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Software Quake MDL Frame Interpolation

Postby mh » Fri Jun 25, 2010 11:30 am

In case anyone missed it. ;)

Software Quake Frame Interpolation

This is a code-dump of an r_alias.c that does frame interpolation, together with a few implementation notes on changes required elsewhere to support it. I was going to do a tutorial, but the changes throughout the code are quite extensive, and most of them are just one or two lines, so it's easier for all of us to just give the full code and let you attack it with your favourite diff tool.

You should be pretty much able to just "drop-n-go" this into a standard ID software Quake codebase.

It doesn't do anything fancy like attempting to fix up muzzleflashes, and doesn't cover movement/orientation interpolation; the old interpolation tutorial can be used for that quite effectively (just move the changes from R_RotateForEntity to CL_RelinkEntities).
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Re: Software Quake MDL Frame Interpolation

Postby Baker » Fri Jun 25, 2010 11:41 am

mh wrote:In case anyone missed it. ;)

Software Quake Frame Interpolation

This is a code-dump of an r_alias.c that does frame interpolation, together with a few implementation notes on changes required elsewhere to support it. I was going to do a tutorial, but the changes throughout the code are quite extensive, and most of them are just one or two lines, so it's easier for all of us to just give the full code and let you attack it with your favourite diff tool.

You should be pretty much able to just "drop-n-go" this into a standard ID software Quake codebase.

It doesn't do anything fancy like attempting to fix up muzzleflashes, and doesn't cover movement/orientation interpolation; the old interpolation tutorial can be used for that quite effectively (just move the changes from R_RotateForEntity to CL_RelinkEntities).


Haha :D :D :D OMG!

Awesome!

I might tutorialize this and turn it into a cvar if possible. Now if only I could find the code for movement interpolation (it's buried in some version of JoeQuake or aguirReQuake).

Extra info: JoeQuake Build 1862 has lightstyle interpolation according to the docs even for software renderers. Not that I noticed ... I guess my eye isn't trained as to quite notice it -- I suppose I'd need to find a flickering light or glowing orb or something.

Anyways, thanks!
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Postby mh » Fri Jun 25, 2010 12:04 pm

Oh, I've had lightstyle interpolation for years! :lol:

It's really easy, just a small change in R_AnimateLight.

The old QER interpolation tutorial was saved here: http://www.quakewiki.net/archives/qer/tutorial4.html :D
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Postby Baker » Fri Jun 25, 2010 1:01 pm

Works like a charm!

Your documentation in the .zip is perfect, no good reason to do a tutorial of it or anything ... although I'm going to attempt to use this with a cvar.
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Postby mh » Fri Jun 25, 2010 1:27 pm

Good to hear!

I should mention that I changed the names of some entity_t members; from pose1 and pose2 to lastpose and currpose. I never was happy with the names that the QER tutorial used; not descriptive enough! :D

It shouldn't be that big a deal as I wouldn't imagine that too many people have done interpolation in software Quake, but you'll need to know it if you're ever planning on integrating the two.
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Postby Spike » Fri Jun 25, 2010 1:28 pm

[offtopic]tbh, I'm not that keen on lightstyle interpolation. makes flickering lights look ugly, and the lightmap uploads/regeneration every single frame gives a biiig slowdown.[/offtopic]

I thought NQ had fully functional movement/angles interpolation already...
All but for stepping monsters, which have an explicit flag set that stops them from being interpolated so they don't slide and judder, but merely judder. Just ignore that flag if frame interpolation is active.
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Postby Baker » Fri Jun 25, 2010 1:39 pm

mh wrote:Good to hear!

I should mention that I changed the names of some entity_t members; from pose1 and pose2 to lastpose and currpose. I never was happy with the names that the QER tutorial used; not descriptive enough! :D


I figured that out before reading your readme.txt. I don't like names that aren't descriptive either.

I might add that animation interpolation without movement interpolation looks even worse than having neither.

Btw ... JoeQuake doesn't seem to have it, I think I was mistaken thinking it had movement interpolation in the software version but rather render.h had an #ifdef GLQUAKE removed in 0.15 so maybe I just assumed.

Spike wrote:[offtopic]tbh, I'm not that keen on lightstyle interpolation. makes flickering lights look ugly, and the lightmap uploads/regeneration every single frame gives a biiig slowdown.[/offtopic]


Eh well then maybe I won't implement that in software either. I loaded up JoeQuake (Software renderer version) and was trying to see if I could tell the difference.

All but for stepping monsters, which have an explicit flag set that stops them from being interpolated so they don't slide and judder, but merely judder. Just ignore that flag if frame interpolation is active.


Hmmmm. Could you explain this more?

See I hate interpolation in NetQuake deathmatch multiplayer and in NQ multiplayer (online) coop the monster movements look ugly as hell even with interpolation and is completely jerky.

What flag is this? The movetype? At least it would solve one of the strange mysteries of the universe.)
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Postby mh » Fri Jun 25, 2010 2:38 pm

The movement/angles interpolation in NQ just determines the time between two intervals that messages arrive at, and isn't active when connected to a local server, so it's quite limited really.

