Digital Foundry Retro Discussion [2016 - 2017]

[Nesh]

New DF Retro article featuring Soul Calibur. Played the Sould Edge version -PS1- at my best friend's house around 1998-99, I think?

I was totally impressed and the game was soooo good, the spectacular intro and the game's gameplay was nearly flawless. Perhaps the fighting game that impressed me the most ever, after Super Street Fighter 2 Turbo, which was released before.

Then Dead or Alive 3 on the Xbox impressed me again -not only 'cos of the grahics - and I can't recall a fighting game that looked so good afterwards. If anything Super Street Fighter 2 Turbo HD for the X360 looked very nice to me, art style too.

What I really want to see is an analysis on Tekken Tag Tournament 1.
No game on PS2 had such an amazing rendering of materials. It was the best example of close to PBR on the PS2 we ever got IMO. Fabric looked like fabric, metal looked like metal, wood looked like wood, skin looked like skin (true ogre vs humans) etc.
And some effects even gave the impression of bump mapping. Textures were also super clean super detailed.
The character polygon numbers were probably higher than the rest of Tekken games. The only fighting game on the PS2 which probably rivalled it overall was Soul Calibur 3

 

[Cyan]

What I really want to see is an analysis on Tekken Tag Tournament 1.
No game on PS2 had such an amazing rendering of materials. It was the best example of close to PBR on the PS2 we ever got IMO. Fabric looked like fabric, metal looked like metal, wood looked like wood, skin looked like skin (true ogre vs humans) etc.
And some effects even gave the impression of bump mapping. Textures were also super clean super detailed.
The character polygon numbers were probably higher than the rest of Tekken games. The only fighting game on the PS2 which probably rivalled it overall was Soul Calibur 3

upon reading your post I have been searching for info about Tekken Tag Tournament 1 but I can't recall whether I played it or not. My best childhood friend had the PS1 and then got the PS2 so I probably played it. But my most vivid memories of Tekken are from the original PS1 version, which I played at the house of this friend, and how impressive it was at the time. While I wasn't a fan of the art style of the original Tekken, it was a landmark for the 3D fighting genre.

Virtua Fighter on the PC and especially Battle Arena Toshinden impressed me before Tekken 1 iirc. That or maybe I had seen Tekken before in the arcades, just like my friend, who loved the game and then bought the PS1 version which was basically "arcade perfect"? It is one of those game that made you think that consoles were achieving arcade parity.

That friend also had the Megadrive and got Virtua Racing for it -a very addictive game despite only having 3 tracks and the mirror mode, but beating your best time kept it very interesting-. but that wasn't close to being arcade perfect.

 

[Nesh]

upon reading your post I have been searching for info about Tekken Tag Tournament 1 but I can't recall whether I played it or not. My best childhood friend had the PS1 and then got the PS2 so I probably played it. But my most vivid memories of Tekken are from the original PS1 version, which I played at the house of this friend, and how impressive it was at the time. While I wasn't a fan of the art style of the original Tekken, it was a landmark for the 3D fighting genre.

Virtua Fighter on the PC and especially Battle Arena Toshinden impressed me before Tekken 1 iirc. That or maybe I had seen Tekken before in the arcades, just like my friend, who loved the game and then bought the PS1 version which was basically "arcade perfect"? It is one of those game that made you think that consoles were achieving arcade parity.

That friend also had the Megadrive and got Virtua Racing for it -a very addictive game despite only having 3 tracks and the mirror mode, but beating your best time kept it very interesting-. but that wasn't close to being arcade perfect.

Tekken 1 and 2 if I recall were arcade perfect games since the arcade itself was a PS1. I have to admit though that Battle Arena Toshinden (that and Wipeout was the first games I purchased my PS1 with) impressed me even more than Tekken 1 with its beautiful 3D backgrounds, ability to sidestep, beautiful lighting and some pretty amazing effects. Tekken 1 was flat looking in every way. The animations is what made it special though. I believe it was mostly motion captured back then.
But I ll never forget how awesome the boss stage looked in BAT. Nothing could come close on the PS1 for a while

But Tekken Tag Tournament was visually perfect in every way. For the young gamer back in the day, that looked almost as good as the CG intros of Tekken on PS1. In some respects it probably was as good. I wish I could find the video with the stage demonstrations Namco was releasing back in the day to showcase the graphics but they don't seem to exist on Youtube

