/* Copyright (C) Tom Scutt and Core Design Ltd, 2001.
* All rights reserved worldwide.
*
* This software is provided "as is" without express or implied
* warranties. You may freely copy and compile this source into
* applications you distribute provided that the copyright text
* below is included in the resulting source code, for example:
* "Portions Copyright (C) Tom Scutt and Core Design Ltd, 2001"
*/
// Swarm update. (Code reproduced by kind permission of Core Design Ltd.)
void UpdateAgents()
{
AGENT_STRUCT *agent;
long h, i, angle, dx, dy, dz, oldx, oldy, oldz;
agent = &agents[0];
for (i=0;i<MAX_AGENTS;i++,agent++)
{
//for each agent, check to see if it's active
if (agent->active)
{
//remember its current position
oldx = agent->xpos;
oldy = agent->ypos;
oldz = agent->zpos;
//update x and z pos depending on y-rotation and speed
agent->xpos += agent->speed * SIN(agent->yrot);
agent->zpos += agent->speed * COS(agent->yrot);
//update y depending on fallspeed
agent->ypos += agent->fallspeed;
//update fallspeed by adding gravity
agent->fallspeed += GRAVITY;
//calculate the difference between the agent's
//position and the target position
dz = target->zpos - agent->zpos;
dy = target->ypos - agent->ypos;
dx = target->xpos - agent->xpos;
//work out the *relative* angle of the target to the agent
//if it's time for the agent to flee, reverse the angle
//It's a good idea to initialize agents with the timer
//set to a small random value. That way, the swarm will
//gradually disperse over time.
if (agent->timer < (RAT_LIFE_TIME - RAT_FLEE_TIME))
angle = ATAN(dz, dx) - agent->yrot;
else
angle = agent->yrot - ATAN(dz, dx);
//It wasn't done here, but one could influence
//the swarm depending on the way the player is facing.
//One could also extrapolate player movement to set up the
//player's likely future position as the target
//Hit the player if within range
//(using your favored collision method)
//Here: a simple collision box.
if (abs(dz) < AGENT_HIT_RANGE && abs(dy) < AGENT_HIT_RANGE
&& abs(dx) < AGENT_HIT_RANGE)
{target->hp-=AGENT_DAMAGE;}
if (!agent->falling)
// steer because not the agent is not falling
{
//if the target is outside your set range,
//go (roughly) towards it
if (abs(dz) + abs(dx) > SWARM_RANGE)
{
//increase speed to the maximum for this creature
//give each creature a slightly different maximum
//(done here by & the index with 0x1f)
if (agent->speed < 24 + (i & 0x1f))
agent->speed++;
if (abs(angle) < AGENT_LOCK_ANGLE)
{
//vary the steering each cycle - more organic
agent->yrot += (global_counter - i) << 3;
}
else if (angle < 0)
agent->yrot -= AGENT_TURN_SPEED<<1;
else
agent->yrot += AGENT_TURN_SPEED<<1;
}
else
//if the target is roughly within a short range,
//swirl around it
{
if (agent->speed & 0x1)
agent->yrot += AGENT_TURN_SPEED;
else
agent->yrot -= AGENT_TURN_SPEED;
//play around with the numbers in this next line
//to get a variety of different behaviors
agent->speed = 48 - (abs(angle) >> 10);
}
}
//end of steering
h = FloorHeight(agent->x_pos,agent->y_pos,agent->z_pos);
if (h < agent->ypos - AGENT_MAX_STEP)
//If the agent's new position would be much higher
//than its current position, bounce it off the wall
//by resetting its position and changing its angle
{
//if the agent hits a wall while it's fleeing,
//deactivate it. This looks fine with small creatures
if (agent->timer > (AGENT_LIFE_TIME - AGENT_FLEE_TIME))
agent->active = 0;
if (angle > 0)
agent->yrot += 180_DEGREES;
else
agent->yrot -= 180_DEGREES;
agent->xpos = oldx;
agent->ypos = oldy;
agent->zpos = oldz;
agent->fallspeed = 0;
}
//If the agent's new position would take it onto a
//block of climbable height, angle its body upward,
//reset its x and z position and move it upwards
else if (h < agent->ypos - AGENT_IGNORE_STEP)
{
fx->pos.x_rot = AGENT_CLIMB_ANGLE;
fx->pos.x_pos = oldx;
fx->pos.y_pos = oldy - AGENT_CLIMB_SPEED;
fx->pos.z_pos = oldz;
fx->fallspeed = 0;
}
else if (agent->ypos > h)
//the agent is below the floor surface, so move it up to //the floor, reset its fallspeed and set falling to 0. //This happens every cycle the agent isn't in the air //(as we always try to change the y-pos due to gravity)
{
agent->ypos = h;
agent->fallspeed = 0;
agent->falling = 0;
}
if (agent->fallspeed < AGENT_MAX_FALLSPEED &&
agent->timer < AGENT_LIFE_TIME)
//tilt things as they fall
agent->xrot = -(agent->fallspeed << 6);
else
//if they fall too fast or time's run out, kill them
