulator.cpp:43] The images do not cover a time span long enough to simulate the exposure time accurately.
[optic_flow_viz-3] process has died [pid 30763, exit code -11, cmd /home/mosayed/sim_ws/src/rpg_esim/event_camera_simulator/esim_visualization/src/py/optic_flow_converter.py flow:=/cam0/optic_flow __name:=optic_flow_viz __log:=/home/mosayed/.ros/log/a9d04b40-58c4-11ea-9ff4-305a3a5b85cd/optic_flow_viz-3.log].
log file: /home/mosayed/.ros/log/a9d04b40-58c4-11ea-9ff4-305a3a5b85cd/optic_flow_viz-3*.log
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
I0226 18:40:48.803850 30761 rosbag_writer.cpp:275] t = 0.501 s

...

I0226 18:41:39.413239 30761 rosbag_writer.cpp:275] t = 99.501 s
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
publish image from callback
I0226 18:41:39.953985 30761 rosbag_writer.cpp:62] Finalizing the bag...
I0226 18:41:40.698477 30761 rosbag_writer.cpp:64] Finished writing to bag: /tmp/out.bag
[esim_node-1] process has finished cleanly

Note: Abnormal things I had to do: the matplotlib module failed to compile unless I removed -Werror on warnings in the associated make file.

Any help is appreciated. Thank you.