Particle.cpp

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// ----------------------------------------------------------------------------
// -                        CloudViewer: www.cloudViewer.org                  -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2024 www.cloudViewer.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------
 
#include "Particle.h"
/* This is one of the important methods, where the time is progressed a single
step size (TIME_STEPSIZE) The method is called by Cloth.time_step() Given the
equation "force = mass * acceleration" the next position is found through verlet
integration*/
void Particle::timeStep() {
    if (movable) {
        Vec3 temp = pos;
        pos = pos + (pos - old_pos) * (1.0 - DAMPING) +
              acceleration * time_step2;
        old_pos = temp;
        // acceleration = Vec3(0, 0, 0); // acceleration is reset since it HAS
        // been translated into a change in position (and implicitely into
        // velocity)
    }
}
 
// we precompute the overall displacement of a particle accroding to the
// rigidness const double singleMove1[15] = {0, 0.4, 0.64, 0.784, 0.8704,
// 0.92224, 0.95334, 0.97201, 0.9832, 0.98992, 0.99395, 0.99637, 0.99782,
// 0.99869, 0.99922 };
const double singleMove1[15] = {0,       0.3,     0.51,    0.657,   0.7599,
                                0.83193, 0.88235, 0.91765, 0.94235, 0.95965,
                                0.97175, 0.98023, 0.98616, 0.99031, 0.99322};
// 当有两端移动时
//  const double doubleMove1[15] = {0, 0.4, 0.48, 0.496, 0.4992, 0.49984,
//  0.49997, 0.49999, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5 };
const double doubleMove1[15] = {0,      0.3,   0.42,   0.468,  0.4872,
                                0.4949, 0.498, 0.4992, 0.4997, 0.4999,
                                0.4999, 0.5,   0.5,    0.5,    0.5};
 
void Particle::satisfyConstraintSelf(int constraintTimes) {
    Particle *p1 = this;
    for (int i = 0; i < neighborsList.size(); i++) {
        Particle *p2 = neighborsList[i];
        Vec3 correctionVector(0, p2->pos.y - p1->pos.y, 0);
        if (p1->isMovable() && p2->isMovable()) {
            Vec3 correctionVectorHalf =
                    correctionVector *
                    (constraintTimes > 14
                             ? 0.5
                             : doubleMove1
                                       [constraintTimes]);  // Lets make it half
                                                            // that length, so
                                                            // that we can move
                                                            // BOTH p1 and p2.
            p1->offsetPos(correctionVectorHalf);
            p2->offsetPos(-correctionVectorHalf);
        } else if (p1->isMovable() && !p2->isMovable()) {
            Vec3 correctionVectorHalf =
                    correctionVector *
                    (constraintTimes > 14
                             ? 1
                             : singleMove1
                                       [constraintTimes]);  // Lets make it half
                                                            // that length, so
                                                            // that we can move
                                                            // BOTH p1 and p2.
            p1->offsetPos(correctionVectorHalf);
        } else if (!p1->isMovable() && p2->isMovable()) {
            Vec3 correctionVectorHalf =
                    correctionVector *
                    (constraintTimes > 14
                             ? 1
                             : singleMove1
                                       [constraintTimes]);  // Lets make it half
                                                            // that length, so
                                                            // that we can move
                                                            // BOTH p1 and p2.
            p2->offsetPos(-correctionVectorHalf);
        }
    }
}