Framerate drops...

[Almasy]

Well, this may seem stupid, but what causes framerates to drop? Since I was discussing this with a person that said game X couldn´t be made on PS2 from the ground up and look like the GCN version without framerate drops and a lot of jaggies.
He is not much of a person that knows about hardware, so I didn´t took him very seriously, but then I began to wonder what causes them? More polygons than the engine can handle on-screen? More particle effects? If so, what about when framerate sometimes drops when nothing important is happening?
Oh, BTW, now that I´m displaying my ignorance, can someone clarify me what procedural textures and radiosity lightning are? I´ve seen people mention them in next-gen machines discussions and I have no idea what they mean.

 

[jvd]

Well, this may seem stupid, but what causes framerates to drop? Since I was discussing this with a person that said game X couldn´t be made on PS2 from the ground up and look like the GCN version without framerate drops and a lot of jaggies.
He is not much of a person that knows about hardware, so I didn´t took him very seriously, but then I began to wonder what causes them? More polygons than the engine can handle on-screen? More particle effects? If so, what about when framerate sometimes drops when nothing important is happening?
Oh, BTW, now that I´m displaying my ignorance, can someone clarify me what procedural textures and radiosity lightning are? I´ve seen people mention them in next-gen machines discussions and I have no idea what they mean.

um its basicly to much on the screen at once. Mostly when you hit your fillrate limit. if you have a 1000mpixels persecond and u need to drap 1100mpixels persecond its going to slow the framrate down. Same goes with polygons textrues , particle efects... basicly anything .. even a.i can cause frame drops

 

[evil]

On today's hardware ? Lazy programming, mostly

 

[mech]

What I want to know is why some games have hitches where there doesn't seem to be any change on screen, and it doesn't appear to be loading data or anything.

 

[London Geezer]

What I want to know is why some games have hitches where there doesn't seem to be any change on screen, and it doesn't appear to be loading data or anything.

YEP, that makes me wonder as well sometimes.... there must be some loading going on, it's the only explanation, music or stuff like that.... :? right...?

 

[jvd]

What I want to know is why some games have hitches where there doesn't seem to be any change on screen, and it doesn't appear to be loading data or anything.

YEP, that makes me wonder as well sometimes.... there must be some loading going on, it's the only explanation, music or stuff like that.... :? right...?

mabye its already starting to load the next room into memory ? or mabye there was a memory leak ... reasons could go on and on. Mostly poor programing but programers and game testers can't catch everything

 

[ERP]

Frame rate drops can be caused by almost anything.

The simple answer is when the machine runs out of resources for a given frame.
This could be CPU time (most likely), Fill Rate, Triangle Rate, Memory bandwidth, waiting on some sort of streaming etc etc.

Because of the interdependancies, it's possible to run resources while still having plenty of the individual resources available. This is generally the case when the code doesn't effectively exploit the parallelism in the system.

In even simple games there can be a HUGE variation in scene content frame to frame, and in general it simply isn't predictable.

 

[Lazy8s]

Programs sometimes get tripped up for reasons not represented on screen. Complex or unexpected interactions within the game world can cause parts of the program to become trapped in cycles where the calculation requirements start exponentially increasing out of check, looping the computer into madness and slowing everything down even in seemingly simple on-screen environments. Bugs, programming inefficiencies, or functions and subroutines that don't properly terminate can bring the sweet music of a smoothly executing program to a grinding halt.

 

[overclocked]

The last mission in Halo when you drive the jeep. oh god. 8)

 

[Tagrineth]

Think of it like this:

Ideally, you'd get 60 frames in one second. So each frame would take 1/60 of a second.

Let's say the video hardware can sustain 60 million polys/sec. That means each frame has to have less than 1 million polygons for 60fps.

NOW, let's say that suddenly some kind of effect is used that results in the poly count doubling to 2 million polys. That means the video hardware has to spend twice as much time working, resulting in the frame time doubling, from 1/60 to 2/60 or 1/30 of a second - the frame rate will 'drop' to 30fps at that instant and there will be a noticeable jerk.

Now let's say you quadrupled the poly count - to 4 million polys in the frame. Now the video hardware has to spend four times as long setting them up, so you go from 1/60 to 4/60 or 1/15 of a second. Suddenly you're at 15fps - a very noticeable jerk.

Now, replace polygons with pixels, or CPU operations, or blah blah blah and you get what causes FPS drops.