Added a second ship to the simulation.

Spacewar.c

@@ -1,4 +1,4 @@
-// SDL Experiment 12, Barra Ó Catháin.
+// SDL Experiment 13, Barra Ó Catháin.
 // ===================================
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_image.h>
@@ -7,12 +7,22 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+// A 2D vector:
 typedef struct xyVector
 {
 	double xComponent;
 	double yComponent;
 } xyVector;
 
+// A struct storing the needed data to draw a ship:
+typedef struct ship
+{
+	SDL_Rect rectangle;
+	xyVector position;
+	xyVector velocity;
+	xyVector gravity;
+} ship;
+
 // Calculate the vector from point A to point B:
 static inline void xyVectorBetweenPoints(long ax, long ay, long bx, long by, xyVector * vector)
 {
@@ -24,8 +34,11 @@ static inline void xyVectorBetweenPoints(long ax, long ay, long bx, long by, xyV
 static inline double normalizeXYVector(xyVector * vector)
 {
 	double magnitude = sqrt(pow(vector->xComponent, 2) + pow(vector->yComponent, 2));
+	if(magnitude != 0)
+	{
 		vector->xComponent /= magnitude;
 		vector->yComponent /= magnitude;
+	}
 	return magnitude;
 }
 
@@ -38,6 +51,7 @@ static inline double angleBetweenVectors(xyVector * vectorA, xyVector * vectorB)
 	return atan2(dotProduct, determinant) / 0.01745329;
 }
 
+// Rotate XY vector by a given number of degrees:
 static inline void rotateXYVector(xyVector * vector, double degrees)
 {
 	double xComponent = vector->xComponent, yComponent = vector->yComponent;
@@ -65,6 +79,7 @@ static inline void multiplyXYVector(xyVector * vector, double scalar)
 	vector->xComponent *= scalar;
 	vector->yComponent *= scalar;
 }
+
 void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32_t radius)
 {
 	const int32_t diameter = (radius * 2);
@@ -103,6 +118,57 @@ void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32
 	}
 }
 
+void calculateGravity(xyVector * starPosition, ship * shipUnderGravity)
+{
+	// Calculate the vector between the star and ship:
+	xyVectorBetweenPoints(shipUnderGravity->position.xComponent, shipUnderGravity->position.yComponent,
+						  starPosition->xComponent, starPosition->yComponent, &shipUnderGravity->gravity);
+		
+	// Make it into a unit vector:
+	double gravityMagnitude = normalizeXYVector(&shipUnderGravity->gravity);
+	double gravityAcceleration = 0;
+	
+	// Calculate the gravity between the star and ship:
+	if(gravityMagnitude != 0)
+	{
+		if(gravityMagnitude >= 116)
+		{
+			gravityAcceleration = 0.1 * (35000 / (pow(gravityMagnitude, 2)));
+		}
+		else
+		{
+			gravityAcceleration = 0;
+		}
+	}
+	else
+	{
+		gravityAcceleration = 1;
+	}
+	
+	if(gravityAcceleration < 0.01)
+	{
+		gravityAcceleration = 0.01;
+	}
+		
+	// Scale the vector:
+	multiplyXYVector(&shipUnderGravity->gravity, gravityAcceleration);	
+}
+
+// Create a ship with the given parameters:
+ship createShip(int width, int height, double positionX, double positionY, double velocityX, double velocityY)
+{
+	ship newShip;
+	newShip.rectangle.w = width;
+	newShip.rectangle.h = height;
+	newShip.position.xComponent = positionX;
+	newShip.position.yComponent = positionY;
+	newShip.velocity.xComponent = velocityX;
+	newShip.velocity.yComponent = velocityY;
+	newShip.gravity.xComponent = 0;
+	newShip.gravity.yComponent = 0;
+	return newShip;
+}
+
 int main(int argc, char ** argv)
 {
 	SDL_Event event;
@@ -112,7 +178,12 @@ int main(int argc, char ** argv)
 	long positionX = 512, positionY = 512, starPositionX = 0, starPositionY = 0;
 	double deltaTime = 0, gravityMagnitude = 0, gravityAcceleration = 0, frameAccumulator = 0;	
 	bool quit = false, rotatingClockwise = false, rotatingAnticlockwise = false, accelerating = false;
-	xyVector positionVector = {512, 512}, velocityVector = {1, 0}, gravityVector = {0, 0}, engineVector = {0.16, 0}, upVector = {0, 0.1};
+	xyVector positionVector = {512, 512}, velocityVector = {1, 0}, gravityVector = {0, 0},
+		engineVector = {0.04, 0}, upVector = {0, 0.1}, starPosition = {0, 0};
+
+	// Get the initial
+	ship shipA = createShip(32, 32, 512, 512, 1, 0);
+	ship shipB = createShip(32, 32, -512, -512, 0, 1);
 	