As a reference this is how the Arcade version looked. Also system 12 like the original Soul Calibur on the arcades

The improvement was even bigger than between SC Arcade and the DC version. And it also even surpassed DC's Soul Calibur in pretty much everything in terms of sheer detail, effects and lighting. It made the PS2 look like a generational leap over DC. I was wondering back then how future Tekken games will look like after TTT, considering the difference between T1 and T3 on PS1.
To my disappointment no Tekken on the PS2 came close either

 

[Cyan]

Tekken 1 and 2 if I recall were arcade perfect games since the arcade itself was a PS1. I have to admit though that Battle Arena Toshinden (that and Wipeout was the first games I purchased my PS1 with) impressed me even more than Tekken 1 with its beautiful 3D backgrounds, ability to sidestep, beautiful lighting and some pretty amazing effects. Tekken 1 was flat looking in every way. The animations is what made it special though. I believe it was mostly motion captured back then.
But I ll never forget how awesome the boss stage looked in BAT. Nothing could come close on the PS1 for a while

But Tekken Tag Tournament was visually perfect in every way. For the young gamer back in the day, that looked almost as good as the CG intros of Tekken on PS1. In some respects it probably was as good. I wish I could find the video with the stage demonstrations Namco was releasing back in the day to showcase the graphics but they don't seem to exist on Youtube

As a reference this is how the Arcade version looked. Also system 12 like the original Soul Calibur on the arcades

The improvement was even bigger than between SC Arcade and the DC version. And it also even surpassed DC's Soul Calibur in pretty much everything in terms of sheer detail, effects and lighting. It made the PS2 look like a generational leap over DC. I was wondering back then how future Tekken games will look like after TTT, considering the difference between T1 and T3 on PS1.
To my disappointment no Tekken on the PS2 came close either

didn't expect the generational leap to be so noticeable, but watching the arcade version and then the PS2 version is night and day. I am surprised by the fact that there seem to be some bump mapping on the ground textures. iirc the Matrox G400 was the first PC graphics card to feature native bump mapping support. There was a free game bundled with my Matrox G400 32MB which was meant to show that feature. That's why I find it even more surprising that similar effects were used in the PS2 at the time.

Maybe Tekken Tag Tournament was the beginning of the end of the days when coin-ops were basically the only way to play the latest video games.

 

[Nesh]

didn't expect the generational leap to be so noticeable, but watching the arcade version and then the PS2 version is night and day. I am surprised by the fact that there seem to be some bump mapping on the ground textures. iirc the Matrox G400 was the first PC graphics card to feature native bump mapping support. There was a free game bundled with my Matrox G400 32MB which was meant to show that feature. That's why I find it even more surprising that similar effects were used in the PS2 at the time.

Maybe Tekken Tag Tournament was the beginning of the end of the days when coin-ops were basically the only way to play the latest video games.

Thats the peculiar thing with Tekken Tag. Some details on the ground were made out of polygons. At the same time some effects do suggest the simultaneous use of something else which may be bump mapping or some clever technique.
There was no other game on the PS2 which clearly demonstrated such a similar effect except Matrix Path of Neo.
Long debates did not conclude that the PS2 could do bump mapping.
It is also amazing how the specularity behaves differently in relation to the camera angle and the light sources. i.e it is blueish from one side and reddish on the other (edit in the video above). The same principles applied on clothing such as Lei's silk apparel.
But here and behold the way Tekken Tag Tournament renders its graphics stands out like an outlier compared to anything on the PS2 and it was one of its very first games. It is like NAMCO bought into the next generation hype, ignored the idea of limitations and tried to pump as many effects as possible that were originally done only through video game CG.

Other examples:
The wood on the ground does not look flat. The plunks' edges give the impression of extrusion whereas the center gives the impression of convex. Also notice that the light behaved differently on each piece instead of treating the ground as one surface
http://vignette1.wikia.nocookie.net/tekken/images/d/d4/Jin=b_orrr.jpg/revision/latest?cb=20150322204106&path-prefix=en

Similar effect here
http://4.bp.blogspot.com/-fAUNyNwtYM0/TgWqv-rdASI/AAAAAAAAA8k/zKk9DcuWvjo/s1600/001.jpg

Here is another example of the ground where there are little metal extrusions on the ground.

