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02-26-2002, 05:58 AM
I was coding a simple program drawing af chessboard of lines having enabled GL_LINE_SMOOTH, but it didn't work. The lines were still jerky. The same code seemed to work on another computer though.

So how can I check to see which features my gfx card supports? And does som gfx cards really not support smooth lines, or is my code probably just buggy? Knowing so, will save alot of struggeling for trying to make features work that never will anyway..

Thanks

Bob
02-26-2002, 06:20 AM
Did you enable blending, with proper blend function? Line smooth requires blending to work properly.

Trying to get a list of supported features is a problem, cause the list depends on what you mean by supported. If you want to know what your implementation can do, then download the OpenGL specification document for the version your implementation supports and have a look there. Everything in there should be supported. Just note that some things might not be not supported by your hardware (and therefore maybe not usable in practice). It all depends on where you define the edge between supported and not supported.

02-26-2002, 06:35 AM
Thanks for the tip, with blendfunc enabled (and hardware acceleration disabled) things work just fine! This is alarming news tough, coz this means that when something's not working, it might just be the gfxcard.. Guess I need experience, thanks again though!

marcus256
02-27-2002, 03:31 AM
Some graphics cards (or drivers for them) are particularly bad at some things. I am running a Matrox G200 on an NT 4 PC (driver is MCD, not a complete ICD). On this card I always get totally black geometry (non-visible) if I enable fog - which should be supported by OpenGL 1.1 (which is what it sais if I glGetString( GL_VERSION ) ). I have also noted that "thick" lines (glLineSize(x), where x > 1.0) gives very low performance (probably software rendering instead of hardware), etc. etc.

The first thing (fog) is an example of a bad driver.

The second thing (slow line-drawing) is an example of the driver being forced to do software rendering because there is no hardware support for a special feature. In this case I would still say that the feature (thick lines) is supported, it's just "poorly supported" since it is dead slow.

marcus256
02-27-2002, 03:37 AM
One other thing - some OpenGL functionality may be implemented differently on different cards/drivers simply because the specification does not always specify exactly how (or to what precision) something should be implemented. Line anti-aliasing is one example. See this page: http://www.3dlabs.com/product/technology/wildcat_quality.htm (I wish I had a Wildcat!).