 	// Initialize the SDL library, video, sound, and input:
 	if (SDL_Init(SDL_INIT_EVERYTHING) != 0)
@@ -124,11 +195,6 @@ int main(int argc, char ** argv)
 	IMG_Init(IMG_INIT_PNG);
 	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "2");
 
-	// Create a rectangle to put the ship in:
-	SDL_Rect shipRect;
-	shipRect.w = 32;
-	shipRect.h = 32;
-	
 	// Create an SDL window and rendering context in that window:
 	SDL_Window * window = SDL_CreateWindow("SDL_TEST", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 700, 700, 0);
 	SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, rendererFlags);
@@ -137,11 +203,11 @@ int main(int argc, char ** argv)
 	SDL_Texture * idleTexture, * acceleratingTexture, * clockwiseTexture, * anticlockwiseTexture, * currentTexture,
 	    * acceleratingTexture2;
 	
-	idleTexture = IMG_LoadTexture(renderer, "./Experiment-12-Images/Ship-Idle.png");
-	clockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-12-Images/Ship-Clockwise.png");
-	acceleratingTexture = IMG_LoadTexture(renderer, "./Experiment-12-Images/Ship-Accelerating.png");
-	anticlockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-12-Images/Ship-Anticlockwise.png");
-	acceleratingTexture2 = IMG_LoadTexture(renderer, "./Experiment-12-Images/Ship-Accelerating-Frame-2.png");
+	idleTexture = IMG_LoadTexture(renderer, "./Experiment-13-Images/Ship-Idle.png");
+	clockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-13-Images/Ship-Clockwise.png");
+	acceleratingTexture = IMG_LoadTexture(renderer, "./Experiment-13-Images/Ship-Accelerating.png");
+	anticlockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-13-Images/Ship-Anticlockwise.png");
+	acceleratingTexture2 = IMG_LoadTexture(renderer, "./Experiment-13-Images/Ship-Accelerating-Frame-2.png");
 
 	// Enable resizing the window:
 	SDL_SetWindowResizable(window, SDL_TRUE);
@@ -222,62 +288,55 @@ int main(int argc, char ** argv)
             }
         }
 
-		// Wrap the position if the ship goes interstellar:
-		if(positionVector.xComponent > 4096)
+		// Wrap the positions if the ship goes interstellar:
+		if(shipA.position.xComponent > 4096)
 		{
-			positionVector.xComponent = -2000;
-			velocityVector.xComponent *= 0.9;
+			shipA.position.xComponent = -2000;
+			shipA.velocity.xComponent *= 0.9;
 		}
-		else if(positionVector.xComponent < -4096)
+		else if(shipA.position.xComponent < -4096)
 		{
-			positionVector.xComponent = 2000;
-			velocityVector.xComponent *= 0.9;
+			shipA.position.xComponent = 2000;
+			shipA.velocity.xComponent *= 0.9;
+		}
+		if(shipA.position.yComponent > 4096)
+		{
+			shipA.position.yComponent = -2000;
+			shipA.velocity.yComponent *= 0.9;
+		}
+		else if(shipA.position.yComponent < -4096)
+		{
+			shipA.position.yComponent = 2000;
+			shipA.velocity.yComponent *= 0.9;
 		}
 
-		if(positionVector.yComponent > 4096)
+		if(shipB.position.xComponent > 4096)
 		{
-			positionVector.yComponent = -2000;
-			velocityVector.yComponent *= 0.9;
+			shipB.position.xComponent = -2000;
+			shipB.velocity.xComponent *= 0.9;
 		}
-		else if(positionVector.yComponent < -4096)
+		else if(shipB.position.xComponent < -4096)
 		{
-			positionVector.yComponent = 2000;
-			velocityVector.yComponent *= 0.9;
+			shipB.position.xComponent = 2000;
+			shipB.velocity.xComponent *= 0.9;
+		}
+		if(shipB.position.yComponent > 4096)
+		{
+			shipB.position.yComponent = -2000;
+			shipB.velocity.yComponent *= 0.9;
+		}
+		else if(shipB.position.yComponent < -4096)
+		{
+			shipB.position.yComponent = 2000;
+			shipB.velocity.yComponent *= 0.9;
 		}
 		
         // Store the window's current width and height:
 		SDL_GetWindowSize(window, &width, &height);
 
-		// Calculate the vector between the star and ship:
-		xyVectorBetweenPoints(positionVector.xComponent, positionVector.yComponent, starPositionX, starPositionY, &gravityVector);
-		
-		// Make it into a unit vector:
-		gravityMagnitude = normalizeXYVector(&gravityVector);
-
-		// Calculate the gravity between the star and ship:
-		if(gravityMagnitude != 0)
-		{
-			if(gravityMagnitude >= 215)
-			{
-				gravityAcceleration = 10 * (9000 / (pow(gravityMagnitude, 2)));
-			}
-			else
-			{
-				gravityAcceleration = 0.5 * (5000 / (pow(gravityMagnitude, 2)));
-			}
-		}
-		else
-		{
-			gravityAcceleration = 1;
-		}
-
-		if(gravityAcceleration < 0.01)
-		{
-			gravityAcceleration = 0.01;
-		}
-		
-		// Scale the vector:
-		multiplyXYVector(&gravityVector, gravityAcceleration);
+		// Calculate the gravity for the ships:
+		calculateGravity(&starPosition, &shipA);
+		calculateGravity(&starPosition, &shipB);
 		
