diff --git a/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Accelerating-Frame-2.png b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Accelerating-Frame-2.png new file mode 100644 index 0000000..ec49319 Binary files /dev/null and b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Accelerating-Frame-2.png differ diff --git a/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Accelerating.png b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Accelerating.png new file mode 100644 index 0000000..f9b2595 Binary files /dev/null and b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Accelerating.png differ diff --git a/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Anticlockwise.png b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Anticlockwise.png new file mode 100644 index 0000000..22268ea Binary files /dev/null and b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Anticlockwise.png differ diff --git a/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Clockwise.png b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Clockwise.png new file mode 100644 index 0000000..aa9989a Binary files /dev/null and b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Clockwise.png differ diff --git a/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Idle.png b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Idle.png new file mode 100644 index 0000000..b1c6cf6 Binary files /dev/null and b/SDL2-Bits-And-Pieces/Experiment-15/Experiment-15-Images/Ship-Idle.png differ diff --git a/SDL2-Bits-And-Pieces/Experiment-15/SDL2-Experiment-15-Client.c b/SDL2-Bits-And-Pieces/Experiment-15/SDL2-Experiment-15-Client.c new file mode 100644 index 0000000..849b7f1 --- /dev/null +++ b/SDL2-Bits-And-Pieces/Experiment-15/SDL2-Experiment-15-Client.c @@ -0,0 +1,228 @@ +// SDL Experiment 15, Barra Ó Catháin. +// =================================== +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +// 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; + int number; +} ship; + +// Get the angle between vectors: +static inline double angleBetweenVectors(xyVector * vectorA, xyVector * vectorB) +{ + double dotProduct = (vectorA->xComponent * vectorB->xComponent) + (vectorA->yComponent * vectorB->yComponent); + double determinant = (vectorA->xComponent * vectorB->yComponent) - (vectorA->yComponent * vectorB->xComponent); + + return atan2(dotProduct, determinant) / 0.01745329; +} + +void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32_t radius) +{ + const int32_t diameter = (radius * 2); + + int32_t x = (radius - 1); + int32_t y = 0; + int32_t tx = 1; + int32_t ty = 1; + int32_t error = (tx - diameter); + + while (x >= y) + { + // Each of the following renders an octant of the circle + SDL_RenderDrawPoint(renderer, centreX + x, centreY - y); + SDL_RenderDrawPoint(renderer, centreX + x, centreY + y); + SDL_RenderDrawPoint(renderer, centreX - x, centreY - y); + SDL_RenderDrawPoint(renderer, centreX - x, centreY + y); + SDL_RenderDrawPoint(renderer, centreX + y, centreY - x); + SDL_RenderDrawPoint(renderer, centreX + y, centreY + x); + SDL_RenderDrawPoint(renderer, centreX - y, centreY - x); + SDL_RenderDrawPoint(renderer, centreX - y, centreY + x); + + if (error <= 0) + { + ++y; + error += ty; + ty += 2; + } + + if (error > 0) + { + --x; + tx += 2; + error += (tx - diameter); + } + } +} + +int main(int argc, char ** argv) +{ + SDL_Event event; + bool quit = false; + int width = 0, height = 0; + uint32_t rendererFlags = SDL_RENDERER_ACCELERATED; + uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0; + long positionX = 512, positionY = 512, starPositionX = 0, starPositionY = 0; + xyVector positionVector = {512, 512}, velocityVector = {1, 0}, gravityVector = {0, 0}, + engineVector = {0.04, 0}, upVector = {0, 0.1}, starPosition = {0, 0}; + + // Create the socket: + int socketFileDesc = socket(AF_INET, SOCK_DGRAM, 0); + if (socketFileDesc < 0) + { + fprintf(stderr, "\tSocket Creation is:\t\033[33;40mRED.