]> git.localhorst.tv Git - blobs.git/blobdiff - src/creature/creature.cpp
change mode of steering mixing
[blobs.git] / src / creature / creature.cpp
index d0000107b683e5b454d1864ba65c9c4c6dfe3873..1a88dba1ab7d76831972bdaa3b0fab4d3e7b0973 100644 (file)
@@ -11,6 +11,7 @@
 #include "IdleGoal.hpp"
 #include "../app/Assets.hpp"
 #include "../math/const.hpp"
+#include "../ui/string.hpp"
 #include "../world/Body.hpp"
 #include "../world/Planet.hpp"
 #include "../world/Simulation.hpp"
@@ -29,7 +30,8 @@ namespace blobs {
 namespace creature {
 
 Composition::Composition()
-: components() {
+: components()
+, total_mass(0.0) {
 }
 
 Composition::~Composition() {
@@ -43,17 +45,21 @@ bool CompositionCompare(const Composition::Component &a, const Composition::Comp
 
 void Composition::Add(int res, double amount) {
        bool found = false;
-       for (auto &c : components) {
-               if (c.resource == res) {
-                       c.value += amount;
+       for (auto c = components.begin(); c != components.end(); ++c) {
+               if (c->resource == res) {
+                       c->value += amount;
+                       if (c->value <= 0.0) {
+                               components.erase(c);
+                       }
                        found = true;
                        break;
                }
        }
-       if (!found) {
+       if (!found && amount > 0.0) {
                components.emplace_back(res, amount);
        }
        std::sort(components.begin(), components.end(), CompositionCompare);
+       total_mass += amount;
 }
 
 bool Composition::Has(int res) const noexcept {
@@ -86,8 +92,10 @@ Creature::Creature(world::Simulation &sim)
 , mass(1.0)
 , size(1.0)
 , birth(sim.Time())
+, death(-1.0)
 , on_death()
 , removable(false)
+, parents()
 , stats()
 , memory(*this)
 , bg_task()
@@ -95,6 +103,7 @@ Creature::Creature(world::Simulation &sim)
 , situation()
 , steering(*this)
 , vao() {
+       sim.SetAlive(this);
        // all creatures avoid each other for now
        steering.Separate(0.1, 1.5);
 }
@@ -104,19 +113,17 @@ Creature::~Creature() {
 
 void Creature::AddMass(int res, double amount) {
        composition.Add(res, amount);
-       double mass = 0.0;
        double nonsolid = 0.0;
        double volume = 0.0;
        for (const auto &c : composition) {
-               mass += c.value;
                volume += c.value / sim.Assets().data.resources[c.resource].density;
                if (sim.Assets().data.resources[c.resource].state != world::Resource::SOLID) {
                        nonsolid += c.value;
                }
        }
-       Mass(mass);
+       Mass(composition.TotalMass());
        Size(std::cbrt(volume));
-       highlight_color.a = nonsolid / mass;
+       highlight_color.a = nonsolid / composition.TotalMass();
 }
 
 void Creature::HighlightColor(const glm::dvec3 &c) noexcept {
@@ -125,15 +132,87 @@ void Creature::HighlightColor(const glm::dvec3 &c) noexcept {
 
