first pass rope system

samples/golf/golf.vcxproj

@@ -676,6 +676,7 @@
     <ClCompile Include="src\golf\ProgressIcon.cpp" />
     <ClCompile Include="src\golf\PropFollowSystem.cpp" />
     <ClCompile Include="src\golf\RayResultCallback.cpp" />
+    <ClCompile Include="src\golf\RopeSystem.cpp" />
     <ClCompile Include="src\golf\server\EightballDirector.cpp" />
     <ClCompile Include="src\golf\server\NineballDirector.cpp" />
     <ClCompile Include="src\golf\server\Server.cpp" />
@@ -826,6 +827,7 @@
     <ClInclude Include="src\golf\PuttingState.hpp" />
     <ClInclude Include="src\golf\RandNames.hpp" />
     <ClInclude Include="src\golf\RayResultCallback.hpp" />
+    <ClInclude Include="src\golf\RopeSystem.hpp" />
     <ClInclude Include="src\golf\ScoreStrings.hpp" />
     <ClInclude Include="src\golf\ScoreType.hpp" />
     <ClInclude Include="src\golf\server\BilliardsDirector.hpp" />

samples/golf/golf.vcxproj.filters

@@ -507,6 +507,9 @@
     <ClCompile Include="src\golf\TimeOfDay.cpp">
       <Filter>Source Files\golf\client\time of day</Filter>
     </ClCompile>
+    <ClCompile Include="src\golf\RopeSystem.cpp">
+      <Filter>Source Files\golf\client\systems</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="src\ErrorCheck.hpp">
@@ -1040,6 +1043,9 @@
     <ClInclude Include="src\golf\TimeOfDay.hpp">
       <Filter>Header Files\golf\client\time of day</Filter>
     </ClInclude>
+    <ClInclude Include="src\golf\RopeSystem.hpp">
+      <Filter>Header Files\golf\client\systems</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <None Include="src\golf\OptionsEnum.inl">

samples/golf/src/golf/CMakeLists.txt

@@ -81,6 +81,7 @@ set(GOLF_SRC
   #${PROJECT_DIR}/golf/PuttingState.cpp
   #${PROJECT_DIR}/golf/PuttingStateUI.cpp
   ${PROJECT_DIR}/golf/RayResultCallback.cpp
+  ${PROJECT_DIR}/golf/RopeSystem.cpp
   ${PROJECT_DIR}/golf/SharedStateData.cpp
   ${PROJECT_DIR}/golf/SoundEffectsDirector.cpp
   ${PROJECT_DIR}/golf/SpectatorSystem.cpp

samples/golf/src/golf/RopeSystem.cpp

@@ -0,0 +1,192 @@
+/*-----------------------------------------------------------------------
+
+Matt Marchant 2024
+http://trederia.blogspot.com
+
+Super Video Golf - zlib licence.
+
+This software is provided 'as-is', without any express or
+implied warranty.In no event will the authors be held
+liable for any damages arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute
+it freely, subject to the following restrictions :
+
+1. The origin of this software must not be misrepresented;
+you must not claim that you wrote the original software.
+If you use this software in a product, an acknowledgment
+in the product documentation would be appreciated but
+is not required.
+
+2. Altered source versions must be plainly marked as such,
+and must not be misrepresented as being the original software.
+
+3. This notice may not be removed or altered from any
+source distribution.
+
+-----------------------------------------------------------------------*/
+
+#include "RopeSystem.hpp"
+
+#include <crogine/ecs/Scene.hpp>
+#include <crogine/ecs/components/Transform.hpp>
+
+namespace
+{
+    constexpr glm::vec3 Gravity(0.f, -9.f, 0.f);
+}
+
+RopeSystem::RopeSystem(cro::MessageBus& mb)
+    : cro::System(mb, typeid(RopeSystem))
+{
+    requireComponent<cro::Transform>();
+    requireComponent<RopeNode>();
+}
+
+//public
+void RopeSystem::process(float dt)
+{
+    for (auto& rope : m_ropes)
+    {
+        rope.simulate(dt);
+    }
+}
+
+std::size_t RopeSystem::addRope(glm::vec3 start, glm::vec3 end, float slack)
+{
+    auto ret = m_ropes.size();
+    m_ropes.emplace_back(start, end, slack, *getScene());
+
+    return ret;
+}
+
+//private
+void RopeSystem::onEntityAdded(cro::Entity e)
+{
+    const auto& node = e.getComponent<RopeNode>();
+    if (node.ropeID < m_ropes.size())
+    {
+        m_ropes[node.ropeID].addNode(e);
+    }
+    else
+    {
+        LogW << "Tried adding node to rope " << node.ropeID << " which doesn't exist." << std::endl;
+        getScene()->destroyEntity(e);
+    }
+}
+
+void RopeSystem::onEntityRemoved(cro::Entity e)
+{
+    const auto& node = e.getComponent<RopeNode>();
+    CRO_ASSERT(node.ropeID < m_ropes.size());
+
+    m_ropes[node.ropeID].removeNode(e);
+}
+
+
+//-------rope class-------//
+Rope::Rope(glm::vec3 start, glm::vec3 end, float /*slack*/, cro::Scene& scene)
+    : m_nodeSpacing(0.f)
+{
+    auto ent = scene.createEntity();
+    ent.addComponent<cro::Transform>();
+    ent.addComponent<RopeNode>().position = start;
+    ent.getComponent<RopeNode>().prevPosition = start;
+    m_nodes.push_back(ent);
+
+    ent = scene.createEntity();
+    ent.addComponent<cro::Transform>();
+    ent.addComponent<RopeNode>().position = end;
+    ent.getComponent<RopeNode>().prevPosition = end;
+    m_nodes.push_back(ent);
+
+    //this always pins the first and last point
+    //as it's possible that the entities may get removed
+    recalculate();
+}
+
+//public
+void Rope::addNode(cro::Entity e)
+{
+    m_nodes.push_back(e);
+    recalculate();
+}
+
+void Rope::removeNode(cro::Entity e)
+{
+    m_nodes.erase(std::remove_if(m_nodes.begin(), m_nodes.end(), 
+        [e](cro::Entity ent)
+        {
+            return e == ent;
+        }), m_nodes.end());
+    recalculate();
+}
+
+void Rope::simulate(float dt)
+{
+    if (m_nodes.size() > 2)
+    {
+        integrate(dt);
+        constrain();
+    }
+}
+
+//private
+void Rope::recalculate()
+{
+    if (!m_nodes.empty())
+    {
+        if (m_nodes.size() > 1)
+        {
+            auto position = m_nodes.front().getComponent<RopeNode>().position;
+            auto stride = m_nodes.back().getComponent<RopeNode>().position - position;
+
+            if (glm::length2(stride) != 0)
+            {
+                float len = glm::length(stride) + 0.001f;
+
+                //TODO add any slack we want to stride
+                //which should be a RATIO not a fixed length
+                m_nodeSpacing = len;
+
+                stride = glm::normalize(stride) * (len / (m_nodes.size() - 1));
+            }
+
+            for (auto node : m_nodes)
+            {
+                auto& n = node.getComponent<RopeNode>();
+                n.position = position;
+                n.prevPosition = position;
+                n.force = glm::vec3(0.f);
+                n.fixed = false;
+            }
+        }
+
+        m_nodes.front().getComponent<RopeNode>().fixed = true;
+        m_nodes.back().getComponent<RopeNode>().fixed = true;
+    }    
+}
+
+void Rope::integrate(float dt)
+{
+    for (auto node : m_nodes)
+    {
+        auto& n = node.getComponent<RopeNode>();
+        //this means we're delayed one frame, but it has to happen
+        //after we apply the constraints from the previous integration
+        node.getComponent<cro::Transform>().setPosition(n.position);
+
+        if (!n.fixed)
+        {
+            auto old = n.position;
+            n.position = 2.f * n.position - n.prevPosition + ((n.force + Gravity) * dt * dt);
+            n.prevPosition = old;
+        }
+    }
+}
+
+void Rope::constrain()
+{
+    static constexpr std::size_t MaxIterations = 30;
+}