\033[0m Aborting launch.\n"); + exit(0); + } + printf("\tSocket Creation is:\t\033[32;40mGREEN.\033[0m\n"); + + // Make the socket timeout: + struct timeval read_timeout; + read_timeout.tv_sec = 0; + read_timeout.tv_usec = 10; + setsockopt(socketFileDesc, SOL_SOCKET, SO_RCVTIMEO, &read_timeout, sizeof read_timeout); + + // Create and fill the information needed to bind to the socket: + struct sockaddr_in serverAddress; + memset(&serverAddress, 0, sizeof(serverAddress)); + serverAddress.sin_family = AF_INET; // IPv4 + serverAddress.sin_addr.s_addr = INADDR_ANY; + serverAddress.sin_port = htons(12000); + + // Bind to the socket: + if (bind(socketFileDesc, (const struct sockaddr *)&serverAddress, sizeof(serverAddress)) < 0) + { + perror("bind failed"); + exit(EXIT_FAILURE); + } + + // Get the initial + ship shipA; + ship shipB; + + // Initialize the SDL library, video, sound, and input: + if (SDL_Init(SDL_INIT_EVERYTHING) != 0) + { + printf("SDL Initialization Error: %s\n", SDL_GetError()); + } + + // Initialize image loading: + IMG_Init(IMG_INIT_PNG); + SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "2"); + + // 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); + SDL_SetWindowTitle(window, "Spacewar!"); + + // Load in all of our textures: + SDL_Texture * idleTexture, * acceleratingTexture, * clockwiseTexture, * anticlockwiseTexture, * currentTexture, + * acceleratingTexture2; + + idleTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Idle.png"); + clockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Clockwise.png"); + acceleratingTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Accelerating.png"); + anticlockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Anticlockwise.png"); + acceleratingTexture2 = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Accelerating-Frame-2.png"); + + // Enable resizing the window: + SDL_SetWindowResizable(window, SDL_TRUE); + ship Temp; + bool shipAUpdated, shipBUpdated; + while (!quit) + { + while(!(shipAUpdated && shipBUpdated)) + { + // Receive data from the socket: + recvfrom(socketFileDesc, &Temp, sizeof(ship), 0, NULL, NULL); + if(Temp.number == 0) + { + shipA = Temp; + shipAUpdated = true; + } + if(Temp.number == 1) + { + shipB = Temp; + shipBUpdated = true; + } + } + + // Check if the user wants to quit: + while (SDL_PollEvent(&event)) + { + switch (event.type) + { + case SDL_QUIT: + { + quit = true; + break; + } + default: + { + break; + } + } + } + + // Store the window's current width and height: + SDL_GetWindowSize(window, &width, &height); + + // Set the texture to idle: + currentTexture = idleTexture; + + // Calculate the position of the sprites: + shipB.rectangle.x = (width/2) - 16 - (shipB.velocity.xComponent * 15); + shipB.rectangle.y = (height/2) - 16 - (shipB.velocity.yComponent * 15); + + shipA.rectangle.x = (long)((((shipA.position.xComponent - shipB.position.xComponent) - 32) + width/2) - (shipB.velocity.xComponent * 15)); + shipA.rectangle.y = (long)((((shipA.position.yComponent - shipB.position.yComponent) - 32) + height/2) - (shipB.velocity.yComponent * 15)); + + // Set the colour to black: + SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); + + // Clear the screen, filling it with black: + SDL_RenderClear(renderer); + + // Draw the ship: + SDL_RenderCopyEx(renderer, currentTexture, NULL, &shipA.rectangle, + angleBetweenVectors(&shipA.velocity, &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 - shipB.position.xComponent) + width/2 - (shipB.velocity.xComponent * 15), + (long)(starPositionY - shipB.position.yComponent) + height/2 - (shipB.velocity.yComponent * 15), 50); + + // Present the rendered graphics: + SDL_RenderPresent(renderer); + shipAUpdated = false; + shipBUpdated = false; + } + return 0; +} +// ======================================================================================================== +// Local