 void Creature::Ingest(int res, double amount) noexcept {
        // TODO: check foreign materials
-       // 10% stays in body
-       AddMass(res, amount * 0.1);
+       if (sim.Resources()[res].state == world::Resource::SOLID) {
+               // 15% of solids stays in body
+               AddMass(res, amount * 0.15);
+       } else {
+               // 10% of fluids stays in body
+               AddMass(res, amount * 0.05);
+       }
+       math::GaloisLFSR &random = sim.Assets().random;
+       if (random.UNorm() < AdaptChance()) {
+               // change color to be slightly more like resource
+               glm::dvec3 color(rgb2hsl(sim.Resources()[res].base_color));
+               // solids affect base color, others highlight
+               double p = sim.Resources()[res].state == world::Resource::SOLID ? 0 : 1;
+               double q = random.UInt(3); // hue, sat, or val
+               double r = random.UInt(2); // mean or deviation
+               math::Distribution *d = nullptr;
+               double ref = 0.0;
+               if (p == 0) {
+                       if (q == 0) {
+                               d = &genome.base_hue;
+                               ref = color.x;
+                       } else if (q == 1) {
+                               d = &genome.base_saturation;
+                               ref = color.y;
+                       } else {
+                               d = &genome.base_lightness;
+                               ref = color.z;
+                       }
+               } else {
+                       if (q == 0) {
+                               d = &genome.highlight_hue;
+                               ref = color.x;
+                       } else if (q == 1) {
+                               d = &genome.highlight_saturation;
+                               ref = color.y;
+                       } else {
+                               d = &genome.highlight_lightness;
+                               ref = color.z;
+                       }
+               }
+               if (r == 0) {
+                       double diff = ref - d->Mean();
+                       if (q == 0) {
+                               if (diff < -0.5) {
+                                       diff += 1.0;
+                               } else if (diff > 0.5) {
+                                       diff -= 1.0;
+                               }
+                               // move ±15% of distance
+                               d->Mean(std::fmod(d->Mean() + diff * random.SNorm() * 0.15, 1.0));
+                       } else {
+                               d->Mean(glm::clamp(d->Mean() + diff * random.SNorm() * 0.15, 0.0, 1.0));
+                       }
+               } else {
+                       // scale by ±15%, enforce bounds
+                       d->StandardDeviation(glm::clamp(d->StandardDeviation() * (1.0 + random.SNorm() * 0.15), 0.0001, 0.5));
+               }
+       }
+}
+
+void Creature::DoWork(double amount) noexcept {
+       stats.Exhaustion().Add(amount / Stamina());
+       // burn resources proportional to composition
+       // factor = 1/total * 1/efficiency * amount * -1
+       double factor = -amount / (composition.TotalMass() * EnergyEfficiency());
+       // make a copy to total remains constant and
+       // no entries disappear during iteration
+       Composition comp(composition);
+       for (auto &cmp : comp) {
+               double value = cmp.value * factor * sim.Resources()[cmp.resource].inverse_energy;
+               AddMass(cmp.resource, value);
+       }
 }
 
 void Creature::Hurt(double amount) noexcept {
        stats.Damage().Add(amount);
        if (stats.Damage().Full()) {
-               std::cout << "[" << int(sim.Time()) << "s] " << name << " ";
-               if (stats.Breath().Full()) {
+               std::cout << "[" << ui::TimeString(sim.Time()) << "] " << name << " ";
+               if (stats.Exhaustion().Full()) {
+                       std::cout << "died of exhaustion";
+               } else if (stats.Breath().Full()) {
                        std::cout << "suffocated";
                } else if (stats.Thirst().Full()) {
                        std::cout << "died of thirst";
@@ -142,20 +221,45 @@ void Creature::Hurt(double amount) noexcept {
                } else {
                        std::cout << "succumed to wounds";
                }
-               std::cout << std::endl;
+               std::cout << " at an age of " << ui::TimeString(Age())
+                       << " (" << ui::PercentageString(Age() / properties.Lifetime())
+                       << "% of life expectancy of " << ui::TimeString(properties.Lifetime())
+                       << ")" << std::endl;
                Die();
        }
 }
 
 void Creature::Die() noexcept {
-       goals.clear();
-       steering.Halt();
+       if (Dead()) return;
+
+       sim.SetDead(this);
+       death = sim.Time();
+       steering.Off();
        if (on_death) {
                on_death(*this);
        }
        Remove();
 }
 
+bool Creature::Dead() const noexcept {
+       return death > birth;
+}
+
+void Creature::Remove() noexcept {
+       removable = true;
+}
+
+void Creature::Removed() noexcept {
+       bg_task.reset();
+       goals.clear();
+       memory.Erase();
+       KillVAO();
+}
+
+void Creature::AddParent(Creature &p) {
+       parents.push_back(&p);
+}
+
 double Creature::Age() const noexcept {
        return sim.Time() - birth;
 }
@@ -164,7 +268,12 @@ double Creature::AgeFactor(double peak) const noexcept {
        // shifted inverse hermite, y = 1 - (3t² - 2t³) with t = normalized age - peak
        // goes negative below -0.5 and starts to rise again above 1.0
        double t = glm::clamp((Age() / properties.Lifetime()) - peak, -0.5, 1.0);
-       return 1.0 - (3.0 * t * t) + (2.0 * t * t * t);
+       // guarantee at least 1%
+       return std::max(0.01, 1.0 - (3.0 * t * t) + (2.0 * t * t * t));
+}
+
+double Creature::EnergyEfficiency() const noexcept {
+       return 0.25 * AgeFactor(0.05);
 }
 
 double Creature::ExhaustionFactor() const noexcept {
@@ -204,6 +313,10 @@ double Creature::Mutability() const noexcept {
        return properties.Mutability();
 }
 