samples/golf/src/golf/RopeSystem.hpp

@@ -0,0 +1,103 @@
+/*-----------------------------------------------------------------------
+
+Matt Marchant 2024
+http://trederia.blogspot.com
+
+Super Video Golf - zlib licence.
+
+This software is provided 'as-is', without any express or
+implied warranty.In no event will the authors be held
+liable for any damages arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute
+it freely, subject to the following restrictions :
+
+1. The origin of this software must not be misrepresented;
+you must not claim that you wrote the original software.
+If you use this software in a product, an acknowledgment
+in the product documentation would be appreciated but
+is not required.
+
+2. Altered source versions must be plainly marked as such,
+and must not be misrepresented as being the original software.
+
+3. This notice may not be removed or altered from any
+source distribution.
+
+-----------------------------------------------------------------------*/
+
+#pragma once
+
+#include <crogine/ecs/System.hpp>
+
+//component on an entity, used to
+//update the entity final position
+struct RopeNode final
+{
+    glm::vec3 position = glm::vec3(0.f);
+    glm::vec3 prevPosition = glm::vec3(0.f);
+    bool fixed = false;
+
+    //ID of the rope to which this node
+    //will belong. Must be valid when ent
+    //is created, editing afterwards has
+    //no effect. ID is returned from
+    //RopeSystem::addRope();
+    std::size_t ropeID = std::numeric_limits<std::size_t>::max();
+
+    //any external force added to this node
+    glm::vec3 force = glm::vec3(0.f);
+};
+
+//represents a collection of nodes in
+//a single verlet simulation. Multiple of
+//these may exist in the system
+class Rope final
+{
+public:
+    Rope(glm::vec3 start, glm::vec3 end, float slack, cro::Scene&);
+
+    void addNode(cro::Entity);
+
+    //TODO it's possible to destroy entities outside
+    //of this system - this func just tidies up loose
+    //references - I have no idea how it'll behave though...
+    void removeNode(cro::Entity);
+
+    void simulate(float);
+
+private:
+
+    //we iterate over these in he simaultion rather than the system's entity list
+    std::vector<cro::Entity> m_nodes;
+    float m_nodeSpacing;
+    void recalculate(); //called when adding a new node
+
+    void integrate(float dt);
+    void constrain();
+};
+
+class RopeSystem final : public cro::System
+{
+public:
+    explicit RopeSystem(cro::MessageBus&);
+
+    void process(float) override;
+
+    //creates a new rope between the given fixed points.
+    //returns an ID to use with components when assigning
+    //those entities to a specific rope.
+    //increase slack for a looser rope between fixed points
+    std::size_t addRope(glm::vec3, glm::vec3, float slack = 0.f);
+
+private:
+    std::vector<Rope> m_ropes;
+
+    //validates the rope in the component ID
+    //exists and adds it to the rop if it does
+    void onEntityAdded(cro::Entity) override;
+
+    //removes the entity from a rope
+    void onEntityRemoved(cro::Entity) override;
+};