Experiment 2 ： Gathering and obstacle avoidance
one , Experimental purpose
Master the artificial intelligence algorithm of aggregation and obstacle avoidance in the game , Understand the difference between wide vision and limited vision
two , Experimental instrument
Microsoft Visual Studio2019
three , Experimental principle and process
// Describe the algorithm principle of aggregation and obstacle avoidance
// Describe the idea of program implementation, including the description of each call API Detailed description
The agent only considers which obstacles are in the detection box .
1. At the beginning , All obstacles in the game world should be iterated into memory , And mark the obstacles in the detection box for further analysis , Then all the marked obstacles are transformed into the local space of the agent .
2. After converting coordinates , those x Objects with negative coordinates will not be considered , So the problem becomes much simpler , Next, it is necessary to detect whether the obstacle overlaps with the detection box . Expand the surrounding radius of the obstacle by half the width of the detection box . Then test the of the obstacle y Is the value less than this value （ That is, the surrounding radius of the obstacle plus half of the width of the detection box ）.
here , There are only those obstacles that intersect the detection box .
3. Next, we find the intersection point closest to the agent .
Calculate again in local space , In the third step, the surrounding radius of the obstacle is expanded .
The expanded circle sum can be obtained by using a simple line circumference intersection test method x Intersection of axes .
four , experimental result
five , Experimental experience ( What deficiencies need to be included and how to improve )
// What do you think are the shortcomings of the current gathering and obstacle avoidance , How to improve
There are still some deficiencies in the design of the program , There are still some minor flaws in obstacle avoidance , Occasionally, obstacle avoidance is not carried out , But it is also a rare time .
Only by constantly improving the code and algorithm for reasonable and correct calculation .
six , Main code
#include "main.h"
#include "time.h"
//---------------------------------------------------------------------------
/*
Book: AI for Game Developers
Authors: David M. Bourg & Glenn Seemann
Example: Flocking, Chapter 4
*/
//---------------------------------------------------------------------------
#define _TIMESTEP 0.0025
#define _TOL 1e-10
#define _FWDTIME 10
#define _THRUSTFACTOR 1.0
#define _CHASESETUP true
#define _SPAWN_AREA_R 100
#define _MAX_NUM_UNITS 20
#define _UNIT_LENGTH 4
#define _OBSTACLE_RADIUS_FACTOR 8
#define _OBSTACLE_RADIUS _OBSTACLE_RADIUS_FACTOR
* _UNIT_LENGTH
#define _COLLISION_VISIBILITY_FACTOR 25
#define _WIDEVIEW_RADIUS_FACTOR 200
#define _NARROWVIEW_RADIUS_FACTOR 50
#define _LIMITEDVIEW_RADIUS_FACTOR 30
#define _SEPARATION_FACTOR 5
#define _BACK_VIEW_ANGLE_FACTOR 1
#define _FRONT_VIEW_ANGLE_FACTOR 1
#define _NUM_OBSTACLES 8
// Global Variables:
int FrameCounter = 0;
RigidBody2D Units[_MAX_NUM_UNITS];
Vector Target;
Vector Obstacles[_NUM_OBSTACLES];
bool Initialize(void)
{
int i;
GetRandomNumber(0, _WINWIDTH, true);