+double Creature::Adaptability() const noexcept {
+       return properties.Adaptability();
+}
+
 double Creature::OffspringMass() const noexcept {
        return properties.OffspringMass();
 }
@@ -216,6 +329,10 @@ double Creature::MutateChance() const noexcept {
        return GetProperties().Mutability() * (1.0 / 3600.0);
 }
 
+double Creature::AdaptChance() const noexcept {
+       return GetProperties().Adaptability() * (1.0 / 120.0);
+}
+
 void Creature::AddGoal(std::unique_ptr<Goal> &&g) {
        g->Enable();
        goals.emplace_back(std::move(g));
@@ -249,10 +366,11 @@ void Creature::TickState(double dt) {
        );
        state.pos += f.vel * dt;
        state.vel += f.acc * dt;
+       situation.EnforceConstraints(state);
        if (length2(state.vel) > 0.000001) {
                glm::dvec3 nvel(normalize(state.vel));
                double ang = angle(nvel, state.dir);
-               double turn_rate = PI * 0.5 * dt;
+               double turn_rate = PI * 0.75 * dt;
                if (ang < turn_rate) {
                        state.dir = normalize(state.vel);
                } else if (std::abs(ang - PI) < 0.001) {
@@ -262,16 +380,34 @@ void Creature::TickState(double dt) {
                }
        }
        situation.SetState(state);
-       stats.Exhaustion().Add(length(f.acc) * Mass() / Stamina() * dt);
+       // work is force times distance
+       DoWork(length(f.acc) * Mass() * length(f.vel) * dt);
 }
 
 Situation::Derivative Creature::Step(const Situation::Derivative &ds, double dt) const noexcept {
        Situation::State s = situation.GetState();
        s.pos += ds.vel * dt;
        s.vel += ds.acc * dt;
+       glm::dvec3 force(steering.Force(s));
+       // gravity = antinormal * mass * Gm / r²
+       double elevation = s.pos[(situation.Surface() + 2) % 3];
+       glm::dvec3 normal(world::Planet::SurfaceNormal(situation.Surface()));
+       force += glm::dvec3(
+               -normal
+               * Mass() * situation.GetPlanet().GravitationalParameter()
+               / (elevation * elevation));
+       // if net force is applied and in contact with surface
+       if (!allzero(force) && std::abs(std::abs(elevation) - situation.GetPlanet().Radius()) < 0.001) {
+               // apply friction = -|normal force| * tangential force * coefficient
+               glm::dvec3 fn(normal * dot(force, normal));
+               glm::dvec3 ft(force - fn);
+               double u = 0.4;
+               glm::dvec3 friction(-length(fn) * ft * u);
+               force += friction;
+       }
        return {
                s.vel,
-               steering.Force(s) / Mass()
+               force / Mass()
        };
 }
 
@@ -293,6 +429,10 @@ void Creature::TickStats(double dt) {
                constexpr double dps = 1.0 / 128.0;
                Hurt(dps * dt);
        }
+       if (!situation.Moving()) {
+               // double exhaustion recovery when standing still
+               stats.Exhaustion().Add(stats.Exhaustion().gain * dt);
+       }
 }
 
 void Creature::TickBrain(double dt) {
@@ -320,28 +460,38 @@ void Creature::TickBrain(double dt) {
        }
 }
 
