Before you start
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Porting maps from Goldsrc to Source is not easy. Depending on the complexity of the map, be prepared to invest anywhere from 3 to 50+ hours into a single port. Prior experience with Valve’s Hammer Editor is helpful, however porting maps is entirely doable without ever having used Hammer before.
This guide was primarily written in July of 2025. There is a small number of people who occasionally work on tools for the GoldSrc porting process, so depending on when you are reading this there may be some new ways to make the process easier. Search the web or ask in the Momentum Mod Discord and you might find something useful.
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Before you start, you should know that maps with simple geometry work best for porting. Complex geometry can cause invalid solids as vertices tend to shift around if they are off grid, and you will be forced to recreate a lot of the brushes manually. Patches and props cannot be ported across either, so choose maps without those or you will have to spend a lot of time manually replacing them in Hammer.
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Ammo System
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All Defrag weapons, the RJ Rocket Launcher, the Sticky Bomb Launcher, and Concs can be controlled with separate ammo types.
By default players have infinite ammo.
Additionally, an ammo limit can be set that doesn’t allow the player to have more than a certain amount.
By default, the player has a limit of 200 on the maximum amount of ammo they can carry of any type.
This can be changed with the SetAmmoLimit input, where a limit of -1 means no limit.
The ammo limit does not prevent the player from carrying infinite ammo, it only applies when the player’s ammo is finite.
Pickup Entities
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In order to create an ammo pickup use momentum_pickup_ammo entity.
The key AmmoName controls the type of ammo. It takes a string which is one of the names in the table below.
The entity also takes a PickupAmmo key which controls how much ammo the player gets.
momentum_weapon_spawner entity can also give ammo on pickup, controlled by the PickupAmmo key.
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This page covers Momentum Mod’s implementation of world portals, how they work, how to add them into a map, as well as the limitations associated with the technology.
Prerequisites
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In order to easily follow along with this guide it is recommended to have the following:
- A basic knowledge of the Hammer editor and how to create functional, playable maps using it
- A version of Momentum Mod from version 0.8.8 or onwards
- The
momentum.fgd file in your Hammer configuration
Introduction
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What Are Portals?
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World portals are placeable entities that emulate a connection between two points, such as the example pictured below. Portals can have many uses for mappers attempting to push their creativity or for those stuck in Hammer-related corners.
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