## OGRE 1.10 and Geometry Shader Support

On my Debian / Jessie laptop ‘Klystron’, I gave up some time ago, in compiling OGRE 1.10, this just resulting in a mess. Instead, on that platform I was only able to build OGRE 1.9 from source code, which is fully stable, as long as we stick to the OpenGL (2) Render System.

On the Windows 7 desktop ‘Mithral’, my first attempt to build OGRE 1.10 also failed, resulting in a successful compile, but then a silent crash of the Sample Browser, indicating that something was not built right.

If I have OGRE installed on several machines, it makes most sense for them to be the same OGRE version, so next I compiled OGRE 1.9 on ‘Mithral’, successfully, using Visual Studio 2015.

In response to my observation, that I had not set up the dependencies correctly on the ‘Mithral’ build attempt of OGRE 1.10, I now re-attempted that, paying closer attention to all the details, specified within CMake 3.6.2 .

I found that I could not only build OGRE 1.10 on this machine but also run it. And I found, that contrarily to how it was with OGRE 1.9, the OpenGL3+ Render System of OGRE 1.10 is capable of producing working Geometry Shaders. At least this gives me some access to Geometry Shaders, and casts doubt back onto the MESA Drivers of ‘Klystron’, which would cause the X-Server to crash, if I ran the Geometry Shader example of OGRE 1.10 .

What I still cannot do, is build the DirectX 11 Render System that is supposed to work under OGRE 1.10 , due to errors I have not yet pinned down. But what that was supposed to bring me, is now being provided successfully by the OpenGL3+ Render System. Both of these two are stated by the OGRE Team, to be experimental render systems, for version 1.10 still.

I suspect that OGRE 1.10 is being neglected by their team, in favor of OGRE 2.1, which is their effort to port OGRE to Android.

Dirk

## I have been test-driving Visual Studio Express 2015.

One of the projects which I attempted today on the Windows 7 desktop computer I name ‘Mithral’, was to compile OGRE 1.10 . This is an unstable build of OGRE, and it would be helpful for me to know whether this instability comes more, from the software, or from the weaker graphics card on my Linux laptop ‘Klystron’, which I have already had to switch to OGRE 1.9 .

My initial attempt to compile OGRE 1.10 failed in a foreboding way: The rendering window would open, and then be black for a second, and then give way to the nondescript Windows Error box, telling me that the program had crashed. There were no traces of error messages in the log to explain why. This is called “a silent crash”. Hypothetically, it could point to a borked compiler setup.

So what I did next was to download an OGRE 1.9 SDK, which had been entirely pre-compiled by OGRE devs. But then I knew this had been a waste of time, because it nowhere proves that my compiler can actually compile. And yes, that SDK was unstable on my stronger graphics card.

I have come to learn something. Even having a Microsoft compiler does not guarantee that I will be able to compile a DirectX rendering engine. The main reason for this, is the fact that DirectX 9 is almost deprecated. The up-to-date Microsoft SDK no longer includes libraries and header files, which legacy DirectX applications linked against – including OGRE. This means that the OGRE SDK can offer DirectX 11 support, not Dx 9, and its DirectX 11 support is unstable out-of-the-box. This is ultimately a fault of the software.

What I did next was to compile OGRE 1.9 . When I was setting up the CMake parameters to do so, I realized that when I had been setting up CMake for 1.10 , I had made mistakes that could have led to severe code-linking issues. Specifically, under Windows, it is tedious how we need to link to each core-dependency one-by-one. Under Linux or MinGW these can all get picked up in an automated batch. But with MSVC, it is not so easy.

Compiling OGRE 1.9 with the OpenGL2 and the OpenGL3+ rendering engines was a success, and so finally proved that my new compiler can produce moving, 3D images. Unfortunately though, 1.9 was code that still used the deprecated way of linking to the Windows SDK for Dx 9 and 11 , so that I could not build the DirectX 11 engine after all.

I found that just with OGRE 1.9.0 , and OpenGL2, I was able to get a larger set of animations to run, from the Sample Browser, than I was on my laptop. This proves, that much of the trouble I was having with ‘Klystron’, or before that, ‘Maverick’, were in fact hardware issues.