I reckon the thing with interpolation is that it's all a matter of personal taste. Me, I hate the absence of frame interpolation, but could live without movement/angles easily enough (not saying that I prefer to switch it off - I don't, but it doesn't bother me so much if it's not available). Doesn't mean that I'm right and you're wrong, or vice-versa; just personal taste.
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Postby Baker » Fri Jun 25, 2010 3:34 pm

Spike wrote:[offtopic]tbh, I'm not that keen on lightstyle interpolation. makes flickering lights look ugly, and the lightmap uploads/regeneration every single frame gives a biiig slowdown.[/offtopic]

I thought NQ had fully functional movement/angles interpolation already...
All but for stepping monsters, which have an explicit flag set that stops them from being interpolated so they don't slide and judder, but merely judder. Just ignore that flag if frame interpolation is active.


Son a bitch! The U_NOLERP flag. Testing ... sigh ... of course.

Spike, thank you for your priceless advice. Sheesh. Ages old mystery solved at least for me today. Grrrrrr. :evil:
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Postby Spike » Fri Jun 25, 2010 9:17 pm

Yup, that's the flag that I was thinking of, anyway.
mh has a point though - it depends upon your packet rate.

[offtopic]And you might as well implement lightstyle smoothing, if disabled, its only one cvar check per frame, just maybe not default it to enabled. Some people prefer it, but yeah, flickering torches. Or if you like hacks, you could interpolate based on difference between the styles, if its too different, no interpolation. The expense is in the lightmaps, not the actual lightstyle values themselves.[/offtopic]
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Postby mh » Sat Jun 26, 2010 1:44 am

Spike wrote:[offtopic]And you might as well implement lightstyle smoothing, if disabled, its only one cvar check per frame, just maybe not default it to enabled. Some people prefer it, but yeah, flickering torches. Or if you like hacks, you could interpolate based on difference between the styles, if its too different, no interpolation. The expense is in the lightmaps, not the actual lightstyle values themselves.[/offtopic]

[offtopic]It occurs to me that many of the lightstyles in Quake are not actually meant to be interpolated. Maybe the slow pulses, yes, but flickering torches and strobes? No way.[/offtopic]
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Postby Baker » Sat Jun 26, 2010 12:31 pm

http://www.quake-1.com/docs/rendering/r_alias.c

Managed to turn it into a cvar. My software renderer code is about 98% the same as stock WinQuake and while this file alone isn't the complete implementation (a couple of small adjustments to 3 or 4 other files, 1 or 2 liners).

It gives a good illustration for a third party (i.e., not either of you two obviously, hahaha) of how I turned it into a cvar and how I can optionally simply not even compile it into the engine.

I added cl_gameplayhack_monster_lerp 1 (as default value) and sv_gameplayfix_monster_lerp 1 (as default value) into my engine [GL builds too, of course].

Combined with MH interpolation, those deliver a much better single player experience in software and at any of the 3 or 4 NQ online coop servers (killing U_NOLERP ... sigh, what a difference).

That is really some wonderful code, MH. :D
Last edited by Baker on Sat Jun 26, 2010 12:35 pm, edited 2 times in total.
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Postby leileilol » Sat Jun 26, 2010 12:34 pm

mh wrote:
Spike wrote:[offtopic]And you might as well implement lightstyle smoothing, if disabled, its only one cvar check per frame, just maybe not default it to enabled. Some people prefer it, but yeah, flickering torches. Or if you like hacks, you could interpolate based on difference between the styles, if its too different, no interpolation. The expense is in the lightmaps, not the actual lightstyle values themselves.[/offtopic]

[offtopic]It occurs to me that many of the lightstyles in Quake are not actually meant to be interpolated. Maybe the slow pulses, yes, but flickering torches and strobes? No way.[/offtopic]

[offtopic]Interpolating lightstyles kill 486s and non-Pentiums, so don't do it![/offtopic]
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Postby Baker » Sat Jun 26, 2010 12:49 pm

It sounds light it would screw up the intended look and feel anyway.

MH Interpolation Performance Results

timedemo demo1

No animation interpolation @ 320x200 fullscreen my machine: 285 FPS
With animation interpolation @ 320x200 fullscreen my machine: 281 FPS

So despite the lack of assembly and the pure C nature of the interpolation code, scarcely makes an FPS dent.

And even though the changes in r_alias.c are a bit moderate, it is still a rather light modification and --- well --- it isn't scary from a point of view of stability or compatibility. :D :D
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Postby mh » Sat Jun 26, 2010 2:53 pm

leileilol wrote:
mh wrote:
Spike wrote:[offtopic]And you might as well implement lightstyle smoothing, if disabled, its only one cvar check per frame, just maybe not default it to enabled. Some people prefer it, but yeah, flickering torches. Or if you like hacks, you could interpolate based on difference between the styles, if its too different, no interpolation. The expense is in the lightmaps, not the actual lightstyle values themselves.[/offtopic]

[offtopic]It occurs to me that many of the lightstyles in Quake are not actually meant to be interpolated. Maybe the slow pulses, yes, but flickering torches and strobes? No way.[/offtopic]

[offtopic]Interpolating lightstyles kill 486s and non-Pentiums, so don't do it![/offtopic]

Does anybody aside from you use these regularly these days? :lol: :lol: :lol:

[ontopic]It's really kinda weird looking at frame interpolation in software Quake, isn't it?[/ontopic]
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