vispy flickering on Windows with real time data
ParthShah91 opened this issue · comments
I am trying to create a real time application using vispy. Basically I need to maintain a window of 1000 data at a time. So once the data that I receive crosses 1000 I will try to shift the window as well as the x-axis using 'set_range' method. This is when the flickering issues start appearing. Below is the code for the same. I am executing the code on Windows 10 and my python version is 3.12.1.
Have also attached the execution logs for your reference
realtime_execution_logs.txt
import sys
import numpy as np
from vispy import app, scene, sys_info
import random
from vispy.color.color_array import Color
print('='*80)
print(sys_info())
print('='*80)
WINDOW_SIZE = 1000
MAX_DATA_TO_PLOT = 3000
MAX_DATA_STREAMS = 8
# vertex positions of data to draw
N = WINDOW_SIZE
canvas = scene.SceneCanvas(keys='interactive', show=True)
grid = canvas.central_widget.add_grid(spacing=0)
viewbox = grid.add_view(row=0, col=1, camera='panzoom')
# add some axes
x_axis = scene.AxisWidget(orientation='bottom')
x_axis.stretch = (1, 0.1)
grid.add_widget(x_axis, row=1, col=1)
x_axis.link_view(viewbox)
y_axis = scene.AxisWidget(orientation='left')
y_axis.stretch = (0.1, 1)
grid.add_widget(y_axis, row=0, col=0)
y_axis.link_view(viewbox)
# add a line plot inside the viewbox
lines_and_data = []
for i in range(MAX_DATA_STREAMS):
data = np.empty((0, 2), dtype=np.float32)
print(data.shape)
line = scene.Line(data, color=None, parent=viewbox.scene, method='gl')
color = np.empty((0, 4), dtype=np.float32)
lines_and_data.append([line, data, color])
value_ranges = [
(10, 20, [0, 0, 1, 1]),
(25,35, [0, 1, 0, 1]),
(40, 50, [0, 1, 1, 1]),
(55,65, [1, 0, 0, 1]),
(70,80, [1, 0, 1, 1]),
(85,95, [1, 1, 0, 1]),
(100,110, [1, 1, 1, 1]),
(115,125, [0, 1, 0, 1])
]
def update(ev):
global color, line, update_call_cnt, lines_and_data
for stream_idx, el in enumerate(lines_and_data):
line, data, color = el
new_element_x = update_call_cnt
new_element_y = random.randint(value_ranges[stream_idx][0], value_ranges[stream_idx][1])
new_row = np.array([[new_element_x, new_element_y]])
data = np.vstack((data, new_row))
lines_and_data[stream_idx][1] = data.copy()
new_row = np.array(value_ranges[stream_idx][2])
color = np.vstack((color, new_row))
lines_and_data[stream_idx][2] = color.copy()
line.set_data(pos=data, color=color)
stream_idx = stream_idx + 1
update_call_cnt = update_call_cnt + 1
if update_call_cnt > WINDOW_SIZE:
viewbox.camera.set_range((update_call_cnt - WINDOW_SIZE, update_call_cnt), (0, 140))
else:
viewbox.camera.set_range((0,WINDOW_SIZE), (0,140))
return
timer = app.Timer(interval='auto', iterations=MAX_DATA_TO_PLOT)
timer.connect(update)
timer.start()
update_call_cnt = 0
if __name__ == '__main__' and sys.flags.interactive == 0:
app.run()
@djhoese Sorry to tag you directly but can you help us here?
I can take a look tomorrow most likely. I tried the code and didn't notice issues on my Mac but I have access to a Windows machine now.
Sure thank you
Okay I played around with this more. If we're seeing the same thing, this is aliasing. I can see it on my Mac if using my external (4k) monitor. I'm not sure there's much you can do to fix it easily, but maybe others have ideas.
You could start with changing the blending mode with line.set_gl_state("additive")
which for me seems to make it slightly better.
There is a vispy demo of using shaders to plot high frequency signals that might be helpful.
There are also some previous issues discussing MSAA, but unfortunately it's still not supported in vispy.
