Celestia on Mac OS X 10.2 (Jaguar)

[HankR]

Sad to say, Mac OS X 10.2 (Jaguar) appears to be bad news for the current Mac OS X version of Celestia.

- Hank

[HankR]

Actually, it's not as bad as I thought. The GLUT modifer key mappings have changed, and seem flakier than before, but the forthcoming Cocoa version of Celestia should fix this. There are some rendering anomalies at the poles of some objects. I'm not sure if this was there before, and it may be fixed in the latest version of Celestia. Apple's new version of OpenGL supports many new extensions so hopefully we'll eventually see some enhanced rendering with newer versions of Celestia. In the long term, Apple's heavy commitment to OpenGL should be a plus. The most serious problem I have is that the 8K earth texture no longer works (on my 128MB GF4Ti). I suspect this may be because 10.2 uses OpenGL textures for OS window compositing. If so, it could be a long-term problem for texture-intensive OpenGL apps like Celestia.

- Hank

[Matt McIrvin]

I just succeeded in freezing my Mac really hard (as in, not responsive to the power button-- I had to yank the cord) by intentionally overtaxing my video card with giant Galilean moon textures. My wild guess is that this is what it looks like when Quartz Extreme (the new Jaguar feature which hijacks the 3D hardware for user interface acceleration) cries uncle as a result of texture memory filling up. If so, this bodes ill for gamers unless Apple can fix it really soon.

My machine is a slightly unusual configuration, dual 1GHz early 2002 Quicksilver downgraded to the Radeon 7500.

[HankR]

My understanding now is that all OpenGL applications share VRAM (graphics card memory), with memory management by the OS. Quartz Extreme has no special priority. But I suspect very large textures can cause problems due to thrashing/fragmentation issues.

If you've installed the Developer Tools, there's an interesting utility application '/Developer/Applications/OpenGL Profiler' that lets you display memory usage and various other parameters of the OpenGL driver in real time. Very interesting to watch.

- Hank

[Rickster]

If so, this bodes ill for gamers unless Apple can fix it really soon.

Not so much for gamers: most GL games are fullscreen, and thus get the GPU/VRAM entirely to themselves. It's windowed GL apps like Celestia or 3D authoring environments that will have issues because of this.

One of the things OpenGL in Jaguar does (or maybe it's just the Quartz Extreme window server) is run a virtual memory like scheme for texture memory, swapping window buffers between main memory and VRAM.

It uses DMA, so the massive data transfers don't go through a CPU bottleneck, but I gather it's really only fast enough to matter on newer system architectures -- I've got a dual-500 G4 with Radeon 8500, but minimizing a large Celestia window just completely borks the machine. I'm guessing I need either AGP 4x, a faster system bus, or a better logic board controller.

[Matt McIrvin]

That explains a lot. I just had another serious freeze, this time not as hard, when an OpenGL screensaver came up while Celestia was open. It's probably thrashing on the video RAM.

I'm starting to wish that Quartz Extreme could be disabled with some simple system preference. My machine was pretty fast to begin wth so it's not providing a gigantic performance benefit for me, and it seems to create problems with demanding use of OpenGL.