-glm::dmat4 Creature::LocalTransform() noexcept {
+math::AABB Creature::CollisionBox() const noexcept {
+       return { glm::dvec3(size * -0.5), glm::dvec3(size * 0.5) };
+}
+
+glm::dmat4 Creature::CollisionTransform() const noexcept {
        const double half_size = size * 0.5;
        const glm::dvec3 &pos = situation.Position();
        const glm::dmat3 srf(world::Planet::SurfaceOrientation(situation.Surface()));
        return glm::translate(glm::dvec3(pos.x, pos.y, pos.z + half_size))
                * glm::rotate(glm::orientedAngle(-srf[2], situation.Heading(), srf[1]), srf[1])
-               * glm::dmat4(srf)
+               * glm::dmat4(srf);
+}
+
+glm::dmat4 Creature::LocalTransform() noexcept {
+       const double half_size = size * 0.5;
+       return CollisionTransform()
                * glm::scale(glm::dvec3(half_size, half_size, half_size));
 }
 
 void Creature::BuildVAO() {
-       vao.Bind();
-       vao.BindAttributes();
-       vao.EnableAttribute(0);
-       vao.EnableAttribute(1);
-       vao.EnableAttribute(2);
-       vao.AttributePointer<glm::vec3>(0, false, offsetof(Attributes, position));
-       vao.AttributePointer<glm::vec3>(1, false, offsetof(Attributes, normal));
-       vao.AttributePointer<glm::vec3>(2, false, offsetof(Attributes, texture));
-       vao.ReserveAttributes(6 * 4, GL_STATIC_DRAW);
+       vao.reset(new graphics::SimpleVAO<Attributes, unsigned short>);
+       vao->Bind();
+       vao->BindAttributes();
+       vao->EnableAttribute(0);
+       vao->EnableAttribute(1);
+       vao->EnableAttribute(2);
+       vao->AttributePointer<glm::vec3>(0, false, offsetof(Attributes, position));
+       vao->AttributePointer<glm::vec3>(1, false, offsetof(Attributes, normal));
+       vao->AttributePointer<glm::vec3>(2, false, offsetof(Attributes, texture));
+       vao->ReserveAttributes(6 * 4, GL_STATIC_DRAW);
        {
-               auto attrib = vao.MapAttributes(GL_WRITE_ONLY);
+               auto attrib = vao->MapAttributes(GL_WRITE_ONLY);
                const float offset = 1.0f;
                for (int surface = 0; surface < 6; ++surface) {
                        const float tex_u_begin = surface < 3 ? 1.0f : 0.0f;
@@ -388,10 +538,10 @@ void Creature::BuildVAO() {
                        attrib[4 * surface + 3].texture.z = surface;
                }
        }
-       vao.BindElements();
-       vao.ReserveElements(6 * 6, GL_STATIC_DRAW);
+       vao->BindElements();
+       vao->ReserveElements(6 * 6, GL_STATIC_DRAW);
        {
-               auto element = vao.MapElements(GL_WRITE_ONLY);
+               auto element = vao->MapElements(GL_WRITE_ONLY);
                for (int surface = 0; surface < 3; ++surface) {
                        element[6 * surface + 0] = 4 * surface + 0;
                        element[6 * surface + 1] = 4 * surface + 2;
@@ -409,12 +559,17 @@ void Creature::BuildVAO() {
                        element[6 * surface + 5] = 4 * surface + 3;
                }
        }
-       vao.Unbind();
+       vao->Unbind();
+}
+
+void Creature::KillVAO() {
+       vao.reset();
 }
 
 void Creature::Draw(graphics::Viewport &viewport) {
-       vao.Bind();
-       vao.DrawTriangles(6 * 6);
+       if (!vao) return;
+       vao->Bind();
+       vao->DrawTriangles(6 * 6);
 }
 
 
@@ -451,12 +606,13 @@ void Spawn(Creature &c, world::Planet &p) {
 
        Genome genome;
        genome.properties.Strength() = { 2.0, 0.1 };
-       genome.properties.Stamina() = { 4.0, 0.1 };
+       genome.properties.Stamina() = { 2.0, 0.1 };
        genome.properties.Dexerty() = { 2.0, 0.1 };
        genome.properties.Intelligence() = { 1.0, 0.1 };
        genome.properties.Lifetime() = { 480.0, 60.0 };
        genome.properties.Fertility() = { 0.5, 0.03 };
-       genome.properties.Mutability() = { 1.0, 0.1 };
+       genome.properties.Mutability() = { 0.9, 0.1 };
+       genome.properties.Adaptability() = { 0.9, 0.1 };
        genome.properties.OffspringMass() = { 0.3, 0.02 };
 