The Iso-Surface Demo works along a different principle than I had anticipated. It is one of those applications, which use a Fragment Shader, which renders to a Vertex Buffer, set up to look like a Pixel Buffer. The Pixel format output has been cleverly engineered also to correspond to a vertex attribute structure, thus achieving what was once known as ‘a poor mans Geometry Shader’.

The Iso-Surface Demo is supposed to work, even with the OpenGL2 rendering engine. Only, on my laptop, there is no support for Render To Vertex Buffer, aka ‘R2VB’.

With OGRE 1.9 , the OpenGL3+ rendering engine remains unstable as heck, unusable.

There is an issue with how VS 2015 ultimately works. Since ‘Mithral’ possesses 8 cores, threaded as 4, VS will ultimately try to build up to 8 targets at once. This pushes performance to the max, but at the expense of stability. Today I was pushing this compiler for hours and hours – and I later learned that it truly maxes out all 8 cores.

I found a setting to correct this for the future. Given 8 cores, I would like a maximum of 6 compile targets worked on concurrently. This is just, so that the system will have a full CPU left, to work on other tasks, should things go wonky. Because by the end of the day, things did go wonky – for whatever reason.

Dirk

(Edit 09/16/2016 : ) Another disadvantage, If we have an 8-core CPU, and If our compiler wants to build 8 targets concurrently for that reason, is the fact that 1 source file being compiled at a time, for each target, can consume an unpredictable amount of RAM. If the amount of RAM on the system is not taken into consideration, an ‘OOM’ (‘Out Of Memory’) condition can arise, because of the arbitrary 8 jobs running at once.

And I think that last night, such an OOM condition did arise, because I was installing tons of software… I have 8GB of RAM on ‘Mithral’. I performed numerous defragmentations as well, and, because many programs do have memory leaks, everything last night may have led up to an OOM condition by the end of the day.

I also installed Boost 1.61, and Boost 1.59, where before I only had Boost 1.47. And Boost 1.61 may in fact be necessary for OGRE 1.10 to compile, as another reason why my first attempt to compile that had failed.

## This Time, some Real Computer Achievement

Contrarily to how easy it was to set up my Joystick the other day, yesterday and today I have been busy with the laptop I name ‘Klystron’ that actually required some computer-skills on my part.

It was a subject of mine for a long time, how 3D Game Design works, and in particular, how the raster-based DirectX or OpenGL rendering works. To study that subject in my private time, I have always maintained a set of programs, that would in theory enable me to create a game.

In practice, creating any game decent enough to play, requires oodles of time and work. But I always felt that the software-tools involved should belong to my collection, even if I do not really put them to thorough use.

One software tools I have been pursuing, is the graphics rendering engine called “OGRE“. For several years I have been trying to custom-compile OGRE 1.10, just because that version offers better support for OpenGL 3, which should give game authors access to Geometry Shaders. But as it happens, I have ‘Mesa‘ drivers installed on that laptop, that do claim to create support for OpenGL 3, but that oddly, do not go so far as to offer Geometry Shaders. This is not a fault of the OGRE development team.

Also, there are reasons for which I do not simply ditch the Mesa drivers for ‘fglrx‘, the latter of which would give me OpenGL 4: I find it important enough, that the Mesa drivers allow hardware-acceleration of regular, high-def, 2D video streams. I would not want a real video stream / movie to become a burden to my CPU, and the fglrx do not GPU-accelerate that. So I stick with the Mesa drivers.

But then there was only one good way to get my OGRE install stable. I had to switch the Mercurial version of it I was subscribing to, down to OGRE 1.9, which is highly stable. The only issue with that remains, that OGRE 1.10 would have been my only game engine, which would have ever offered me full OpenGL 3. Which was just not stable on that box.

Now that the OGRE version on ‘Klystron’ is a sensible 1.9, that also means the engine has no extreme advantage over other game engines I possess. They all tend to be of the vanilla variety, that offer OpenGL 2 / DirectX 9c… – GL 3 would be equivalent to Dx 10, and GL equivalent to Dx 11.

Speaking of vanilla, I also installed the latest snapshot of Crystal Space on ‘Klystron': Version 2.1 ! I am amazed at how much better this latest build of Crystal Space seems, in terms of being stable when compiled, than earlier builds of it were.