I don't get why they are always talking about the 2013 aspect of the game in comparison with the final product. CDPR said it several times, they decided to change the whole rendering process, i'm okay with it, its their choice. I was already pretty sceptical about the old build. It looked way to beautiful in comparison of what we were used to see. But then, what happened to the E3 2014 graphics, or just a few weeks after it, the 35 minutes gameplay demo? We can cleary see that the game was pretty similar with what we have now, but at the same time very different. It had so many more details, the atmosphere was better (colors, water) and they were more details in general. It looked like the walls had tesselation (which we dont have in the final product on PC), the draw distance was better, etc.
What happened to that game, what we could saw just a few months ago ?
EDIT : The 35 min footage is the reason I was upset about the finals graphics of the game, like many other gamers that have a good PC to run a game smoothly. 35 minutes is a long footage, I thought : "Well looks like the final product isnt gonna be very different from what we've seen in this long demo", and then, in January 2015, they were these trailers released with a game what had totally changed. But dont get me wrong, I've already played a lot of hours, and I love this game, it would have been a perfect game if it looked like it did in the long footage.
Please apologize my bad english, I hope I was clear enough

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I'm not judging you on what you say. Everyone has his own opinion on the subject.
The thing is, here, CD Projekt RED is releasing an open-world RPG released on next-gen consoles and PC. First of all, imo, I've been seeing alot of discussions about new games being not what they were hyped for, mainly trailers where amazing graphics are showcased, and in the end you get a pale version of the trailer. I can quote Watch_Dogs/Most recent Ubisoft games, which were messy in a point where I barely touched them. And the controversial topics on the Internet for some recent games also, many dramas, etc. I'm gonna summarize quickly the subject with Ubisoft case.
For Watch_Dogs the downgrade was real. The game was bugged to hell, the hype was real, and the graphics were pushed all the way down to support old consoles (360 and PS3), with a port to PC a little bit messy. It was sterile, and the E3 trailer hype, where the real potential was, the retail version didn't. No sunshafts, lighting renderer toned down, and a more less particles (the nightclub was... lol).
AS: Unity, well, if you've been on the Internet recently, you can watch Youtube videos, they speak for themselves. The game port is horrible, it's an absolute mess. I get 20fps with an 4670k and a 280x (it should run a lot better). And the bugs made the game unplayable, I couldn't finish the prologue without falling through the map.
Second of it, I cannot tell what they did exactly, I'm not part of CDPR. But you can think of many ideas why things here and there aren't anymore. Here's mine on what you said.
For the colors, it's mainly the art direction. The first trailers were gray-ish with sharpen effects (which they said was horrible to play after a while iirc), I think they wanted more life on screen, hence the saturation and texture changes to more colorful materials.
For the details, I saw the comparison with Novigrad walls (before/after stuff). It's not tesselation from what I've seen. It's mostly meshes (3D objects) placed so the wall looked like a wall with bricks etc. My guess would be that in order to run the game properly on every platforms, the meshes had to be scrapped. Less polygons, less shadows, more frames, that kind of stuff. IIRC, there were some boats also on the right of the entrance we saw in the 35 minutes footage. I guess those meshes were "too much" to render and to get the framerate they wanted us to have, they maybe had to delete them.
To the first point, CDPR was, "lynched". People are sceptical with what publishers are showing to us. And it can be quick today. A post on NeoGaf, Reddit, Twitter, and the information's now spreading quickly with non-sense or false facts, and you have the Witcher 3 drama. People were yelling "CDPR the new Ubisoft/EA", etc etc. People never played the game, and still yelled their opinion on a topic they didn't understood. There's also people, I saw that alot on forums, and it's kinda weird, who wants the game to fail, in order to prove a point. "Told you guys, it was gonna fail", that thing was common on games forums those last days.
The CDPR staff was flooded with that mass of complains. When you're in the final days before a release like that, that's the last thing you'd like to see on the Internet forums. I hope their spirit was ready for that. I genuinely like CDPR, and their staff is amazing, for the interviews, the time spent talking with us, it matters. I hope they were ready for that, and that the sales will support them to the point where we'll see Cyberpunk 2077 released one day.
The second point, though more technical, is important. I can only guess, I'm not a technical engineer. The state of a game can change from A to Z through the game development.
The lack of communication from CDPR on the subject, by that I mean our discovery that "You're not gonna have the 2013 experience, because X or Y", it's hard to announce that. The game is amazing, you don't want people to get pissed off because : you know you're making the game playable, but they won't get it why. You can't tell people that you changed the engine rendering technique, that you implemented the game rules, the AI, the particles effects, the characters,the assets, and so the data-streaming rate could load all of this in this giant world, and all the things that make it a game. That's what meant the founders of CDPR by "but actually there's plenty of things that improved since 2013". In 2013, we saw not even 1% of the game, we saw roughly 20 scenes where they showcased us their vision of the game. But by the end of 2014, some gameplay footages were shown, and their new techniques were up, the game was close from what we can now play today.
I'm an amateur game developer, I'm prototyping stuff with Unity3D, I cannot say I'm the best expert on this subject, maybe I'm wrong, but there's so many things behind the scenes that are not shown for developing a video game. It's not magic, there's work behind it. To add the wall mesh, if something's deleted, there's always a reason behind it. They're not deleting details for the "lulz"
Damn, I wrote a book right there.