for(i=0; i<_MAX_NUM_UNITS; i++)
{
Units[i].fMass = 10;
Units[i].fInertia = 10;
Units[i].fInertiaInverse = 1/10;
Units[i].vPosition.x =
GetRandomNumber(_WINWIDTH/2-_SPAWN_AREA_R, _WINWIDTH/2+_SPAWN_AREA_R, false);
Units[i].vPosition.y =
GetRandomNumber(_WINHEIGHT/2-_SPAWN_AREA_R, _WINHEIGHT/2+_SPAWN_AREA_R, false);
Units[i].fWidth = _UNIT_LENGTH/2;
Units[i].fLength = _UNIT_LENGTH;
Units[i].fHeight = _UNIT_LENGTH;
Units[i].fOrientation = GetRandomNumber(0, 360, false);
Units[i].CD.y = -0.12*Units[i].fLength; Units[i].CD.x =
0.0f; // coordinates of the body center of drag
Units[i].CT.y = -0.50*Units[i].fLength; Units[i].CT.x =
0.0f; // coordinates of the propeller thrust vector
Units[i].CPT.y = 0.5*Units[i].fLength; Units[i].CPT.x =
-0.5*Units[i].fWidth; // coordinates of the port bow thruster
Units[i].CST.y = 0.5*Units[i].fLength; Units[i].CST.x =
0.5*Units[i].fWidth; // coordinates of the starboard bow thruster
Units[i].ProjectedArea = (Units[i].fLength + Units[i].fWidth) *
Units[i].fHeight;
Units[i].Leader = false;
if(i>_MAX_NUM_UNITS/2)
{
Units[i].Interceptor = true;
Units[i].ThrustForce = _THRUSTFORCE*1.5f;
} else {
Units[i].Interceptor = false;
Units[i].ThrustForce = _THRUSTFORCE;
}
}
for(i=0; i<_NUM_OBSTACLES; i++)
{
Obstacles[i].x = GetRandomNumber(_OBSTACLE_RADIUS*4,
_WINWIDTH-_OBSTACLE_RADIUS*4, false);
Obstacles[i].y =
/*_WINHEIGHT/2;*/GetRandomNumber(_OBSTACLE_RADIUS*4,
_WINHEIGHT-_OBSTACLE_RADIUS*4, false);
}
return true;
}
void DoUnitAI(int i)
{
int j;
int N;
Vector Pave;
Vector Vave;
Vector Fs;
Vector Pfs;
Vector d, u, v, w;
double m;
int Nf;
bool InView;
bool DoFlock = WideView || LimitedView || NarrowView;
int RadiusFactor;
// begin Flock AI
Fs.x = Fs.y = Fs.z = 0;
Pave.x = Pave.y = Pave.z = 0;
Vave.x = Vave.y = Vave.z = 0;
N = 0;
Pfs.x = 0;
Pfs.y = Units[i].fLength / 2.0f;
Nf = 0;
for(j=1; j<_MAX_NUM_UNITS; j++)
{
if(i!=j)
{
InView = false;
d = Units[j].vPosition - Units[i].vPosition;
w = VRotate2D(-Units[i].fOrientation, d);
if(((w.y > 0) && (fabs(w.x) <
fabs(w.y)*_FRONT_VIEW_ANGLE_FACTOR)))
if(d.Magnitude() <= (Units[i].fLength *
_NARROWVIEW_RADIUS_FACTOR))
Nf++;
if(WideView)
{
InView = ((w.y > 0) || ((w.y < 0) &&
(fabs(w.x) > fabs(w.y)*_BACK_VIEW_ANGLE_FACTOR)));
RadiusFactor = _WIDEVIEW_RADIUS_FACTOR;
}
if(LimitedView)
{
InView = (w.y > 0);
RadiusFactor = _LIMITEDVIEW_RADIUS_FACTOR;
}
if(NarrowView)
{
InView = (((w.y > 0) && (fabs(w.x) <
fabs(w.y)*_FRONT_VIEW_ANGLE_FACTOR)));
RadiusFactor = _NARROWVIEW_RADIUS_FACTOR;
}
if(InView && (Units[i].Interceptor ==
Units[j].Interceptor))
{
if(d.Magnitude() <= (Units[i].fLength *
RadiusFactor))
{
Pave += Units[j].vPosition;
Vave += Units[j].vVelocity;
N++;
}
}
// Separation Rule:
if(InView)//(w.y > 0) || ((w.y < 0) && (fabs(w.x)
> fabs(w.y)*_BACK_VIEW_ANGLE_FACTOR)))
{
if(d.Magnitude() <= (Units[i].fLength *
_SEPARATION_FACTOR))
{
if(w.x < 0) m = 1;
if(w.x > 0) m =
-1;
Fs.x += m*_STEERINGFORCE *
(Units[i].fLength * _SEPARATION_FACTOR) / d.Magnitude();
}
}
}
}
// Cohesion Rule:
if(DoFlock && (N > 0))
{
Pave = Pave / N;
v = Units[i].vVelocity;
v.Normalize();
u = Pave - Units[i].vPosition;
u.Normalize();
w = VRotate2D(-Units[i].fOrientation, u);
if(w.x < 0) m = -1;
if(w.x > 0) m = 1;
if(fabs(v*u) < 1.0f)
Fs.x += m * _STEERINGFORCE * acos(v * u) / pi;
}
// Alignment Rule:
if(DoFlock && (N > 0))
{
Vave = Vave / N;
u = Vave;
u.Normalize();
v = Units[i].vVelocity;
v.Normalize();
w = VRotate2D(-Units[i].fOrientation, u);
if(w.x < 0) m = -1;
if(w.x > 0) m = 1;
if(fabs(v*u) < 1)
Fs.x += m * _STEERINGFORCE * acos(v * u) / pi;
}
// Chase the target if the unit is a leader
if(Chase)
{
if(Nf == 0)
Units[i].Leader = true;
else
Units[i].Leader = false;
if((Units[i].Leader || !DoFlock))
{
if(!Units[i].Interceptor)
{
//
Chase
u = Units[0].vPosition;
d = u - Units[i].vPosition;
w = VRotate2D(-Units[i].fOrientation, d);
if(w.x < 0) m = -1;
if(w.x > 0) m = 1;
Fs.x += m*_STEERINGFORCE;
} else {
// Intercept
Vector s1, s2, s12;
double tClose;
Vector Vr12;
Vr12 =
Units[0].vVelocity-Units[i].vVelocity; // closing velocity
s12 = Units[0].vPosition -
Units[i].vPosition; // range to close
tClose = s12.Magnitude() /
Vr12.Magnitude(); // time to close
s1 = Units[0].vPosition +
(Units[0].vVelocity * tClose);
Target = s1;
s2 = s1 - Units[i].vPosition;
w = VRotate2D(-Units[i].fOrientation, s2);
if(w.x < 0) m = -1;
if(w.x > 0) m = 1;
Fs.x += m*_STEERINGFORCE;
}
}
}
// Collision avoidance (with static obstacles)
Vector a, p, b;
for(j=0; j<_NUM_OBSTACLES; j++)
{
u = Units[i].vVelocity;
u.Normalize();
v = u * _COLLISION_VISIBILITY_FACTOR * Units[i].fLength;
a = Obstacles[j] - Units[i].vPosition;
p = (a * u) * u;
b = p - a;
if((b.Magnitude() < _OBSTACLE_RADIUS) && (p.Magnitude() <
v.Magnitude()))
{
// impending collision...steer away
w = VRotate2D(-Units[i].fOrientation, a);
w.Normalize();
if(w.x < 0) m = 1;
if(w.x > 0) m = -1;
Fs.x += m * _STEERINGFORCE *
(_COLLISION_VISIBILITY_FACTOR * Units[i].fLength)/a.Magnitude();
}
}
// apply accumulated steering force
Units[i].Fa = Fs;
Units[i].Pa = Pfs;
// end Flock AI
}
void UpdateSimulation(void)
{
double dt = _TIMESTEP;
int i;
// initialize the back buffer
if(FrameCounter >= _RENDER_FRAME_COUNT)
{
ClearBackBuffer();
DrawObstacles();
}
// Update player controlled unit:
Units[0].SetThrusters(false, false, 1);
Units[0].SetThrusters(false, false, 1);
if (IsKeyDown(VK_RIGHT))
Units[0].SetThrusters(true, false, 0.5);
if (IsKeyDown(VK_LEFT))
Units[0].SetThrusters(false, true, 0.5);
Units[0].UpdateBodyEuler(dt);
if(FrameCounter >= _RENDER_FRAME_COUNT)
DrawCraft(Units[0], RGB(0, 255, 0));
if(Units[0].vPosition.x > _WINWIDTH) Units[0].vPosition.x = 0;
if(Units[0].vPosition.x < 0) Units[0].vPosition.x = _WINWIDTH;
if(Units[0].vPosition.y > _WINHEIGHT) Units[0].vPosition.y = 0;
if(Units[0].vPosition.y < 0) Units[0].vPosition.y = _WINHEIGHT;
// update computer controlled units:
for(i=1; i<_MAX_NUM_UNITS; i++)
{
DoUnitAI(i);
Units[i].UpdateBodyEuler(dt);
if(FrameCounter >= _RENDER_FRAME_COUNT)
{
if(Units[i].Leader)
DrawCraft(Units[i], RGB(255,0,0));
else {
if(Units[i].Interceptor)
DrawCraft(Units[i], RGB(255,0,255));
else
DrawCraft(Units[i], RGB(0,0,255));
}
}
if(Units[i].vPosition.x > _WINWIDTH) Units[i].vPosition.x = 0;
if(Units[i].vPosition.x < 0) Units[i].vPosition.x = _WINWIDTH;
if(Units[i].vPosition.y > _WINHEIGHT) Units[i].vPosition.y = 0;
if(Units[i].vPosition.y < 0) Units[i].vPosition.y =
_WINHEIGHT;
} // end i-loop
if(FrameCounter >= _RENDER_FRAME_COUNT) {
CopyBackBufferToWindow();
FrameCounter = 0;
} else
FrameCounter++;
}
void DrawCraft(RigidBody2D craft, COLORREF clr)