Variables: +// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-15-Client.c -lSDL2_image -lm -o 'Spacewar Client!'" +// End: diff --git a/SDL2-Bits-And-Pieces/Experiment-15/SDL2-Experiment-15.c b/SDL2-Bits-And-Pieces/Experiment-15/SDL2-Experiment-15.c new file mode 100644 index 0000000..9f6caad --- /dev/null +++ b/SDL2-Bits-And-Pieces/Experiment-15/SDL2-Experiment-15.c @@ -0,0 +1,448 @@ +// SDL Experiment 15, Barra Ó Catháin. +// =================================== +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +// 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; + int number; +} ship; + +// Calculate the vector from point A to point B: +static inline void xyVectorBetweenPoints(long ax, long ay, long bx, long by, xyVector * vector) +{ + vector->xComponent = bx - ax; + vector->yComponent = by - ay; +} + +// Normalize a vector, returning the magnitude: +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; +} + +// Get the angle between vectors: +static inline double angleBetweenVectors(xyVector * vectorA, xyVector * vectorB) +{ + double dotProduct = (vectorA->xComponent * vectorB->xComponent) + (vectorA->yComponent * vectorB->yComponent); + double determinant = (vectorA->xComponent * vectorB->yComponent) - (vectorA->yComponent * vectorB->xComponent); + + 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; + vector->xComponent = (cos(degrees * 0.01745329) * xComponent) - (sin(degrees * 0.01745329) * yComponent); + vector->yComponent = (sin(degrees * 0.01745329) * xComponent) + (cos(degrees * 0.01745329) * yComponent); +} + +// Add vector B to vector A: +static inline void addXYVector(xyVector * vectorA, xyVector * vectorB) +{ + vectorA->xComponent += vectorB->xComponent; + vectorA->yComponent += vectorB->yComponent; +} + +// Add vector B to vector A, scaled for units per frame: +static inline void addXYVectorDeltaScaled(xyVector * vectorA, xyVector * vectorB, double deltaTime) +{ + vectorA->xComponent += vectorB->xComponent * (0.001 * deltaTime) * 60; + vectorA->yComponent += vectorB->yComponent * (0.001 * deltaTime) * 60; +} + +// Multiply a vector by a scalar constant: +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); + + int32_t x = (radius - 1); + int32_t y = 0; + int32_t tx = 1; + int32_t ty = 1; + int32_t error = (tx - diameter); + + while (x >= y) + { + // Each of the following renders an octant of the circle + SDL_RenderDrawPoint(renderer, centreX + x, centreY - y); + SDL_RenderDrawPoint(renderer, centreX + x, centreY + y); + SDL_RenderDrawPoint(renderer, centreX - x, centreY - y); + SDL_RenderDrawPoint(renderer, centreX - x, centreY + y); + SDL_RenderDrawPoint(renderer, centreX + y, centreY - x); + SDL_RenderDrawPoint(renderer, centreX + y, centreY + x); + SDL_RenderDrawPoint(renderer, centreX - y, centreY - x); + SDL_RenderDrawPoint(renderer, centreX - y, centreY + x); + + if (error <= 0) + { + ++y; + error += ty; + ty += 2; + } + + if (error > 0) + { + --x; + tx += 2; + error += (tx - diameter); + } + } +} + +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 = pow(2, (2500 / (pow(gravityMagnitude, 2)))) / 10; + } + else + { + gravityAcceleration = pow(2, (2500 / (pow(gravityMagnitude, 2)))) / 5; + } + } + 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, int number) +{ + 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; + newShip.number = number; + return newShip; +} + +int main(int argc, char ** argv) +{ + SDL_Event event; + int width = 0, height = 0; + uint32_t rendererFlags = SDL_RENDERER_ACCELERATED; + uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0; + 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 = {0.08, 0}, upVector = {0, 0.1}, starPosition = {0, 0}; + + // Create the socket: + int socketFileDesc = socket(AF_INET, SOCK_DGRAM, 0); + if (socketFileDesc < 0) + { + fprintf(stderr, "\tSocket Creation is:\t\033[33;40mRED.\033[0m Aborting launch.\n"); + exit(0); + } + printf("\tSocket Creation is:\t\033[32;40mGREEN.