 

[Cyan]

Thats the peculiar thing with Tekken Tag. Some details on the ground were made out of polygons. At the same time some effects do suggest the simultaneous use of something else which may be bump mapping or some clever technique.
There was no other game on the PS2 which clearly demonstrated such a similar effect except Matrix Path of Neo.
Long debates did not conclude that the PS2 could do bump mapping.
It is also amazing how the specularity behaves differently in relation to the camera angle and the light sources. i.e it is blueish from one side and reddish on the other (edit in the video above). The same principles applied on clothing such as Lei's silk apparel.
But here and behold the way Tekken Tag Tournament renders its graphics stands out like an outlier compared to anything on the PS2 and it was one of its very first games. It is like NAMCO bought into the next generation hype, ignored the idea of limitations and tried to pump as many effects as possible that were originally done only through video game CG.

Other examples:
The wood on the ground does not look flat. The plunks' edges give the impression of extrusion whereas the center gives the impression of convex. Also notice that the light behaved differently on each piece instead of treating the ground as one surface
http://vignette1.wikia.nocookie.net/tekken/images/d/d4/Jin=b_orrr.jpg/revision/latest?cb=20150322204106&path-prefix=en

Similar effect here
http://4.bp.blogspot.com/-fAUNyNwtYM0/TgWqv-rdASI/AAAAAAAAA8k/zKk9DcuWvjo/s1600/001.jpg

Here is another example of the ground where there are little metal extrusions on the ground.

Those effects are out of this world for a PS2. Really. Is that for real? The last image is a great example, but this one looks like real wood, like real world laminate flooring. If you get rid of the HUD and the characters it could pass up as a real life image of a real life place, specially the parquet flooring, and the wooden columns. The light refraction off of the surface of the laminate flooring looks perfect.

 

[Megadrive1988]

Tekken 1 and 2 if I recall were arcade perfect games since the arcade itself was a PS1. I have to admit though that Battle Arena Toshinden (that and Wipeout was the first games I purchased my PS1 with) impressed me even more than Tekken 1 with its beautiful 3D backgrounds, ability to sidestep, beautiful lighting and some pretty amazing effects. Tekken 1 was flat looking in every way. The animations is what made it special though. I believe it was mostly motion captured back then.
But I ll never forget how awesome the boss stage looked in BAT. Nothing could come close on the PS1 for a while

But Tekken Tag Tournament was visually perfect in every way. For the young gamer back in the day, that looked almost as good as the CG intros of Tekken on PS1. In some respects it probably was as good. I wish I could find the video with the stage demonstrations Namco was releasing back in the day to showcase the graphics but they don't seem to exist on Youtube

As a reference this is how the Arcade version looked. Also system 12 like the original Soul Calibur on the arcades

The improvement was even bigger than between SC Arcade and the DC version. And it also even surpassed DC's Soul Calibur in pretty much everything in terms of sheer detail, effects and lighting. It made the PS2 look like a generational leap over DC. I was wondering back then how future Tekken games will look like after TTT, considering the difference between T1 and T3 on PS1.
To my disappointment no Tekken on the PS2 came close either

Although it's nitpicking, Tekken and Tekken 2 (as well as Soul Edge / Blade) were not technically arcade perfect, although for all practical purposes, they were, not to mention all the additions for the console versions of those games.

I mention this because, although all 3 games ran on the PlayStation-based Namco System 11 board, the System 11 board had 2 MB of VRAM, whereas the PlayStation console had just 1 MB VRAM.

http://system16.com/hardware.php?id=533
https://en.wikipedia.org/wiki/Namco_System_11

If you compare the arcade System 11 versions of Tekken and especially Tekken 2 with the console versions, you'll notice the texture resolution is lower on the floors of the background stages.

Other things like the hit sparks and effects, in T1 & T2, are also lower resolution in the console versions.

Obviously the difference between the System 12 board used in Tekken 3 and Soulcal. were greater, because System 12's CPU ran 1.5X faster.
Therefore the difference between Tekken 3 arcade and PlayStation are much more noticeable (lower polygon models, lack of 3D backgrounds, etc).

 

[Nesh]

Those effects are out of this world for a PS2. Really. Is that for real? The last image is a great example, but this one looks like real wood, like real world laminate flooring. If you get rid of the HUD and the characters it could pass up as a real life image of a real life place, specially the parquet flooring, and the wooden columns. The light refraction off of the surface of the laminate flooring looks perfect.

Exactly

 

[Nesh]

Although it's nitpicking, Tekken and Tekken 2 (as well as Soul Edge / Blade) were not technically arcade perfect, although for all practical purposes, they were, not to mention all the additions for the console versions of those games.

I mention this because, although all 3 games ran on the PlayStation-based Namco System 11 board, the System 11 board had 2 MB of VRAM, whereas the PlayStation console had just 1 MB VRAM.

http://system16.com/hardware.php?id=533
https://en.wikipedia.org/wiki/Namco_System_11

If you compare the arcade System 11 versions of Tekken and especially Tekken 2 with the console versions, you'll notice the texture resolution is lower on the floors of the background stages.

Other things like the hit sparks and effects, in T1 & T2, are also lower resolution in the console versions.

Obviously the difference between the System 12 board used in Tekken 3 and Soulcal. were greater, because System 12's CPU ran 1.5X faster.
Therefore the difference between Tekken 3 arcade and PlayStation are much more noticeable (lower polygon models, lack of 3D backgrounds, etc).

Never noticed the difference before since they are so close.
But yeah Tekken 3 was a different case

 

[Sigfried1977]

Tekken 1 and 2 if I recall were arcade perfect games since the arcade itself was a PS1. I have to admit though that Battle Arena Toshinden (that and Wipeout was the first games I purchased my PS1 with) impressed me even more than Tekken 1 with its beautiful 3D backgrounds, ability to sidestep, beautiful lighting and some pretty amazing effects. Tekken 1 was flat looking in every way. The animations is what made it special though. I believe it was mostly motion captured back then.
But I ll never forget how awesome the boss stage looked in BAT. Nothing could come close on the PS1 for a while

But Tekken Tag Tournament was visually perfect in every way. For the young gamer back in the day, that looked almost as good as the CG intros of Tekken on PS1. In some respects it probably was as good. I wish I could find the video with the stage demonstrations Namco was releasing back in the day to showcase the graphics but they don't seem to exist on Youtube

As a reference this is how the Arcade version looked. Also system 12 like the original Soul Calibur on the arcades

The improvement was even bigger than between SC Arcade and the DC version. And it also even surpassed DC's Soul Calibur in pretty much everything in terms of sheer detail, effects and lighting. It made the PS2 look like a generational leap over DC. I was wondering back then how future Tekken games will look like after TTT, considering the difference between T1 and T3 on PS1.
To my disappointment no Tekken on the PS2 came close either

Tekken 5 looked amazing in its own right, though.

Second screen is from Dark Resurrection, but higher resolution aside, the assets are pretty much the same.

 

[Nesh]

Tekken 5 looked amazing in its own right, though.

Second screen is from Dark Resurrection, but higher resolution aside, the assets are pretty much the same.

To me it looks like a big downgrade next to TTT

 

[Cyan]

Tekken 5 looked amazing in its own right, though.

Second screen is from Dark Resurrection, but higher resolution aside, the assets are pretty much the same.

just like in the previous post, I don't find anything noteworthy there, compared to Tekken Tag Tournament, the ground textures look much muddier and maybe only the characters look better. Was your point to show the characters details? Or the dragon head?

 

[Cyan]

Is Duke Nukem 3D a true 3D game or a 2D game?

I have a 21 years old friend who told me today's morning that he learnt yesterday -contrary to what he thought his entire life- that Doom isn't a 3D game. Well, I always knew that I told him. I played around a lot with Doom editors and learnt many things about the engine, map creation and stuff. Everything was 2D, everything had a ceil and a floor.

I barely played Duke Nukem 3D. Installed the shareware demo in a PC magazine and played it but I was into Quake by then, plus I preferred Doom a lot more. Duke Nukem 3D art style never clicked with me, nor the main character, I guess --from the demo alone.

However, iirc people used to say that like Doom, Duke Nukem 3D wasn't a true 3D game. My friend showed me this video to prove his point that Duke Nukem 3D is indeed a 3D game and now I am doubtful:

He pointed at the 1:32 mark into the video where you can see a platform at the top, which is the end of the level.

He also pointed at the 6:20 mark when the main character crosses the platform to get to the end.

He told me that he flies below that platform and then flies above it using a jet pack when he plays. That platform and the way it is shown would be imposible to create in Doom.

I mentioned that the game is 2D, thought doubtful and he wasn't 100% sure either, but if they could build that platform and similar levels, the Duke Nukem 3D engine would be 3D indeed.

Dunno to be honest, I thought the first true 3D fps game of the era was Quake. That's how I remember people defined the game when it came out, circa late 1995 and 1996. I wonder whether my memory is failing me or not.

 

[HTupolev]

I have a 21 years old friend who told me today's morning that he learnt yesterday -contrary to what he thought his entire life- that Doom isn't a 3D game.

"Bridges and balconies" is a bizarrely arbitrary definition of "3D." Doom does have a z-axis with relevant gameplay effects. There are meaningful restrictions, but drawing a hard line and calling Doom "2D" is silly mid-90s marketing.

However, iirc people used to say that like Doom, Duke Nukem 3D wasn't a true 3D game. My friend showed me this video to prove his point that Duke Nukem 3D is indeed a 3D game and now I am doubtful:

Duke Nukem 3D basically works the same as Doom in that you can't build bridges and balconies with the core level geometry functionality.

However, there are walkable objects that can be placed on the map to create bridges and balconies.

 

[Allandor]

Is Duke Nukem 3D a true 3D game or a 2D game?

I have a 21 years old friend who told me today's morning that he learnt yesterday -contrary to what he thought his entire life- that Doom isn't a 3D game. Well, I always knew that I told him. I played around a lot with Doom editors and learnt many things about the engine, map creation and stuff. Everything was 2D, everything had a ceil and a floor.

I barely played Duke Nukem 3D. Installed the shareware demo in a PC magazine and played it but I was into Quake by then, plus I preferred Doom a lot more. Duke Nukem 3D art style never clicked with me, nor the main character, I guess --from the demo alone.

However, iirc people used to say that like Doom, Duke Nukem 3D wasn't a true 3D game. My friend showed me this video to prove his point that Duke Nukem 3D is indeed a 3D game and now I am doubtful:

He pointed at the 1:32 mark into the video where you can see a platform at the top, which is the end of the level.

He also pointed at the 6:20 mark when the main character crosses the platform to get to the end.

He told me that he flies below that platform and then flies above it using a jet pack when he plays. That platform and the way it is shown would be imposible to create in Doom.

I mentioned that the game is 2D, thought doubtful and he wasn't 100% sure either, but if they could build that platform and similar levels, the Duke Nukem 3D engine would be 3D indeed.

Dunno to be honest, I thought the first true 3D fps game of the era was Quake. That's how I remember people defined the game when it came out, circa late 1995 and 1996. I wonder whether my memory is failing me or not.

Quake was the first game that used a 3d terrain (well 3d levels) and 3d enemies. While Doom, Duke3d and many others used 2D Objekts for enemies, items etc.
Well I never fell in love with Quake 1, 3D characters were just not rendered as good as e.g. Duke 3d enemies (much more details). It really take them a while until the 3d characters looked better than old game 2d characters (but that's just my opinion).

 

[Sigfried1977]

just like in the previous post, I don't find anything noteworthy there, compared to Tekken Tag Tournament, the ground textures look much muddier and maybe only the characters look better. Was your point to show the characters details? Or the dragon head?

I think the characters look way better and so do most of the backgrounds. Sure, that wood paneling effect is very impressive, but Namco paid for it with a dojo that's adorned by a bunch of square, low poly pillars and a simple photo texture that's scrolling in the background. I'd agree that in some ways TTT looks a bit more advanced, but T5 does a much better job at balancing all the various effects. I remember we were all wowed when T5 came out back then.

Really unfortunate how back in the day, fighting games were pretty much the pinnacle in terms of visuals. (which makes sense considering all that's being rendered is two dudes and a very limited arena) Nowadays we usually hear remarks like "looking good for a fighting game".
I bought Tekken 7 on Friday. It looks fine, but it's not impressive by any stretch (and online is broken). Character models in particular have barely moved on from Tekken Tag 2. Faces in particular appear shockingly low poly during close-ups. Really humbling how UE4 continues to be trounced by its older sibling too, because shitty animations aside, Injustice 2 is a goddamned impressive looking title.

