OpenGL 1.3 and 2.0: performance improvements but what are the differences?

In the video settings menu you can disable OpenGL 2.0 (vid_gl20 0), this reverts to OpenGL 1.3. This is useful when troubleshooting performance, quality and stability issues. I have some very obscure old hardware, some of which predates the early modern period, hence I find this setting useful.

It's worth trying on any old/slow hardware to see if it improves performance. Ronan went from 38 up to 103 on an old laptop with a Radeon X2300! I've had a 20% difference with a Geforce FX.

Now I know that many effects are disabled by this. We always talk about normal setting and above not working fully without OpenGL 2.0 or later. Also reflections don't work which are more importantly required for teleporters like those in Stormkeep. Is it a problem to be running without OpenGL 2.0? I know it's not ideal graphically and there is no competitive gameplay advantage that I can see but it's better than a system not being usable at all or playing under omg.

It does however raise the question if low and medium settings are compatible with the OpenGL 1.3 path due to the missing reflections.

Also there is vid_gl13 reachable in the console. Again, I can see some performance/stability advantage to be had on very old hardware but is there anything wrong with setting this to zero? What are the graphical differences that could be seen? I've noticed some z-fighting where you wouldn't normally expect.

I'm wondering if this may be a useful troubleshooting option for netbooks and other systems with onboard graphics so would it be worth changing the OpenGL 2.0 option in the video menu to include this as an option too?

Just curious on a whole load of things here.

vid_gl13 0 (the OpenGL 1.1 path) does virtually nothing, but should usually be a bit slower. It's mainly for tracking down driver bugs.

vid_gl20 0 (the OpenGL 1.3 path) however is a large change, but lacks some features.

As for "It does however raise the question if low and medium settings are compatible with the OpenGL 1.3 path due to the missing reflections.": maps that rely on the reflection effect for gameplay force the effect on by map-specific configuration. So the low config is even fully playable on these.

Thanks div. I can understand why you would expect dropping back to a lower GL version to be slower when working with a good implementation. This is why it surprises me that even with the NVIDIA driver OpenGL 1.1 could be the fastest in this case. There does seem a be a lack of precision in the 1.1 path with z-fighting and sparklies at times but from back in the day when we had things like gl_ztrick, the performance impact was always close to zero when working with these.

There does seem to be an inconsistency in Darkplaces whereby if OpenGL 2.0 is not detected, the 1.30 path is used yet if OpenGL 1.3 is not detected, the 1.3 path is still used, not the 1.1 path. Not sure if this is by design or not.

I didn't know that reflections were forced on some map configs. This however would not work around reflections not being available due to OpenGL 1.x being used? I've certainly seen Stormkeep without reflections when vid_gl20 0 is used.

I've looked some more at OpenGL 1.3 and seem to be coming into more and more problems. Not just the Lightspeed fog issue already reported.

I know div has already said that reflections will be forced on for maps where they are needed but I don't seem to be finding this happen when OpenGL 2 is disabled. Look at this in glowpant for example:

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The warp zones as well as any teleporters get rendered with this texture here. The other side of that warp zone are 2 bots looking right at me so this is heavily impacting gameplay. Is it just me seeing this? All I am doing to get this effect on glowplant is running with OpenGL 2 disabled, a vid_restart is required too. I've seen this on every system I've tried on.

In addition I have noticed some strange textures with explosions in the 1.3 path. Black polygons flash for a frame or two. May this is just down this particular driver having an issue but explosions shouldn't be black. Electro explosions are also pretty odd.

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Where I'm concerned here is that the OpenGL 1.3 path is included and accessible from the video menu yet there are issues which exist that are not spotted for some time and may be difficult to resolve. Does this mean that the OpenGL 1.3 path should be considered deprecated? Clearly very few people use it these days and so trying to support it becomes a problem if it is not frequently used and tested. Any setup than needs the 1.3 path is going struggle with the game anyway so is it worth bothering with?