gistfile1.cpp

/*
 * This plugin alters view punch to better reflect the recoil that's actually
 * applied. The problem is that viewpunch is linearly proportionate to the
 * increase in recoil velocity, but a higher velocity also means the recoil will
 * increase for a longer time and take longer to decay. This plugin modifies
 * viewpunch to increase exponentially with recoil velocity increase.
 */
#include "util.h"
#include "plugin.h"
#include <stdexcept>

ConVar view_punch_pct("view_punch_pct", "0.0015");
ConVar view_punch_exp("view_punch_exp", "2");

/**
 * custom_kickback - Update player aimpunch velocity and viewpunch after a shot
 * @player:	Player to update for
 * @angle:	Recoil angle
 * @magnitude:	Recoil velocity increase
 *
 * Use the cos and sin of angle multiplied by magnitude to determine the
 * components to be subtracted from the aim punch velocity, then do the same but
 * with magnitude taken to a certain power and certain factor determined by
 * cvars and subtract that from viewpunch.
 */
static void custom_kickback(
		const char *player,
		const float angle,
		const float magnitude)
{
	const auto x = cosf(angle * M_PI_F / 180.f);
	const auto y = sinf(angle * M_PI_F / 180.f);

	auto *aim_punch_vel = (QAngle*)(player + 0x9A4);
	auto *view_punch = (QAngle*)(player + 0x98C);

	aim_punch_vel->x -= x * magnitude;
	aim_punch_vel->y -= y * magnitude;

	const auto view_punch_factor =
			powf(magnitude, view_punch_exp.GetFloat()) *
			view_punch_pct.GetFloat();

	view_punch->x -= x * view_punch_factor;
	view_punch->y -= y * view_punch_factor;
}

/**
 * hook_KickBack - C_CSPlayer::KickBack hook
 * @ecx:	Player pointer
 * @xmm1:	Recoil angle
 * @xmm2:	Recoil velocity increase
 *
 * Assembly wrapper to pass the player pointer, recoil angle and recoil
 * magnitude to custom KickBack function
 */
__declspec(naked) static void hook_KickBack()
{
	_asm {
		sub esp, 8
		movss dword ptr [esp + 4], xmm2
		movss dword ptr [esp], xmm1
		push ecx
		call custom_kickback
		add esp, 12

		retn
	}
}

/**
 * plugin::Load - Valve plugin load method override
 * @interfaceFactory:	engine.dll factory
 * @gameServerFactory:	server.dll factory
 *
 * Detour C_CSPlayer::KickBack for custom view punch
 */
bool plugin::Load(
		CreateInterfaceFn interfaceFactory,
		CreateInterfaceFn gameServerFactory)
{
	ConnectTier1Libraries(&interfaceFactory, 1);
	ConnectTier2Libraries(&interfaceFactory, 1);
	ConVar_Register(0);

	uintptr_t start, end;
	get_module_bounds("server.dll", &start, &end);

	uintptr_t KickBack; // C_CSPlayer::KickBack
	try {
		const auto *KickBack_sig = "\x83\xEC\x24\x0F\x28\xC1";
		const auto *KickBack_mask = "xxxxxx";
		KickBack = sigscan(
				start,
				end,
				KickBack_sig,
				KickBack_mask) - 3;
	} catch(...) {
		Error("Sigscans failed!\n");
		return false;
	}

	patch_jmp_rel32(KickBack, hook_KickBack);

	return true;
}

/**
 * plugin::Unload - Valve plugin unload method override
 *
 * Unregister the ICVar and disconnect libraries
 */
void plugin::Unload()
{
	ConVar_Unregister();
	DisconnectTier2Libraries();
	DisconnectTier1Libraries();
}