FLOCK.CPP

/* 
**----------------------------------------------------------------------------- 
**File:flock.cpp  
**Purpose:-- where the boids are 
**Notes: 
** 
**  Copyright (c) 1995 - 1997 by Microsoft, all rights reserved. 
**----------------------------------------------------------------------------- 
*/ 
 
/* 
**----------------------------------------------------------------------------- 
** Include Files 
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*/ 
 
#include "Common.h" 
#include "Debug.h" 
#include "d3dutils.h" 
#include "boids.h" 
 
 
 
/* 
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** Constants 
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*/ 
 
const float InfluenceRadius = 20.0f; 
const float InfluenceRadiusSquared = InfluenceRadius * InfluenceRadius; 
const float CollisionFraction = 0.8f; 
const float InvCollisionFraction = 1.0f/(1.0f-CollisionFraction); 
 
const float NormalSpeed = 0.1f; 
const floatAngleTweak = 0.02f; 
const float PitchToSpeedRatio = 0.002f; 
 
 
 
/* 
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** Functions 
**----------------------------------------------------------------------------- 
*/ 
 
/* 
**----------------------------------------------------------------------------- 
** Name:UpdateFlock 
** Purpose:Update posiiton of each boid in flock 
**----------------------------------------------------------------------------- 
*/ 
 
void 
UpdateFlock (Flock flock) 
{ 
inti, j; 
floatdist; 
 
// first update the dist array 0.0..1.0 with 0.0 being furthest away 
for (i=0; i<flock.num_boids; i++) { 
for (j=i+1; j<flock.num_boids; j++) { 
dist = SquareMagnitude(flock.boids[i].loc - flock.boids[j].loc); 
dist = InfluenceRadiusSquared - dist; 
if (dist < 0.0f) { 
dist = 0.0f; 
} else { 
dist /= InfluenceRadiusSquared; 
} 
flock.dist[i][j] = flock.dist[j][i] = dist; 
} 
flock.dist[i][i] = 0.0f; 
flock.boids[i].delta_dir = D3DVECTOR(0.0f); 
flock.boids[i].delta_pos = D3DVECTOR(0.0f); 
flock.boids[i].delta_cnt = 0; 
} 
 
for (i=0; i<flock.num_boids; i++) { 
for (j=i+1; j<flock.num_boids; j++) { 
// if i is near j have them influence each other 
if (flock.dist[i][j] > 0.0) { 
D3DVECTORdiff = Normalize(flock.boids[i].loc - flock.boids[j].loc); 
D3DVECTORdelta; 
floatcol = 0.0f;// collision weighting 
 
// only do collision testing against the nearest ones 
if (flock.dist[i][j] - CollisionFraction > 0.0f) { 
col = (flock.dist[i][j] - CollisionFraction) * InvCollisionFraction; 
} 
 
// add in a little flock centering 
if (flock.dist[i][j] - (1.0-CollisionFraction) > 0.0f) { 
col -= flock.dist[i][j] * (1.0f-col); 
} 
 
delta = col * diff; 
 
// add in the collision avoidance 
flock.boids[i].delta_pos += delta; 
flock.boids[j].delta_pos -= delta; 
 
// add in the velocity influences 
flock.boids[i].delta_dir += flock.boids[j].dir * flock.dist[i][j]; 
flock.boids[j].delta_dir += flock.boids[i].dir * flock.dist[i][j]; 
flock.boids[i].delta_cnt++; 
flock.boids[j].delta_cnt++; 
} 
} 
} 
 
// update the boids 
for (i=0; i<flock.num_boids; i++) { 
if (flock.boids[i].delta_cnt) { 
flock.boids[i].delta_dir /= (float)flock.boids[i].delta_cnt; 
flock.boids[i].delta_dir -= flock.boids[i].dir; 
flock.boids[i].delta_dir *= 1.5f; 
} 
D3DVECTORdelta = flock.boids[i].delta_dir + flock.boids[i].delta_pos; // + 0.1f * D3DVECTOR(rnd()-rnd(), rnd()-rnd(), rnd()-rnd()); 
D3DVECTORoffset; 
 
//delta = Normalize(delta); 
 
// add in the influence of the global goal 
D3DVECTORgoal = 0.5f * Normalize(flock.goal-flock.boids[i].loc); 
delta += goal; 
 
// add in any obstacles 
for (j=0; j<flock.num_obs; j++) { 
D3DVECTORob = flock.boids[i].loc - flock.obs[j].loc; 
floatradius = flock.obs[j].radius; 
floatdist = Magnitude(ob); 
 
if (dist > 2*radius) 
continue; 
 
ob /= dist;// normalize 
dist = 1.0f - dist/(2.0f*radius); 
delta += dist * ob * 5.0f; 
} 
 
// first deal with pitch changes 
if (delta.y > 0.01) {// we're too low 
flock.boids[i].pitch += AngleTweak; 
if (flock.boids[i].pitch > 0.8f) 
flock.boids[i].pitch = 0.8f; 
} else if (delta.y < -0.01) {// we're too high 
flock.boids[i].pitch -= AngleTweak; 
if (flock.boids[i].pitch < -0.8f) 
flock.boids[i].pitch = -0.8f; 
} else { 
// add damping 
flock.boids[i].pitch *= 0.98f; 
} 
 
// speed up or slow down depending on angle of attack 
flock.boids[i].speed -= flock.boids[i].pitch * PitchToSpeedRatio; 
// damp back to normal 
flock.boids[i].speed = (flock.boids[i].speed-NormalSpeed)*0.99f + NormalSpeed; 
 
if (flock.boids[i].speed < NormalSpeed/2) { 
flock.boids[i].speed = NormalSpeed/2; 
} 
if (flock.boids[i].speed > NormalSpeed*5) { 
flock.boids[i].speed = NormalSpeed*5; 
} 
 
// now figure out yaw changes 
offset = delta; 
offset.y = 0.0f; 
delta = flock.boids[i].dir; 
offset = Normalize(offset); 
floatdot = DotProduct(offset, delta); 
// speed up slightly if not turning much 
if (dot > 0.7f) { 
dot -= 0.7f; 
flock.boids[i].speed += dot * 0.005f; 
} 
offset = CrossProduct(offset, delta); 
dot = (1.0f-dot)/2.0f * 0.07f; 
if (offset.y > 0.05f) { 
flock.boids[i].dyaw = (flock.boids[i].dyaw*19.0f + dot) * 0.05f; 
} else if (offset.y < -0.05f) { 
flock.boids[i].dyaw = (flock.boids[i].dyaw*19.0f - dot) * 0.05f; 
} else { 
flock.boids[i].dyaw *= 0.98f;// damp it 
} 
flock.boids[i].yaw += flock.boids[i].dyaw; 
flock.boids[i].roll = -flock.boids[i].dyaw * 20.0f; 
 
 
} 
 
}// end of UpdateFlock() 
 
 
/* 
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** End of File 
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*/