 		// Set the texture to idle:
 		currentTexture = idleTexture;
@@ -295,10 +354,12 @@ int main(int argc, char ** argv)
 		}
 		
 		// Calculate the new current velocity:
-		addXYVectorDeltaScaled(&velocityVector, &gravityVector, deltaTime);
+		addXYVectorDeltaScaled(&shipA.velocity, &shipA.gravity, deltaTime);
+		addXYVectorDeltaScaled(&shipB.velocity, &shipB.gravity, deltaTime);
+		
 		if(accelerating)
 		{
-			addXYVectorDeltaScaled(&velocityVector, &engineVector, deltaTime);
+			addXYVectorDeltaScaled(&shipA.velocity, &engineVector, deltaTime);
 			frameAccumulator += deltaTime;
 			currentTexture = acceleratingTexture;
 			if((long)frameAccumulator % 4)
@@ -308,14 +369,15 @@ int main(int argc, char ** argv)
 		}
 		
 		// Calculate the new position:
-		addXYVectorDeltaScaled(&positionVector, &velocityVector, deltaTime);
+		addXYVectorDeltaScaled(&shipA.position, &shipA.velocity, deltaTime);
+		addXYVectorDeltaScaled(&shipB.position, &shipB.velocity, deltaTime);
 		
-		positionX = (long)positionVector.xComponent;
-		positionY = (long)positionVector.yComponent;
+		// Calculate the position of the sprites:
+		shipA.rectangle.x = (width/2) - 16;
+		shipA.rectangle.y = (height/2) - 16;
 
-		// Calculate the position of the sprite:
-		shipRect.x = (width/2) - 15;
-		shipRect.y = (height/2) - 15;
+		shipB.rectangle.x = (long)(((shipB.position.xComponent - shipA.position.xComponent) - 32) + width/2);
+		shipB.rectangle.y = (long)(((shipB.position.yComponent - shipA.position.yComponent) - 32) + height/2);
 		
 		// Set the colour to black:
 		SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
@@ -324,28 +386,32 @@ int main(int argc, char ** argv)
 		SDL_RenderClear(renderer);
 
 		// Draw the ship:
-		SDL_RenderCopyEx(renderer, currentTexture, NULL, &shipRect, angleBetweenVectors(&engineVector, &upVector) + 90, NULL, 0);
+		SDL_RenderCopyEx(renderer, currentTexture, NULL, &shipA.rectangle,
+						 angleBetweenVectors(&engineVector, &upVector) + 90, NULL, 0);
+		SDL_RenderCopyEx(renderer, currentTexture, NULL, &shipB.rectangle,
+						 angleBetweenVectors(&shipB.velocity, &upVector) + 90, NULL, 0);
 		
 		// Set the colour to yellow:
 		SDL_SetRenderDrawColor(renderer, 255, 255, 0, 255);
 
 		// Draw a circle as the star:
-		DrawCircle(renderer, (long)(starPositionX - positionX) + width/2, (long)(starPositionY - positionY) + height/2 , 200);
+		DrawCircle(renderer, (long)(starPositionX - shipA.position.xComponent) + width/2,
+				   (long)(starPositionY - shipA.position.yComponent) + height/2, 50);
 
 		// Draw a line representing the velocity:
 		SDL_RenderDrawLine(renderer, width/2, height/2,
-						   (long)((width/2) + velocityVector.xComponent * 15),
-	   					   (long)((height/2) + velocityVector.yComponent * 15));
+						   (long)((width/2) + shipA.velocity.xComponent * 15),
+	   					   (long)((height/2) + shipA.velocity.yComponent * 15));
 
 		// Set the colour to blue:
 		SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);
 
 		// Draw a line representing the direction of the star:
-		normalizeXYVector(&gravityVector);
-		multiplyXYVector(&gravityVector, 100);
+		normalizeXYVector(&shipA.gravity);
+		multiplyXYVector(&shipA.gravity, 100);
 		SDL_RenderDrawLine(renderer, width/2, height/2,
-						   (long)((width/2) + gravityVector.xComponent),
-						   (long)((height/2) + gravityVector.yComponent));
+						   (long)((width/2) + shipA.gravity.xComponent),
+						   (long)((height/2) + shipA.gravity.yComponent));
 
 		// Present the rendered graphics:
 		SDL_RenderPresent(renderer);
@@ -354,5 +420,5 @@ int main(int argc, char ** argv)
 }
 // ===========================================================================================
 // Local Variables:
-// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-12.c -lSDL2_image -lm" 
+// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-13.c -lSDL2_image -lm" 
 // End: