Okay, so I've compiled a lot of different shots from Halo: CE, Halo 2, Halo 3, and Halo 4. I haven't included Halo 5 , as I remember it being said that that Halo 5 was "better" in terms of design. The original graphics were used for Halo: CE and Halo 2, so as to represent the designs in their original form.
On the outside, a lot of Forerunner architecture seems quite similar. Angles and slants are present in all designs, with multiple segments and illuminated areas. Repetition of designs is something that is present in practically all architecture, though something I'm not counting is a repetition of textures as a result of low-graphics design. (e.g. the walls of the Threshold Mine in Halo 2). While Halo 4 is able to fit in more detail, it doesn't deviate too far away from the use of angled edges. Light schemes (while more present) still follow the same relative pattern of light blue, and even the orange colors used for Promethean structures are the same as when a Monitor or Sentinel attack - indicating aggression, which is the role of Prometheans. A lot of the difference seem to be the textures of the various structures; Halo: CE - Halo 3 has Forerunner structures that look more like concrete than metal, giving it an "aged" look. Current Forerunner materials, though, don't deviate far enough to be considered a grievous error, as they're closer to that of 343 Guilty Spark
. Aesthetically, this conveys a more "living" feel to not just the architecture itself, but to the Forerunner culture as a whole, which is narratively the case with the Domain reemerging with Forerunner remnants.
Structures on Installation 04Threshold Gas MineThe Cartographer on Installation 00Tower facility on Installation 00Branch of Installation 00, showing vast illuminationsTower structures on RequiemDistant facility on RequiemStructure on RequiemStructure baseRamp up to Structure interiorDoor: Requiem StructureDoor on Installation 04Threshold Gas Mine doorDoor on Installation 08Exterior walls of Transit Structure on Requiem
The interiors of Forerunner buildings certainly has seen a progression of detail, but I don't think it's any greater of a leap than from Halo 2 to Halo 3. There's a change in the "material", but overall there's still platforms supported by light (or just a gondola a la
Delta Halo) and the use of angled sections and slopes. The pictures that I took are from the Insider Flight, so the lights in Halo 4 are a bit intense, but overall I think they fit the vibe from both Halo: CE and Halo 3 in that there are interiors with overall gloomy darkness, and then areas where it's well-lit. The lights are a different design, but overall the interiors of Halo 4 are no more or less lit than those in past Halos.
Interior lightbridge, Installation 04Entryway to tower, Installation 00Interior of tower, Installation 00Interior, Cartographer, Installation 00Elevator (note the energy-beam suspension), Installation 00Interior hallway, RequiemInterior, transit facility, RequiemElevator, Requiem (similar to the elevator on Installation 00)Interior, tower, Requiem
Overall, and I might have said this above, I think the biggest difference is the material depicted (surface texture), and the level of detail allowed through the progression of the Xbox's technology. The Forerunner aesthetic retains the same slants and angles, with a few curves here and there - rather than, for example, suddenly becoming smooth and exclusively curved like Covenant architecture - and has the same basic principles of "grey metal and blue or orange lights" that's been present since Halo 2.