        glm::dvec3 color_avg(0.0);
@@ -485,6 +641,10 @@ void Spawn(Creature &c, world::Planet &p) {
        genome.base_hue = { hsl.x, 0.01 };
        genome.base_saturation = { hsl.y, 0.01 };
        genome.base_lightness = { hsl.z, 0.01 };
+       // use opposite color as start highlight
+       genome.highlight_hue = { std::fmod(hsl.x + 0.5, 1.0), 0.01 };
+       genome.highlight_saturation = { 1.0 - hsl.y, 0.01 };
+       genome.highlight_lightness = { 1.0 - hsl.z, 0.01 };
 
        genome.Configure(c);
 }
@@ -511,9 +671,9 @@ void Genome::Configure(Creature &c) const {
                glm::clamp(base_lightness.FakeNormal(random.SNorm()), 0.0, 1.0)
        );
        glm::dvec3 highlight_color(
-               std::fmod(base_color.x + 0.5, 1.0),
-               1.0 - base_color.y,
-               1.0 - base_color.z
+               std::fmod(highlight_hue.FakeNormal(random.SNorm()) + 1.0, 1.0),
+               glm::clamp(highlight_saturation.FakeNormal(random.SNorm()), 0.0, 1.0),
+               glm::clamp(highlight_lightness.FakeNormal(random.SNorm()), 0.0, 1.0)
        );
        c.BaseColor(hsl2rgb(base_color));
        c.HighlightColor(hsl2rgb(highlight_color));
@@ -525,6 +685,7 @@ void Genome::Configure(Creature &c) const {
 void Split(Creature &c) {
        Creature *a = new Creature(c.GetSimulation());
        const Situation &s = c.GetSituation();
+       a->AddParent(c);
        a->Name(c.GetSimulation().Assets().name.Sequential());
        c.GetGenome().Configure(*a);
        for (const auto &cmp : c.GetComposition()) {
@@ -534,12 +695,13 @@ void Split(Creature &c) {
        // TODO: duplicate situation somehow
        a->GetSituation().SetPlanetSurface(
                s.GetPlanet(), s.Surface(),
-               s.Position() + glm::dvec3(0.0, a->Size() + 0.1, 0.0));
+               s.Position() + glm::dvec3(0.0, 0.55 * a->Size(), 0.0));
        a->BuildVAO();
-       std::cout << "[" << int(c.GetSimulation().Time()) << "s] "
+       std::cout << "[" << ui::TimeString(c.GetSimulation().Time()) << "] "
                << a->Name() << " was born" << std::endl;
 
        Creature *b = new Creature(c.GetSimulation());
+       b->AddParent(c);
        b->Name(c.GetSimulation().Assets().name.Sequential());
        c.GetGenome().Configure(*b);
        for (const auto &cmp : c.GetComposition()) {
@@ -548,9 +710,9 @@ void Split(Creature &c) {
        s.GetPlanet().AddCreature(b);
        b->GetSituation().SetPlanetSurface(
                s.GetPlanet(), s.Surface(),
-               s.Position() + glm::dvec3(0.0, b->Size() - 0.1, 0.0));
+               s.Position() - glm::dvec3(0.0, 0.55 * b->Size(), 0.0));
        b->BuildVAO();
-       std::cout << "[" << int(c.GetSimulation().Time()) << "s] "
+       std::cout << "[" << ui::TimeString(c.GetSimulation().Time()) << "] "
                << b->Name() << " was born" << std::endl;
 
        c.Die();
@@ -564,9 +726,13 @@ Memory::Memory(Creature &c)
 Memory::~Memory() {
 }
 
+void Memory::Erase() {
+       known_types.clear();
+}
+
 void Memory::Tick(double dt) {
        Situation &s = c.GetSituation();
-       if (s.OnSurface()) {
+       if (s.OnTile()) {
                TrackStay({ &s.GetPlanet(), s.Surface(), s.SurfacePosition() }, dt);
        }
 }
@@ -636,9 +802,9 @@ bool Situation::OnSurface() const noexcept {
 }
 
 bool Situation::OnTile() const noexcept {
+       if (type != PLANET_SURFACE) return false;
        glm::ivec2 t(planet->SurfacePosition(surface, state.pos));
-       return type == PLANET_SURFACE
-               && t.x >= 0 && t.x < planet->SideLength()
+       return t.x >= 0 && t.x < planet->SideLength()
                && t.y >= 0 && t.y < planet->SideLength();
 }
 