{
Vector vList[5];
double wd, lg;
int i;
Vector v1;
wd = craft.fWidth;
lg = craft.fLength;
vList[0].y = lg/2; vList[0].x = wd/2;
vList[1].y = -lg/2; vList[1].x = wd/2;
vList[2].y = -lg/2; vList[2].x = -wd/2;
vList[3].y = lg/2; vList[3].x = -wd/2;
vList[4].y = lg/2*1.5; vList[4].x = 0;
for(i=0; i<5; i++)
{
v1 = VRotate2D(craft.fOrientation, vList[i]);
vList[i] = v1 + craft.vPosition;
}
DrawLine(vList[0].x, vList[0].y, vList[1].x, vList[1].y, 2, clr);
DrawLine(vList[1].x, vList[1].y, vList[2].x, vList[2].y, 2, clr);
DrawLine(vList[2].x, vList[2].y, vList[3].x, vList[3].y, 2, clr);
DrawLine(vList[3].x, vList[3].y, vList[4].x, vList[4].y, 2, clr);
DrawLine(vList[4].x, vList[4].y, vList[0].x, vList[0].y, 2, clr);
if(ShowVectors)
{
Vector v, u;
double f = 0.025;
// Show velocity vectors in green
DrawLine(craft.vPosition.x, craft.vPosition.y,
craft.vPosition.x+craft.vVelocity.x, craft.vPosition.y+craft.vVelocity.y, 3,
RGB(0,255,0));
// Show force vectors in black
// thrust vector
v.x = 0;
v.y = craft.ThrustForce*f;
v = VRotate2D(craft.fOrientation, v);
u.x = craft.CT.x;
u.y = craft.CT.y;
u = VRotate2D(craft.fOrientation, u);
DrawLine(craft.vPosition.x+u.x, craft.vPosition.y+u.y,
craft.vPosition.x + u.x + v.x, craft.vPosition.y + u.y + v.y, 1, RGB(0,0,0));
// port steering force
v.x = craft.PThrust.x*f;
v.y = craft.PThrust.y*f;
v = VRotate2D(craft.fOrientation, v);
u.x = craft.CPT.x;
u.y = craft.CPT.y;
u = VRotate2D(craft.fOrientation, u);
DrawLine(craft.vPosition.x+u.x, craft.vPosition.y+u.y,
craft.vPosition.x + u.x + v.x, craft.vPosition.y + u.y + v.y, 1, RGB(0,0,0));
// stbd steering force
v.x = craft.SThrust.x*f;
v.y = craft.SThrust.y*f;
v = VRotate2D(craft.fOrientation, v);
u.x = craft.CST.x;
u.y = craft.CST.y;
u = VRotate2D(craft.fOrientation, u);
DrawLine(craft.vPosition.x+u.x, craft.vPosition.y+u.y,
craft.vPosition.x + u.x + v.x, craft.vPosition.y + u.y + v.y, 1, RGB(0,0,0));
// applied force
v.x = craft.Fa.x*f;
v.y = craft.Fa.y*f;
v = VRotate2D(craft.fOrientation, v);
u.x = craft.Pa.x;
u.y = craft.Pa.y;
u = VRotate2D(craft.fOrientation, u);
DrawLine(craft.vPosition.x+u.x, craft.vPosition.y+u.y,
craft.vPosition.x + u.x + v.x, craft.vPosition.y + u.y + v.y, 1, RGB(0,0,0));
}
}
void DrawObstacles(void)
{
int i;
RECT r;
int radius = _OBSTACLE_RADIUS/2;
for(i=0; i<_NUM_OBSTACLES; i++)
{
SetRect(&r, Obstacles[i].x - radius, Obstacles[i].y - radius,
Obstacles[i].x + radius, Obstacles[i].y + radius);
DrawEllipse(&r, 2, RGB(255,0,0));
}
}
/*
void DoAttractCraft2(void)
{
// Apply Leonard-Jones potential force to Craft2
// todo: make sure rigidbody calcloads function handles it
Vector r = Craft2.vPosition - Craft1.vPosition;
Vector u = r;
u.Normalize();
double k1 = 0.5e2; // repel
double k2 = 1.0e2; // attract
Craft2.Fa = VRotate2D( -Craft2.fOrientation,
((k1*pow(Craft2.fLength*5/r.Magnitude(), 4) -
k2*pow(Craft2.fLength*3/r.Magnitude(), 2)) ) * u);
Craft2.Pa.x = 0;
Craft2.Pa.y = Craft2.fLength / 2;
Target = Craft1.vPosition;
}
*/
int GetRandomNumber(int min, int max, bool seed)
{
int number;
if(seed)
srand( (unsigned)time( NULL ) );
number = (((abs(rand())%(max-min+1))+min));
if(number>max)
number = max;
if(number<min)
number = min;
return number;
}
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