How to fix sliding/surfing from slope surface in Quake
Author: kleskbyAs you could notice while playing quake, if you stand on a slope you slowly move down the slope. This is very annoying player physics bug in Quake 1.
Solution 1.
Open client.qc, at the bottom of PlayerPreThink add the following code:
if(self.movetype != MOVETYPE_NOCLIP && clienttype(self) != CLIENTTYPE_BOT) //SLIDING (SURFING) FIX
{
if(self.flags & FL_ONGROUND && vlen(self.velocity) < 30)
{
traceline (self.origin, self.origin - '0 0 42', TRUE, self); //detecting slope angle
if(trace_fraction > 0.65) self.movetype = MOVETYPE_BOUNCE;
else self.movetype = MOVETYPE_WALK;
}
else self.movetype = MOVETYPE_WALK;
}
The function checks if the player is not in noclip mode and is not a bot, then it checks if the player is on the ground (FL_ONGROUND flag is set) and has a velocity less than 30. If both conditions are met, the code checks the angle of the ground the player is standing on by performing a traceline from the player's current position to a point just below them. The TRUE parameter indicates that the trace should stop when it hits a solid surface.
If the trace_fraction (which is the fraction of the trace line that was traveled before hitting a solid surface) is greater than 0.65, the player's movement type is set to MOVETYPE_BOUNCE (can be other movetype). Otherwise, returning player movement type to a normal state.
Solution 2.
If you use modern source port such as DarkPlaces or FTEQW you can recode player movement function by defining SV_PlayerPhysics. Here is an example how to do this:
float lastclientthink;
float sv_accelerate;
float sv_maxairspeed;
float sv_friction;
float sv_maxspeed;
float sv_stopspeed;
float sv_gravity;
.float ladder_time;
.entity ladder_entity;
.float gravity;
void() SV_PlayerPhysics =
{
local vector wishvel, wishdir, v;
local float wishspeed, f;
// this is the first function run each frame, so do bot think here
if (clienttype(self) == CLIENTTYPE_BOT)
if (self.movetype == MOVETYPE_NONE)
return;
if (time != lastclientthink)
{
lastclientthink = time;
sv_maxairspeed = cvar("sv_maxairspeed");
sv_maxspeed = cvar("sv_maxspeed");
sv_friction = cvar("sv_friction");
sv_accelerate = cvar("sv_accelerate");
sv_stopspeed = cvar("sv_stopspeed");
sv_gravity = cvar("sv_gravity");
}
if (self.punchangle != '0 0 0')
{
f = vlen(self.punchangle) - 10 * frametime;
if (f > 0)
self.punchangle = normalize(self.punchangle) * f;
else
self.punchangle = '0 0 0';
}
if (self.punchvector != '0 0 0')
{
f = vlen(self.punchvector) - 30 * frametime;
if (f > 0)
self.punchvector = normalize(self.punchvector) * f;
else
self.punchvector = '0 0 0';
}
// if dead, behave differently
if (self.deadflag)
return;
if (!self.fixangle)
{
// show 1/3 the pitch angle and all the roll angle
// LordHavoc: no real interest in porting V_CalcRoll
//self.angles_z = V_CalcRoll (self.angles, self.velocity)*4;
self.angles_x = 0;
self.angles_y = self.v_angle_y + self.punchangle_y;
self.angles_z = 0;
}
if (self.flags & FL_WATERJUMP )
{
self.velocity_x = self.movedir_x;
self.velocity_y = self.movedir_y;
if (time > self.teleport_time || self.waterlevel == 0)
{
self.flags = self.flags - (self.flags & FL_WATERJUMP);
self.teleport_time = 0;
}
}
else if (self.movetype == MOVETYPE_NOCLIP || self.movetype == MOVETYPE_FLY)
{
// noclipping or flying
self.velocity = self.velocity * (1 - frametime * sv_friction);
makevectors(self.v_angle);
//wishvel = v_forward * self.movement_x + v_right * self.movement_y + v_up * self.movement_z;
wishvel = v_forward * self.movement_x + v_right * self.movement_y + '0 0 1' * self.movement_z;
// acceleration
