Grand Prix 2 & IndyCar Racing 2 Forums

Hi,

releasing a new Jam Editor - big advantage for GP2 is built in palette generation for JAMs that require it.

Big caveat; some JAMs do not need it and may even crash GP2 - horizon JAMs for example.

This is over a year's on/off development in spare time, it feels generally stable but as ever without multiple tests hard to find bugs, so please let me know of any issues, plus step-by-step instructions leading up to the issue. I can then investigate.

https://github.com/jamesknopp/GPxJamEdi ... tag/v1.0.1

Please have a play and enjoy.

Cheers
Jim

jamesknopp wrote: Sat Jun 27, 2026 5:39 pm Hi,

releasing a new Jam Editor - big advantage for GP2 is built in palette generation for JAMs that require it.

Big caveat; some JAMs do not need it and may even crash GP2 - horizon JAMs for example.

This is over a year's on/off development in spare time, it feels generally stable but as ever without multiple tests hard to find bugs, so please let me know of any issues, plus step-by-step instructions leading up to the issue. I can then investigate.

https://github.com/jamesknopp/GPxJamEdi ... tag/v1.0.1

Please have a play and enjoy.

Cheers
Jim

Thank you for spending time on it. Do we have any clues yet on what all of the jam unknowns were on the original editor? I'm wondering if you want to attack that with your new editor.

So I have a Jam Analysis window which displays all the flags to see what utilised what. My notes so far on it:

Flag 1 - car shadow, gp2 only
Flag 2 - helmet gp2... gp3 sprite pit crew, helmet gp3 hwjam,
Flag 3 - RCR related
Flag 4 - transparency
Flag 5 & 6 aka Multi-Part Texture seen on helmets, car liveries and car items. DSH1,2,3 has flag 6 only. Assume it enables 'specular shading'
Flag 7 - unused gp3 hw, gp3 sw & gp2. GP3 -SW Flagman. Pitprop
Flag 8 - GP3: DSH1,2,3. Horizons, Front JackMan gp3. Marsall push. Steering wheel. Smoke. Cockpit upper. ARM64. //no palettes
Flag 9 - GP3 HW VSusp. Horizons. Helmets, chassis. Used in a lot of transparent elements. But not used in some others? // non standard size (power of 2)
Flag 10 - GP3 HW used in sprites/transparent elements // non standard size (power of 2)
Flag 11 - spgrid smoke? same in gp2 and gp3 (blending??) - enables additive blending on smoke
Flag 12 - not used
Flag 13 - used a lot in GP3. Not in GP2, unknown.
Flag 14 - used on tarbump3
Flag 15 & 16 unused in GP3, unknown

There's some scaling flags and info which I've yet to uncover rationale for, but a lot are used on the trees, smoke sprites. I'll need to dig into the ASM more.