[Max_R]

Originariamente inviato da Dark_Lord

Idem, non 8 volte, ma un 3 volte sicuro dal 2006, per l'epoca era veramente tanto avanti, anche con i portali etc, ora rigiocarlo adesso si vede che ha perso un po' del suo smalto, ma resta figo

I portali sono stati usati molto meno del previsto, ma erano stati teorizzati fin dalle prime stesure del gioco, nel 96
Credo che abbia influenzato anche il Portal di Valve

2.4 What is Portal Technology?
--------------------------------

A new technology, Portal Technology is the key to Prey's engine.
This technology allows environments and events to take place that would be
impossible in real life, or by Geometry Laws as we know it.

Other 3D Engines like Quake use BSP (Binary Space Partitioning)
trees. Portal Technology is differs from BSP in a few ways.


* What Paul Schuytema says about Portal Technology:

"What the portal technology gives us, is the ability to break free from
static environment geometry-our environments can change geometry dynamically,
during game play, in a far more interesting manner than simply opening doors
and moving platforms that are found in most BSP-based engines."

* An article in Boot Magazine interviewing Joe Gilby about Portal Technology:

In portal games, the world is made of connected convex polyhedrons with
polygons allowing visibility between the polyhedron cells. "The idea is that
these cells are stored in a graph structure such that, when traversed, they
will sort correctly," explains Joe Gilby. "If you're in a room with an open
door into another room (all different portals), the far rooms are drawn first
but just the pieces that are visible through the door and window are actually
rendered. The cells subdivide the world into pieces that quickly identify
areas that are of interest, and the objects which exist in those cells. Portal
supports arbitrary sloping surfaces, and six-degrees-of-freedom viewing"

One advantage of this approach is the flexibility of defining the portal cells.
Current BSP implementations require splitting polygons that straddle the
extended plane of other polygons, so the more complicated the scene, the
more polygons you have to deal with. Portals require splitting in order to
maintain polyhedron convexity, but it's local to the immediate neighborhood
and can be avoided by level designers, given a little training. This allows for
more complicated settings. Also, the portal cell based approach can avoid
screwing affects such as characters and explosions piercing through walls,
due to the portal cell drawing order. In a BSP renderer, the physics have to
prevent objects in one leaf penetrating into another or clipping, because the
renderer will dutifully draw them in both.

"In portal, objects are confined to their containing cell, unless you explicitly
say otherwise," says Gilby. "This makes the superpostitioning come out right.
We can also use portal cells to define open spaces containing an atmosphere
medium, such as flowering water, billowing smoke, and murky water."


2.5 How does the Prey Engine compare to...?
---------------------------------------------

|Feature | Prey | Quake II | Unreal | DirectEngine |
__________________________________________________ ___________________________
|True 3D | YES | YES | YES | YES |
|Hardware Only | YES | NO | NO | NO |
|API |Own/OGL| OpenGL |D3D/Glide| Direct3D |
|Color Depth | 16Bit | 8Bit | 16Bit | 16Bit |
|Engine Type | PT | BSP | BSP | BSP |
|Radiosity | YES | YES | NO | NO |
|MMX Support | NO | NO | YES | NO |

PT = Portal Technology
BSP = Binary Space Partitioning
D3D = Direct3D

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