From eeb01452fe46fcb5efdc9c34b660305262097ca4 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Wed, 10 Dec 2025 11:26:13 +0100
Subject: Dangling changes

---
 lib/core/c++/particle/particle.hpp | 22 ++++++++++++++++++++++
 lib/core/tests/particles.cpp       | 25 ++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 3 deletions(-)

(limited to 'lib/core')

diff --git a/lib/core/c++/particle/particle.hpp b/lib/core/c++/particle/particle.hpp
index c87f15e..446e8a3 100644
--- a/lib/core/c++/particle/particle.hpp
+++ b/lib/core/c++/particle/particle.hpp
@@ -43,6 +43,28 @@ using Particle = Struct<
 >;
 }
 
+template<typename T,uint64_t D>
+constexpr auto verlet_step_lambda = [](saw::data<sch::Particle<T,D>>& particle, saw::data<T> time_step_delta){
+		auto& body = particle.template get<"rigid_body">();
+
+		auto& pos = body.template get<"position">();
+		auto& pos_old = body.template get<"position_old">();
+
+		// auto& rot = body.template get<"rotation">();
+		auto& acc = body.template get<"acceleration">();
+
+		auto tsd_squared = time_step_delta * time_step_delta;
+
+		saw::data<sch::Vector<T,D>> pos_new;
+		// Actual step
+		for(uint64_t i = 0u; i < D; ++i){
+			pos_new.at({{i}}) = saw::data<T>{2.0} * pos.at({{i}}) - pos_old.at({{i}}) + acc.at({{i}}) * tsd_squared;
+		}
+
+		pos_old = pos;
+		pos = pos_new;
+};
+
 template<typename T, uint64_t D, typename ParticleCollision = sch::ParticleMask<T,D> >
 class particle_system {
 private:
diff --git a/lib/core/tests/particles.cpp b/lib/core/tests/particles.cpp
index 277a8d0..60cdc14 100644
--- a/lib/core/tests/particles.cpp
+++ b/lib/core/tests/particles.cpp
@@ -10,6 +10,25 @@ using namespace kel::lbm::sch;
 
 using T = Float64;
 }
+SAW_TEST("Verlet step"){
+	using namespace kel;
+
+
+	saw::data<sch::Particle<sch::T,2u>> particle;
+	auto& body = particle.template get<"rigid_body">();
+	auto& pos = body.template get<"position">();
+	auto& pos_old = body.template get<"position_old">();
+
+	// auto& rot = body.template get<"rotation">();
+	auto& acc = body.template get<"acceleration">();
+
+	acc.at({{0}}).set({1.0});
+
+	lbm::verlet_step_lambda<sch::T,2u>(particle,{0.5});
+
+	SAW_EXPECT(pos.at({{0}}).get() == 0.25, std::string{"Incorrect Pos X: "} + std::to_string(pos.at({{0}}).get()));
+	SAW_EXPECT(pos.at({{1}}).get() == 0.0, std::string{"Incorrect Pos Y: "} + std::to_string(pos.at({{1}}).get()));
+}
 /*
 SAW_TEST("Minor Test for mask"){
 	using namespace kel;
@@ -31,8 +50,9 @@ SAW_TEST("Minor Test for mask"){
 	//saw::data<sch::Array<sch::T,2>> reference_mask{{{4+2,4+2}}};
 	//reference_mask.at({{0,0}});
 }
-
-SAW_TEST("Verlet integration test"){
+*/
+/*
+SAW_TEST("Verlet integration test 2D"){
 	using namespace kel;
 	lbm::particle_system<sch::T,2,sch::Particle<sch::T,2>> system;
 
@@ -79,7 +99,6 @@ SAW_TEST("Verlet integration test"){
 		}
 
 	}
-
 }
 */
 }
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