@@ -658,12 +824,26 @@ const world::TileType &Situation::GetTileType() const noexcept {
 
 void Situation::Move(const glm::dvec3 &dp) noexcept {
        state.pos += dp;
+       EnforceConstraints(state);
+}
+
+void Situation::Accelerate(const glm::dvec3 &dv) noexcept {
+       state.vel += dv;
+       EnforceConstraints(state);
+}
+
+void Situation::EnforceConstraints(State &s) noexcept {
        if (OnSurface()) {
-               // enforce ground constraint
                if (Surface() < 3) {
-                       state.pos[(Surface() + 2) % 3] = std::max(0.0, state.pos[(Surface() + 2) % 3]);
+                       if (s.pos[(Surface() + 2) % 3] < GetPlanet().Radius()) {
+                               s.pos[(Surface() + 2) % 3] = GetPlanet().Radius();
+                               s.vel[(Surface() + 2) % 3] = std::max(0.0, s.vel[(Surface() + 2) % 3]);
+                       }
                } else {
-                       state.pos[(Surface() + 2) % 3] = std::min(0.0, state.pos[(Surface() + 2) % 3]);
+                       if (s.pos[(Surface() + 2) % 3] > -GetPlanet().Radius()) {
+                               s.pos[(Surface() + 2) % 3] = -GetPlanet().Radius();
+                               s.vel[(Surface() + 2) % 3] = std::min(0.0, s.vel[(Surface() + 2) % 3]);
+                       }
                }
        }
 }
@@ -673,6 +853,7 @@ void Situation::SetPlanetSurface(world::Planet &p, int srf, const glm::dvec3 &po
        planet = &p;
        surface = srf;
        state.pos = pos;
+       EnforceConstraints(state);
 }
 
 
@@ -693,6 +874,13 @@ Steering::Steering(const Creature &c)
 Steering::~Steering() {
 }
 
+void Steering::Off() noexcept {
+       separating = false;
+       halting = false;
+       seeking = false;
+       arriving = false;
+}
+
 void Steering::Separate(double min_distance, double max_lookaround) noexcept {
        separating = true;
        min_dist = min_distance;
@@ -703,6 +891,10 @@ void Steering::DontSeparate() noexcept {
        separating = false;
 }
 
+void Steering::ResumeSeparate() noexcept {
+       separating = true;
+}
+
 void Steering::Halt() noexcept {
        halting = true;
        seeking = false;
@@ -740,46 +932,29 @@ glm::dvec3 Steering::Force(const Situation::State &s) const noexcept {
                                repulse += normalize(diff) * (1.0 - sep / min_dist);
                        }
                }
-               SumForce(result, repulse, force);
+               result += repulse;
        }
        if (halting) {
-               SumForce(result, s.vel * -force, force);
+               // break twice as hard
+               result += -2.0 * s.vel * force;
        }
        if (seeking) {
                glm::dvec3 diff = target - s.pos;
                if (!allzero(diff)) {
-                       SumForce(result, TargetVelocity(s, (normalize(diff) * speed), force), force);
+                       result += TargetVelocity(s, (normalize(diff) * speed), force);
                }
        }
        if (arriving) {
                glm::dvec3 diff = target - s.pos;
                double dist = length(diff);
                if (!allzero(diff) && dist > std::numeric_limits<double>::epsilon()) {
-                       SumForce(result, TargetVelocity(s, diff * std::min(dist * force, speed) / dist, force), force);
+                       result += TargetVelocity(s, diff * std::min(dist * force, speed) / dist, force);
                }
        }
-       return result;
-}
-
-bool Steering::SumForce(glm::dvec3 &out, const glm::dvec3 &in, double max) const noexcept {
-       if (allzero(in) || anynan(in)) {
-               return false;
-       }
-       double cur = allzero(out) ? 0.0 : length(out);
-       double rem = max - cur;
-       if (rem < 0.0) {
-               return true;
-       }
-       double add = length(in);
-       if (add > rem) {
-               // this method is off if in and out are in different
-               // directions, but gives okayish results
-               out += in * (1.0 / add);
-               return true;
-       } else {
-               out += in;
-               return false;
+       if (length2(result) > max_force * max_force) {
+               result = normalize(result) * max_force;
        }
+       return result;
 }
 
 glm::dvec3 Steering::TargetVelocity(const Situation::State &s, const glm::dvec3 &vel, double acc) const noexcept {