Hitscan

For a more technical article on this topic, see TraceLines.

Half-Life 2 has many hitscan weapons (weapons which don't actually fire bullets, but instead trace a line and spawn an explosion/damage at the end). Sometimes it is useful, however, to hitscan just to find where a line hits a wall/player/etc. So I took some code from CBaseEntity::FireBullets() to create CBaseEntity::HitScan(). I put the following code into baseentity_shared.ccp.

Vector CBaseEntity::HitScan( const FireBulletsInfo_t &info, unsigned int mask )
{
	trace_t tr;
	CTraceFilterSkipTwoEntities traceFilter( this, info.m_pAdditionalIgnoreEnt, COLLISION_GROUP_NONE );
	Vector vecEnd = info.m_vecSrc + info.m_vecDirShooting * info.m_flDistance;
	AI_TraceLine(info.m_vecSrc, vecEnd, mask, &traceFilter, &tr);
	return tr.endpos;
}

and the definition into BaseEntity.h.

	virtual Vector			HitScan( const FireBulletsInfo_t &info, unsigned int mask );

This function can easily be adapted to take line definitions in other formats. Simply have it generate the FireBulletsInfo_t structure given a start and end or start and direction.