Add acceleration to movement code

Dengine.vcxproj

@@ -140,6 +140,7 @@
     <ClInclude Include="src\include\Dengine\Common.h" />
     <ClInclude Include="src\include\Breakout\Game.h" />
     <ClInclude Include="src\include\Dengine\Entity.h" />
+    <ClInclude Include="src\include\Dengine\Math.h" />
     <ClInclude Include="src\include\Dengine\OpenGL.h" />
     <ClInclude Include="src\include\Dengine\Renderer.h" />
     <ClInclude Include="src\include\Dengine\Shader.h" />

Dengine.vcxproj.filters

@@ -74,5 +74,8 @@
     <ClInclude Include="src\include\Dengine\Entity.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="src\include\Dengine\Math.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

src/Entity.cpp

@@ -6,6 +6,7 @@ namespace Dengine
 
 Entity::Entity()
 : pos(glm::vec2(0, 0))
+, dPos(glm::vec2(0, 0))
 , size(glm::vec2(0, 0))
 , tex(nullptr)
 {
@@ -14,6 +15,7 @@ Entity::Entity()
 Entity::Entity(const glm::vec2 pos, const Texture *tex)
 {
 	this->pos  = pos;
+	this->dPos = glm::vec2(0, 0);
 	this->tex  = tex;
 	this->size = glm::vec2(tex->getWidth(), tex->getHeight());
 }
@@ -21,6 +23,7 @@ Entity::Entity(const glm::vec2 pos, const Texture *tex)
 Entity::Entity(const glm::vec2 pos, glm::vec2 size, const Texture *tex)
 {
 	this->pos  = pos;
+	this->dPos = glm::vec2(0, 0);
 	this->tex  = tex;
 	this->size = size;
 }
@@ -29,6 +32,7 @@ Entity::Entity(const glm::vec2 pos, const std::string texName)
 {
 	Texture *tex = AssetManager::getTexture(texName);
 	this->pos  = pos;
+	this->dPos = glm::vec2(0, 0);
 	this->tex  = tex;
 	this->size = glm::vec2(tex->getWidth(), tex->getHeight());
 

src/WorldTraveller.cpp

@@ -64,27 +64,60 @@ void Game::init()
 
 void Game::update(const f32 dt)
 {
-	const f32 heroSpeed = static_cast<f32>((3.0f * METERS_TO_PIXEL) * dt);
+	/*
+	   Equations of Motion
+	   f(t)  = position     m
+	   f'(t) = velocity     m/s
+	   f"(t) = acceleration m/s^2
+
+	   The user supplies an acceleration, a, and by integrating
+	   f"(t) = a,                   where a is a constant, acceleration
+	   f'(t) = a*t + v,             where v is a constant, old velocity
+	   f (t) = (a/2)*t^2 + v*t + p, where p is a constant, old position
+	 */
+
+	glm::vec2 ddPos = glm::vec2(0, 0);
 
 	if (this->keys[GLFW_KEY_SPACE])
 	{
-#if 0
-		Dengine::Entity hitMarker = Dengine::Entity(glm::vec2(0, 0), "hitMarker");
-		glm::vec2 hitMarkerP =
-		    glm::vec2((hero.pos.x * 1.5f) + hitMarker.tex->getWidth(), hero.pos.y * 1.5f);
-		hitMarker.pos = hitMarkerP;
-		renderer->drawEntity(&hitMarker);
-#endif
 	}
 
 	if (this->keys[GLFW_KEY_RIGHT])
 	{
-		hero.pos.x += heroSpeed;
+		ddPos.x = 1.0f;
 	}
-	else if (this->keys[GLFW_KEY_LEFT])
+	if (this->keys[GLFW_KEY_LEFT])
 	{
-		hero.pos.x -= heroSpeed;
+		ddPos.x = -1.0f;
 	}
+
+	if (this->keys[GLFW_KEY_UP])
+	{
+		ddPos.y = 1.0f;
+	}
+	if (this->keys[GLFW_KEY_DOWN])
+	{
+		ddPos.y = -1.0f;
+	}
+
+	if (ddPos.x != 0.0f && ddPos.y != 0.0f)
+	{
+		// NOTE(doyle): Cheese it and pre-compute the vector for diagonal using
+		// pythagoras theorem on a unit triangle
+		// 1^2 + 1^2 = c^2
+		ddPos *= 0.70710678118f;
+	}
+
+	const f32 heroSpeed = static_cast<f32>((22.0f * METERS_TO_PIXEL)); // m/s^2
+	ddPos *= heroSpeed;
+
+	// TODO(doyle): Counteracting force on player's acceleration is arbitrary
+	ddPos += -(5.5f * hero.dPos);
+
+	glm::vec2 newHeroP = (0.5f * ddPos) * Dengine::Math::squared(dt) + (hero.dPos * dt) + hero.pos;
+
+	hero.dPos = (ddPos * dt) + hero.dPos;
+	hero.pos = newHeroP;
 }
 
 void Game::render()

src/include/Dengine/Entity.h

@@ -17,7 +17,10 @@ public:
 	Entity(const glm::vec2 pos, const std::string texName);
 	~Entity();
 
-	glm::vec2 pos;
+
+	glm::vec2 pos;  // Position
+	glm::vec2 dPos; // Velocity
+
 	glm::vec2 size;
 	const Texture *tex;
 };

src/include/Dengine/Math.h

@@ -0,0 +1,19 @@
+#ifndef DENGINE_MATH_H
+#define DENGINE_MATH_H
+
+#include <Dengine/Common.h>
+
+namespace Dengine
+{
+class Math
+{
+public:
+	static inline f32 squared(const f32 a)
+	{
+		f32 result = a * a;
+		return result;
+	}
+};
+}
+#endif
+

src/include/WorldTraveller/WorldTraveller.h

@@ -1,17 +1,18 @@
 #ifndef WORLDTRAVELLER_GAME_H
 #define WORLDTRAVELLER_GAME_H
 
-#include <Dengine/OpenGL.h>
+#include <Dengine/AssetManager.h>
 #include <Dengine/Common.h>
+#include <Dengine/Entity.h>
+#include <Dengine/Math.h>
+#include <Dengine/OpenGL.h>
 #include <Dengine/Renderer.h>
 #include <Dengine/Shader.h>
-#include <Dengine/AssetManager.h>
-#include <Dengine/Entity.h>
 
 namespace WorldTraveller
 {
 GLOBAL_VAR const i32 NUM_KEYS = 1024;
-GLOBAL_VAR const i32 METERS_TO_PIXEL = 100;
+GLOBAL_VAR const f32 METERS_TO_PIXEL = 100;
 
 enum Cardinal
 {