wishdir = normalize(wishvel);
wishspeed = vlen(wishvel);
if (wishspeed > sv_maxspeed)
wishspeed = sv_maxspeed;
if (time >= self.teleport_time)
{
f = wishspeed - (self.velocity * wishdir);
if (f > 0)
self.velocity = self.velocity + wishdir * min(f, sv_accelerate * frametime * wishspeed);
}
}
else if (self.waterlevel >= 2)
{
// swimming
makevectors(self.v_angle);
//wishvel = v_forward * self.movement_x + v_right * self.movement_y + v_up * self.movement_z;
wishvel = v_forward * self.movement_x + v_right * self.movement_y + '0 0 1' * self.movement_z;
if (wishvel == '0 0 0')
wishvel = '0 0 -60'; // drift towards bottom
wishdir = normalize(wishvel);
wishspeed = vlen(wishvel);
if (wishspeed > sv_maxspeed)
wishspeed = sv_maxspeed;
wishspeed = wishspeed * 0.7;
// water friction
self.velocity = self.velocity * (1 - frametime * sv_friction);
// water acceleration
f = wishspeed - (self.velocity * wishdir);
if (f > 0)
self.velocity = self.velocity + wishdir * min(f, sv_accelerate * frametime * wishspeed);
}
else if (time < self.ladder_time)
{
// on a func_ladder or swimming in func_water
self.velocity = self.velocity * (1 - frametime * sv_friction);
makevectors(self.v_angle);
//wishvel = v_forward * self.movement_x + v_right * self.movement_y + v_up * self.movement_z;
wishvel = v_forward * self.movement_x + v_right * self.movement_y + '0 0 1' * self.movement_z;
if (self.gravity)
self.velocity_z = self.velocity_z + self.gravity * sv_gravity * frametime;
else
self.velocity_z = self.velocity_z + sv_gravity * frametime;
if (self.ladder_entity.classname == "func_water")
{
f = vlen(wishvel);
if (f > self.ladder_entity.speed)
wishvel = wishvel * (self.ladder_entity.speed / f);
self.watertype = self.ladder_entity.skin;
f = self.ladder_entity.origin_z + self.ladder_entity.maxs_z;
if ((self.origin_z + self.view_ofs_z) < f)
self.waterlevel = 3;
else if ((self.origin_z + (self.mins_z + self.maxs_z) * 0.5) < f)
self.waterlevel = 2;
else if ((self.origin_z + self.mins_z + 1) < f)
self.waterlevel = 1;
else
{
self.waterlevel = 0;
self.watertype = CONTENT_EMPTY;
}
}
// acceleration
wishdir = normalize(wishvel);
wishspeed = vlen(wishvel);
if (wishspeed > sv_maxspeed)
wishspeed = sv_maxspeed;
if (time >= self.teleport_time)
{
f = wishspeed - (self.velocity * wishdir);
if (f > 0)
self.velocity = self.velocity + wishdir * min(f, sv_accelerate * frametime * wishspeed);
}
}
else if (self.flags & FL_ONGROUND)
{
// walking
makevectors(self.v_angle_y * '0 1 0');
wishvel = v_forward * self.movement_x + v_right * self.movement_y;
// friction
if (self.velocity_x || self.velocity_y)
{
v = self.velocity;
v_z = 0;
f = vlen(v);
if (f < sv_stopspeed)
f = 1 - frametime * (sv_stopspeed / f) * sv_friction;
else
f = 1 - frametime * sv_friction;
if (f > 0)
self.velocity = self.velocity * f;
else
self.velocity = '0 0 0';
}
// acceleration
wishdir = normalize(wishvel);
wishspeed = vlen(wishvel);
if (wishspeed > sv_maxspeed)
wishspeed = sv_maxspeed;
if (time >= self.teleport_time)
{
f = wishspeed - (self.velocity * wishdir);
if (f > 0)
self.velocity = self.velocity + wishdir * min(f, sv_accelerate * frametime * wishspeed);
}
}
else
{
// airborn
makevectors(self.v_angle_y * '0 1 0');
wishvel = v_forward * self.movement_x + v_right * self.movement_y;
// acceleration
wishdir = normalize(wishvel);
wishspeed = vlen(wishvel);
if (wishspeed > sv_maxairspeed)
wishspeed = sv_maxairspeed;
if (time >= self.teleport_time)
{
f = wishspeed - (self.velocity * wishdir);
if (f > 0)
self.velocity = self.velocity + wishdir * min(f, sv_accelerate * frametime * wishspeed);
}
}
};
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