Some small work on the fluid simulation

Apps/Liquefied/LiquefiedInterface.cpp

@@ -46,7 +46,7 @@ namespace Liq
 
     void LiquefiedInterface::AddBufferBar() const
     {
-        ImGui::SetNextWindowBgAlpha(0.9f);
+        ImGui::SetNextWindowBgAlpha(_windowAlphaValue);
         ImGui::SetNextWindowPos(_bufferBarPos, ImGuiCond_Always);
         ImGui::SetNextWindowSize(_bufferBarSize);
 

Engine/Physics/FluidSimulation/FluidSimulator.cpp

@@ -4,37 +4,66 @@ namespace Engine
 {
     // ----- Private -----
 
-    /* Applies forces to the liquid - just gravity in our case */
-    void FluidSimulator::AddForces(float dt)
+    /* Applies forces to the liquid - just gravity in our case. */
+    void FluidSimulator::AddForces(const float dt)
     {
-
+        for(uint32 x = 0; x < num_X; x++)
+        {
+            for(uint32 y = 0; y < num_Y; y++)
+            {
+                //Check for border cell
+                if(_s_staggered[x * num_Y + y] != 0.0f)
+                {
+                    _v_staggered[x * num_Y + y] += _gravity * dt;
+                }
+            }
+        }
     }
 
     /* Projection calculates and applies the right amount of pressure to make the       *
      * velocity field divergence-free and also enforces solid wall boundary conditions. */
-    void FluidSimulator::Project(float dt)
+    void FluidSimulator::Project(const float dt)
     {
 
     }
 
     /* Advection moves the quantity, or molecules, or particles, along the velocity field. */
-    void FluidSimulator::AdvectVelocity(float dt)
+    void FluidSimulator::AdvectVelocity(const float dt)
+    {
+
+    }
+
+    /* To visualize the flow, we store a density value at the center of each cell  *
+     * and advect it like the velocity field.                                      */
+    void FluidSimulator::AdvectSmoke(const float dt)
     {
 
     }
 
-    /* To visualize the flow, we store a density or dye value at the center of each cell  *
-     * and advect it like the velocity field.                                             */
-    void FluidSimulator::AdvectSmoke(float dt)
+    void FluidSimulator::Init()
     {
-
+        //Initialize border cells
+        for(uint32 x = 0; x < num_X; x++)
+        {
+            for(uint32 y = 0; y < num_Y; y++)
+            {
+                float cellValue = 1.0f; //Fluid cell
+
+                if((x == 0) || (y == 0) || (x == num_X - 1) || (y == num_Y - 1))
+                {
+                    cellValue = 0.0f; //Solid cell
+                }
+
+                _s_staggered[x * num_Y + y] = cellValue;
+            }
+        }
     }
 
     // ----- Public -----
 
     FluidSimulator::FluidSimulator()
     {
-
+        Init();
     }
 
     FluidSimulator::~FluidSimulator()

Engine/Physics/FluidSimulation/FluidSimulator.hpp

@@ -3,21 +3,32 @@
 #include "Window.hpp"
 #include "GlobalParams.hpp"
 
-#define at(x, y) ((x) * Liquiedfied::Params::SIMULATION_HEIGHT + (y))
+#define num_X LiquiefiedParams::SIMULATION_WIDTH
+#define num_Y LiquiefiedParams::SIMULATION_HEIGHT
 
 namespace Engine
 {
     class FluidSimulator
     {
         private:
             float _gravity = -9.81f;
-            float _velocityField[LiquiefiedParams::LIQUID_NUM_CELLS] = {0};
-            float _smokeField[LiquiefiedParams::LIQUID_NUM_CELLS]    = {0};
+
+            //Horizontal u-component is sampled at the centers of the vertical cell faces.
+            float _u_staggered[LiquiefiedParams::LIQUID_NUM_CELLS] = {0.0f};
+
+            //Vertical v-component is sampled at the centers of the horizontal cell faces.
+            float _v_staggered[LiquiefiedParams::LIQUID_NUM_CELLS] = {0.0f};
+
+            //s-component gets set to 0 for border cells.
+            float _s_staggered[LiquiefiedParams::LIQUID_NUM_CELLS] = {0.0f};
+
+            float _smokeField[LiquiefiedParams::LIQUID_NUM_CELLS]  = {0.0f};
 
             void AddForces(float dt);
             void Project(float dt);
             void AdvectVelocity(float dt);
             void AdvectSmoke(float dt);
+            void Init();
 
         public:
             FluidSimulator();