I’ve just redone my code signatures today.

One of the habits which I have in my life is, first to undertake a programming project, then to make sure it works, and finally to post some of it on my blog, where I can tell people ‘what I did, to make the project work’. As a result, some of my postings point to a ‘binaries page’, which has the following URL:

https://dirkmittler.homeip.net/binaries/

What gets shown is a table of contents, from which it’s virtually impossible to intuit what each compressed file is actually about. However, individual posts which link there, usually state, which compressed file resulted from the exercise.

Later, I got the idea to compile some of those projects, on behalf of readers who may not know how to do so, AND, to compile a subset again, to run under Windows.

What makes this tricky is the fact that, under Windows, people like me are obliged to put code signatures onto executables. My code signature only identifies me positively, as the author of the program. It doesn’t, by itself, guarantee, that the user won’t get the scary Windows defender message, when he or she double-clicks on the file-icon.

What makes this even tricker with the type of certificate I chose (to use, to sign the .EXE Files), is, that each certificate expires after one year. Even if readers did download the bundles before yesterday (May 12, 2021), the code would absolutely refuse to work, after May 25 this year. Thus, I need to buy a new certificate, and anybody who might want to keep using my programs, also needs to re-download them.

As of today, I have re-signed all the .EXE Files, with a newer certificate, which will ‘only’ expire after May 13, 2022. So, my readers may proceed, if they have used my program(s), and wish to continue doing so.

(Update 5/14/2021, 14h30: )

Just to be exact, the certificate which I actually used, has the Serial Number ‘154a757a67e7fd31188adce1474afadc‘.

Dirk

A simple 3D animation created with Maxima.

One of the things which I find myself doing quite often is, to be undertaking some sort of task on the computer(s), that I know is possible, but, not knowing in advance what the correct syntax and semantics are, to perform this task. This tends to take me on some sort of search on the Web, and I’ll find that other people have undertaken similar tasks, but not, a task with the same combination of parameters, as my task.

Thus, Web pages can be found according to which 2D animations have been created using a free, open-source Computer Algebra System named “Maxima”. Other Web pages may explain how to create various types of (static) 3D plots. But there may just be lacking examples out there, on how to create the 3D plot, but to animate it.

Using Maxima, there may be more than one way, such as, to keep refreshing the 3D plot over a time interval. But I find that such solutions tend to be second-rate, because of their use of busy-wait loops, as well as the possibility that they may otherwise be wasteful of computing power. I think that the best way, perhaps, to get Maxima to generate an animated 3D plot, could be, in the form of an animated GIF File (of course, as long as there isn’t an excess of frames to this animation).

Thus, the recipe that seems to work is as such:


load(draw)$scenes: []$

for i thru 20 do (
scenes: append(scenes,
[gr3d(explicit(sin(%pi*(x+(i/10)))*cos(%pi*y),
x, -1, 1, y, -1, 1))]
)
)$draw( delay = 10, file_name = "wavy", terminal = 'animated_gif, scenes )$



The script outputs a file named ‘wavy.gif’ in the same folder, as whatever folder it was originally stored in. In some cases, the GIF File may appear in the user’s home directory, or even, in a temporary directory that’s difficult to find, unless the user also gives a full-path name for the file.

And, this is the GIF File that results:

Caution:

My most recent posting had to do, with a version of Maxima that had been ported to Android. The example above will not work with that version of Maxima. In fact, I can really only be sure that this feature works under Linux, which is the O/S that Maxima was mainly designed to run on. Any directives to ‘plot()’ or ‘draw()’ open a separate GNU-Plot window, which behaves in the predictable way under Linux, including the user’s ability to rotate the 3D plots interactively. AFAIK, commands to change to a non-default ‘terminal’ (for drawing and/or plotting) will fail on other platforms.

But, There is also a Windows or Mac alternative to using this platform, which mainly presents itself in the application ‘wxMaxima’. Here, the functions ‘wxdraw2d()’ and ‘wxdraw3d()’ replace those that open a separate window, and both embed their results in the wxMaxima worksheet. In order to make this more versatile, wxMaxima also offers the functions ‘with_slider_draw()’, ‘with_slider_draw3d()’, ‘wxanimate_draw()’, and ‘wxanimate_draw3d()’.

Potential ‘wxMaxima’ users will find the documentation for how to script that Here.

(Updated 7/06/2020, 15h35… )

A bit of my personal history, experimenting in 3D game design.

I was wide-eyed and curious. And much before the year 2000, I only owned Windows-based computers, purchased most of my software for money, and also purchased a license of 3D Game Studio, some version of which is still being sold today. The version that I purchased well before 2000 was using the ‘A4′ game engine, where all the 3DGS versions have a game engine specified by the latter ‘A’ and a number.

That version of 3DGS was based on DirectX 7 because Microsoft owns and uses DirectX, and DirectX 7 still had as one of its capabilities to switch back into software-mode, even though it was perhaps one of the earliest APIs that offered hardware-rendering, provided that is, that the host machine had a graphics card capable of hardware-rendering.

I created a simplistic game using that engine, which had no real title, but which I simply referred to as my ‘Defeat The Guard Game’. And in so doing I learned a lot.

The API which is referred to as OpenGL, offers what DirectX versions offer. But because Microsoft has the primary say in how the graphics hardware is to be designed, OpenGL versions are frequently just catching up to what the latest DirectX versions have to offer. There is a loose correspondence in version numbers.

Shortly after the year 2000, I upgraded to a 3D Game Studio version with their ‘A6′ game engine. This was a game engine based on DirectX 9.0c, which was also standard with Windows XP, which no longer offered any possibility of software rendering, but which gave the customers of this software product their first opportunity to program shaders. And because I was playing with the ‘A6′ game engine for a long time, in addition owning a PC that ran Windows XP for a long time, the capabilities of DirectX 9.0c became etched in my mind. However, as fate would have it, I never actually created anything significant with this game engine version – only snippets of code designed to test various capabilities.

One of the facts about modern computing is, that the hardware could include a multi-core CPU, with a number of virtual cores different from the number of full cores. Such CPUs were once called “Hyper-Threaded”, but are now only called “Threaded”.

If the CPU has 8 virtual cores, but is threaded as only 4 full cores, then there will only be a speed advantage, when running 4 processes. But because processes are sometimes multi-threaded, each of those 4 processes could consist of 2 fully-busy threads, and benefit from a further doubling of speed because each full core has 2 virtual cores.

It’s really a feature of Windows to exploit this fully, while Linux tends to ignore this. When Linux runs on such a CPU, it only ‘sees’ the maximum number of virtual cores, as the logical number of cores that the hardware has, without taking into account that they could be pairing in some way, to result in a lower number of full cores.

And to a certain extent, the Linux kernel is justified in doing so because unlike how it is with Windows, it’s actually just as cheap for a Linux computer to run a high number of separate processes, as it is to run processes with the same number of threads. Two threads share a code segment as well as a data segment (heap), but have two separate stack segments as well as different register-values. This makes them ‘enlightened processes’. Well they only really run faster under Windows (or maybe under OS/X).

Under Linux it’s fully feasible just to create many processes instead, so the bulk of the programming work does not make use as much of multi-threading. Of course Even under Linux, code is sometimes written to be multi-threaded, for reasons I won’t go into here.

But then under Linux, there was also never effort put into the kernel recognizing two of its logical cores, as belonging to the same full core.

(Updated 2/19/2019, 17h30 … )