Star Fox 64 PSP port is now playable start to finish, developer writes

A solo developer's progress report on porting Star Fox 64 to PSP details a graphics rewrite, a week-long fog bug and a first-of-its-kind use of the PSP's second CPU for audio.

AI-drafted from 2 sources. This story was written with AI from the outside reporting listed under Sources, and checked by automated tools before it went up. The originals have the full detail.

A developer working on a Star Fox 64 port for the PSP says the game is now playable from start to finish, complete with sound and widescreen support. The claim comes from Daniel Welch, known online as TheMrIron2, in a progress report published on KOMSTATION and shared on the r/retrogamedev thread. Welch has been working on the project since May, and the piece is less a launch announcement than a technical diary of what it takes to move a Nintendo 64 game onto Sony's ageing handheld.

Porting between two systems from roughly the same console generation sounds simpler than it is. The N64 and PSP have very different graphics pipelines, and Welch's port currently runs the N64's graphics commands through PSPGL, an OpenGL-style layer for the PSP, before they reach the console's actual GPU (called the GE). That is, as Welch puts it, effectively a double translation: N64 code becomes PSP-friendly instructions, which get translated to OpenGL, which then get translated back into something the GE understands. Star Fox 64 does not make this easy. It favours lots of small, frequent draw calls, the opposite of what the PSP's hardware prefers, which is fewer, larger batches. Welch plans to bypass PSPGL entirely and write directly against the GE using PSP's lower-level graphics interface, which should cut CPU overhead and open up optimisations that are not possible through the current middle layer.

The fog bug that took a week to solve

The report walks through one especially stubborn issue: getting hardware fog to behave the same way on PSP as it does on N64, since the two consoles implement it differently. A separate, related bug affected a specific pre-title cutscene shot of the Arwing, where the camera moved into the ship without clipping on N64 but did clip on PSP. Welch says a contributor called z2442 suggested the fix: an incorrectly imported near clipping value, carried over from the Starship PC port, needed to be changed from 10 to 2. Welch notes drily that fixing this bug did not fix the fog problem, which suggests these two issues, though tangled together in the debugging process, were unrelated.

A second chip nobody else has used for sound this way

Performance figures given in the report show the game holding a firm 30 frames per second with sound disabled, but dropping when audio is active, with the title screen falling to 15 frames per second during a fanfare that uses many audio voices at once. To claw some of that back, Welch is offloading audio work to the PSP's Media Engine, a secondary chip, and specifically to a component within it called the Virtual Mobile Engine (VME), normally used for multimedia decoding. Welch describes this as the first PSP port to attempt VME-based sound processing, currently limited to one audio effect (ENVMIXER) because data transfer overhead eats into the VME's speed advantage. There are ambitions to also decode ADPCM audio compression on the VME, which Welch expects would meaningfully improve performance further. One complication: this approach has no equivalent on PS Vita, where Media Engine access is limited to a fixed set of behaviours built into the system, meaning custom code such as this cannot run there at all. A PS Vita fallback without Media Engine support is described as a later task, and PPSSPP, the PSP emulator, does not currently support Media Engine sound either.

What is still open

Beyond the port itself, Welch is building a reusable library called n64psp, intended to share code such as maths routines and display setup across future N64-to-PSP ports, with the suggestion that existing efforts like Super Mario 64 and Perfect Dark ports could benefit retroactively. Local wireless multiplayer, a fixture of the original Star Fox 64, is also under investigation but unconfirmed. No release date is given, and Welch is explicit that further months of refinement are planned before anything resembling a public build appears.

Sources

• I wrote an article on my work porting Star Fox 64 to PSP! (KOMSTATION)
• Discussion: I wrote an article on my work porting Star Fox 64 to PSP! (Reddit)

Image: KOMSTATION