Sorry I can't be more helpful. I will come back if anything else comes to me.
Thanks for the help. I tried searching for things on my own as well.
I integrated my code into PySide6. We had data coming in at 100 ms and faced flickering issues once we started windowing. As I debugged I realised if we plot just 1 in 10 times i.e every 1 second the flickering goes away.
As I checked the examples.. ex03a_data_sources_timer, ex03b_data_sources_threaded_loop and ex03c_data_sources_threaded_events I realized that they too are being toggled at every 1 second either using time.sleep
or passing "1.0" as argument to Timer
method.
(https://github.com/vispy/vispy/tree/main/examples/scene/realtime_data)
Is this really a known constraint? Then we can convey the same to our customer and be happy with plotting data every 1 second. Maybe later you guys can fix this
I don't think it's an issue with the timer interval. It's probably just that the aliasing artifact is not as apparent with the slower update.
It's kind of hard to capture in a recording (the jump is because this is only a 3s GIF), but I see a big improvement when setting samples=16
on the Qt backend. I am using PyQt6 here.
Cool. We have a limitation that we can only use PySide6 due to licensing limitations but that's ok. Could you help us where do you set the 'samples' method/parameter in Qt backend that you mentioned? Maybe we can try something similar in PySide6 if that exists.
I don't think it's exposed in the API, but I could be wrong. I hard-coded the value here which should apply to both PySide and PyQt backends:
vispy/vispy/app/backends/_qt.py
Line 300 in 512a1ce
Ah ok will try it for my code as well. Who knows it might be a break through we need.
Hi! Sadly this still remains a problem for us. I tried changing it to 16 and of course saw some improvement but sadly it still does not match our requirements.
The configuration for our system is:
Windows version
Edition Windows 10 Home Single Language
Version 22H2
Installed on 04-03-2024
OS build 19045.4046
Experience Windows Feature Experience Pack 1000.19053.1000.0
CPU: Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz 2.90 GHz
GPU: Intel(R) HD Graphics 620 and NVIDIA GeForce 940 MX
Nvidia driver version: 545.84
Below is the output of "vispy.sys_info()": One key thing that I observe is egl is none. Is that the issue?
Platform: Windows-10-10.0.19045-SP0
Python: 3.12.1 (tags/v3.12.1:2305ca5, Dec 7 2023, 22:03:25) [MSC v.1937 64 bit (AMD64)]
NumPy: 1.26.4
Backend: PySide6
pyqt4: None
pyqt5: None
pyqt6: None
pyside: None
pyside2: None
pyside6: ('PySide6', '6.6.2', '6.6.2')
pyglet: None
glfw: None
sdl2: None
wx: None
egl: None
osmesa: None
tkinter: None
jupyter_rfb: None
_test: None
GL version: '4.6.0 NVIDIA 545.84'
MAX_TEXTURE_SIZE: 16384
Extensions: 'GL_AMD_multi_draw_indirect GL_AMD_seamless_cubemap_per_texture GL_ARB_arrays_of_arrays GL_ARB_base_instance GL_ARB_bindless_texture GL_ARB_blend_func_extended GL_ARB_buffer_storage GL_ARB_clear_buffer_object GL_ARB_clear_texture GL_ARB_clip_control GL_ARB_color_buffer_float GL_ARB_compatibility GL_ARB_compressed_texture_pixel_storage GL_ARB_conservative_depth GL_ARB_compute_shader GL_ARB_compute_variable_group_size GL_ARB_conditional_render_inverted GL_ARB_copy_buffer GL_ARB_copy_image GL_ARB_cull_distance GL_ARB_debug_output GL_ARB_depth_buffer_float GL_ARB_depth_clamp GL_ARB_depth_texture GL_ARB_derivative_control GL_ARB_direct_state_access GL_ARB_draw_buffers GL_ARB_draw_buffers_blend GL_ARB_draw_indirect GL_ARB_draw_elements_base_vertex GL_ARB_draw_instanced GL_ARB_enhanced_layouts
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