97 lines
3.1 KiB
C++
97 lines
3.1 KiB
C++
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/*
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* Copyright (C) 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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#include "Boid.h"
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Boid::Boid(float x, float y) :
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mPosition(x, y) {
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}
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void Boid::flock(const Boid* boids[], int numBoids, int index, float limitX, float limitY) {
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// Reset the acceleration.
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mAcceleration.mX = 0;
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mAcceleration.mY = 0;
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Vector2D separation;
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int separationCount = 0;
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Vector2D alignment;
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int alignmentCount = 0;
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Vector2D cohesion;
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int cohesionCount = 0;
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for (int i = 0; i < numBoids; i++) {
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if (i != index) {
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const Boid* b = boids[i];
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float dist = mPosition.distance(b->mPosition);
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if (dist != 0) {
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// Separation.
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if (dist < DESIRED_BOID_DIST) {
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Vector2D tmp = mPosition.copy();
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tmp.sub(b->mPosition);
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tmp.normalize();
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tmp.scale(1.0f / dist);
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separation.add(tmp);
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separationCount++;
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}
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if (dist < NEIGHBOUR_RADIUS) {
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// Alignment.
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alignment.add(b->mVelocity);
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alignmentCount++;
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// Cohesion.
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cohesion.add(b->mPosition);
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cohesionCount++;
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}
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}
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}
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}
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if (separationCount > 0) {
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separation.scale(1.0f / separationCount);
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separation.scale(SEPARATION_WEIGHT);
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mAcceleration.add(separation);
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}
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if (alignmentCount > 0) {
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alignment.scale(1.0f / alignmentCount);
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alignment.limit(MAX_FORCE);
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alignment.scale(ALIGNMENT_WEIGHT);
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mAcceleration.add(alignment);
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}
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if (cohesionCount > 0) {
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cohesion.scale(1.0f / cohesionCount);
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cohesion.scale(COHESION_WEIGHT);
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Vector2D desired = cohesion.copy();
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desired.sub(mPosition);
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float d = desired.magnitude();
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if (d > 0) {
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desired.normalize();
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desired.scale(MAX_SPEED * ((d < 100.0f) ? d / 100.0f : 1));
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desired.sub(mVelocity);
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desired.limit(MAX_FORCE);
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mAcceleration.add(desired);
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}
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}
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mVelocity.add(mAcceleration);
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mVelocity.limit(MAX_SPEED);
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mPosition.add(mVelocity);
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// Wrap around.
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if (mPosition.mX < -limitX) {
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mPosition.mX = limitX;
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} else if (mPosition.mX > limitX) {
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mPosition.mX = -limitX;
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}
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if (mPosition.mY < -limitY) {
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mPosition.mY = limitY;
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} else if (mPosition.mY > limitY) {
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mPosition.mY = -limitY;
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}
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}
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