spice plot is stepped

[Thomas Pointhuber]

# HowTo Reproduce

1. draw simple voltage divider
2. simulate with DC Source, 0V-10V, 100m voltage steps
3. see that no interpolation takes place in the graph

# Expected behavior

interpolate results at least in a linear way

# Version Information

Application: kicad
Version: (6.0.0-rc1-dev-1447-gdeae6d5bb), debug build
Libraries:
    wxWidgets 3.1.1
    libcurl/7.63.0 OpenSSL/1.1.1a zlib/1.2.11 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.4) libssh2/1.8.0 nghttp2/1.35.1
Platform: Linux 4.19.12-arch1-1-ARCH x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.1.1 (wchar_t,wx containers) GTK+ 3.24
    Boost: 1.68.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.62.0
    Compiler: Clang 7.0.1 with C++ ABI 1002

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[NhatKhai (nhatkhai)]

I think it look as expected. Can you check ngspice manual?

[Nick Østergaard (nickoe)]

Maybe it is a regression in how stuff is plotted.

Looking at the old video from https://youtu.be/A2_-hdRcf4U?t=208

And running the demo locally, the plots look very different. In the video the lines are not stepped, and the No. of Data Rows : 61 are the same...

[Holger Vogt (h+vogt)]

May I ask you to raise the severity of this bug?

In my view this bug completely discredits the eeschema-ngspice interface.

Any user coming from another simulator (or plain ngspice) would immediately stumble over the ugly looking plot.

The bug probably has nothing to do with interpolation, but in contrast to 5.0.2 release, the 5.1.0 release and current nigtly seems to wronly connect two consecutive points in the graph not by a straight line, but by firstly doing a delta-x and then a delta-y.

Application: eeschema
Version: (5.1.0-41-ga7c8df566), release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.61.1 OpenSSL/1.1.1 (WinSSL) zlib/1.2.11 brotli/1.0.6 libidn2/2.0.5 libpsl/0.20.2 (+libidn2/2.0.5) nghttp2/1.34.0
Platform: Windows 7 (build 7601, Service Pack 1), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8)
    Boost: 1.68.0
    OpenCASCADE Community Edition: 6.9.1
    Curl: 7.61.1
    Compiler: GCC 8.2.0 with C++ ABI 1013

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=OFF
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_USE_OCC=OFF
    KICAD_SPICE=ON

[Seth Hillbrand (sethh)]

You are right. We shouldn't be releasing regressions like this.

[KiCad Janitor (kicad-janitor)]

Fixed in revision c1c4a0925d04144fc895ddc2a42ebbd165c4a9e1
https://git.launchpad.net/kicad/patch/?id=c1c4a0925d04144fc895ddc2a42ebbd165c4a9e1