Those expecting confirmation of a downgrade to Marvel’s Spider-Man when assessing final code should probably look away now. Having stacked up the final game against the E3 2017 presentation, our overall conclusion is that Insomniac is on the money here – there have been changes, as there are during production of any game – but there has been no technical downgrade. In fact, we’d say that the final presentation is upgraded in key respects, both technical and artistic.
We’ll begin by tackling the key change that kicked off the whole episode – an adjustment in puddle placement in a scene which sees far less water coverage. It’s the first image in the screenshot comparison block below, and there’s no denying that the impact of the E3 2017 image is more striking. But what’s more interesting is the composition of reflections in the water itself. Insomniac’s Spider-Man uses reflections extensively – and brilliantly – throughout the game, and in the demo, these are rendered using a combination of screen-space and cube-map reflections.
Screen-space reflections are exactly that – elements of the scene that are visible can be repurposed and mapped onto reflective surfaces to convincing effect, but the key limitation is that parts of the scene that should be reflected but aren’t rendered can’t be included. For this eventuality, there is a fallback – the cube-map reflection. Think of cube-maps as static, pre-generated snapshots of the scene. The E3 demo uses tight, scene-specific cube-maps and SSR in tandem to give an effect so convincing that many even considered that Spider-Man may be using ray-tracing – but that isn’t the case.
Source: Eurogamer Debunking the Spider-Man 'downgrade'