 

[Cyan]

"Bridges and balconies" is a bizarrely arbitrary definition of "3D." Doom does have a z-axis with relevant gameplay effects. There are meaningful restrictions, but drawing a hard line and calling Doom "2D" is silly mid-90s marketing.


Duke Nukem 3D basically works the same as Doom in that you can't build bridges and balconies with the core level geometry functionality.

However, there are walkable objects that can be placed on the map to create bridges and balconies.

Thanks for the insight, as usual. Why aren't those walkable objects in Duke Nukem 3D stackable? Could you stack them and create a perfectly convincing true 3D perception? Like playing a completely vertical level from platform to platform...

Quake was the first game that used a 3d terrain (well 3d levels) and 3d enemies. While Doom, Duke3d and many others used 2D Objekts for enemies, items etc.
Well I never fell in love with Quake 1, 3D characters were just not rendered as good as e.g. Duke 3d enemies (much more details). It really take them a while until the 3d characters looked better than old game 2d characters (but that's just my opinion).

Quake characters showed very few polygons, I remember. However, the true 3D feeling and the art style was praise-worthy. In fact it is a game with an odd art style that I've never seen ever after. Quake 2 and 3 kind of diverged from 1 and it's peculiar blend of medieval art mixed with something I can't describe.

 

[Cyan]

I think the characters look way better and so do most of the backgrounds. Sure, that wood paneling effect is very impressive, but Namco paid for it with a dojo that's adorned by a bunch of square, low poly pillars and a simple photo texture that's scrolling in the background. I'd agree that in some ways TTT looks a bit more advanced, but T5 does a much better job at balancing all the various effects. I remember we were all wowed when T5 came out back then.

Really unfortunate how back in the day, fighting games were pretty much the pinnacle in terms of visuals. (which makes sense considering all that's being rendered is two dudes and a very limited arena) Nowadays we usually hear remarks like "looking good for a fighting game".
I bought Tekken 7 on Friday. It looks fine, but it's not impressive by any stretch (and online is broken). Character models in particular have barely moved on from Tekken Tag 2. Faces in particular appear shockingly low poly during close-ups. Really humbling how UE4 continues to be trounced by its older sibling too, because shitty animations aside, Injustice 2 is a goddamned impressive looking title.

Tekken 7 is a strange case. I don't see why the game is running at such a low resolution on the Xbox One, for instance. Wonder where they spend the resources..,heck, it's a fight game. Or maybe that's a case of spending the resources on lots of techniques we don't know of, but you see it in motion and it looks like your everyday's life game.

Maybe it's just me. As for Tekken Tag Tournament, it sounds like one of those cases where the machine was recently launched and developers believed it had almost infinite power in their hands. Had that feeling with games like Perfect Dark X360. I didn't see textures like those in any X360 game from then on. Ryse is another game that I didn't see equaled on the XB1, despite the fact that it is a launch game.

Eventually developers seem to add features as if they were checkboxes but not all of them offer tangible benefits depending on the game.

 

[Nesh]

I think the characters look way better and so do most of the backgrounds. Sure, that wood paneling effect is very impressive, but Namco paid for it with a dojo that's adorned by a bunch of square, low poly pillars and a simple photo texture that's scrolling in the background. I'd agree that in some ways TTT looks a bit more advanced, but T5 does a much better job at balancing all the various effects. I remember we were all wowed when T5 came out back then.
.

That specific stage just happened to be "simpler". Namco didnt exactly pay for. The Dojo just worked as it was. It was just an artistic choice. TTT's only downside were the animations which were taken directly from the PS1/Arcade games and stick out like a sore thump in motion. (btw looks like the TTT video is either PAL or it is running badly on emulation)
It just went downward and lets not forget that TTT was almost a launch game. You would think that we would only see better graphics from there, a clean improvement like we did with PS1 considering also that PS2 was a peculiar pieace of hardware that came with atrocious documentation and tools at the beginning. In T5 it looks like like they sacrificed everything TTT was doing right to accommodate easier for the roaming environmnents. And even then T4 had larger roaming environments that in some cases had better materials too..
Soul Calibur 3 on the other hand looked significantly more impressive than 5.

 

[bunge]

Holy crap I went down a forum wormhole last night. Wolfenstein 3D for the Sega Genesis is amazing.

Sorry if this is the wrong thread.