\033[0m\n"); + + // Create and fill the information needed to bind to the socket: + struct sockaddr_in serverAddress; + serverAddress.sin_family = AF_INET; // IPv4 + serverAddress.sin_addr.s_addr = inet_addr("127.0.0.1"); + serverAddress.sin_port = htons(12000); + + // Get the initial + ship shipA = createShip(32, 32, 512, 512, 1, 0, 0); + ship shipB = createShip(32, 32, -512, -512, 0, 1, 1); + + // Initialize the SDL library, video, sound, and input: + if (SDL_Init(SDL_INIT_EVERYTHING) != 0) + { + printf("SDL Initialization Error: %s\n", SDL_GetError()); + } + + // Initialize image loading: + IMG_Init(IMG_INIT_PNG); + SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "2"); + + // 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); + SDL_SetWindowTitle(window, "Spacewar!"); + + // Load in all of our textures: + SDL_Texture * idleTexture, * acceleratingTexture, * clockwiseTexture, * anticlockwiseTexture, * currentTexture, + * acceleratingTexture2; + + idleTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Idle.png"); + clockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Clockwise.png"); + acceleratingTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Accelerating.png"); + anticlockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Anticlockwise.png"); + acceleratingTexture2 = IMG_LoadTexture(renderer, "./Experiment-15-Images/Ship-Accelerating-Frame-2.png"); + + // Enable resizing the window: + SDL_SetWindowResizable(window, SDL_TRUE); + + while (!quit) + { + lastFrameTime = thisFrameTime; + thisFrameTime = SDL_GetPerformanceCounter(); + deltaTime = (double)(((thisFrameTime - lastFrameTime) * 1000) / (double)SDL_GetPerformanceFrequency()); + + // Check if the user wants to quit: + while (SDL_PollEvent(&event)) + { + switch (event.type) + { + case SDL_QUIT: + { + quit = true; + break; + } + case SDL_KEYDOWN: + { + switch (event.key.keysym.sym) + { + case SDLK_LEFT: + { + rotatingAnticlockwise = true; + break; + } + case SDLK_RIGHT: + { + rotatingClockwise = true; + break; + } + case SDLK_UP: + { + accelerating = true; + break; + } + default: + { + break; + } + } + break; + } + case SDL_KEYUP: + { + switch (event.key.keysym.sym) + { + case SDLK_LEFT: + { + rotatingAnticlockwise = false; + break; + } + case SDLK_RIGHT: + { + rotatingClockwise = false; + break; + } + case SDLK_UP: + { + accelerating = false; + frameAccumulator = 0; + break; + } + default: + { + break; + } + } + break; + } + default: + { + break; + } + } + } + + // Wrap the positions if the ship goes interstellar: + if(shipA.position.xComponent > 4096) + { + shipA.position.xComponent = -2000; + } + else if(shipA.position.xComponent < -4096) + { + shipA.position.xComponent = 2000; + } + if(shipA.position.yComponent > 4096) + { + shipA.position.yComponent = -2000; + } + else if(shipA.position.yComponent < -4096) + { + shipA.position.yComponent = 2000; + } + + if(shipB.position.xComponent > 4096) + { + shipB.position.xComponent = -2000; + shipB.velocity.xComponent *= 0.9; + } + else if(shipB.position.xComponent < -4096) + { + 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 gravity for the ships: + calculateGravity(&starPosition, &shipA); + calculateGravity(&starPosition, &shipB); + + // Set the texture to idle: + currentTexture = idleTexture; + + // Rotate the engine vector if needed: + if(rotatingClockwise) + { + rotateXYVector(&engineVector, 0.25 * deltaTime); + currentTexture = clockwiseTexture; + } + if(rotatingAnticlockwise) + { + rotateXYVector(&engineVector, -0.25 * deltaTime); + currentTexture = anticlockwiseTexture; + } + + // Calculate the new current velocity: + addXYVectorDeltaScaled(&shipA.velocity, &shipA.gravity, deltaTime); + addXYVectorDeltaScaled(&shipB.velocity, &shipB.gravity, deltaTime); + + if(accelerating) + { + addXYVectorDeltaScaled(&shipA.velocity, &engineVector, deltaTime); + frameAccumulator += deltaTime; + currentTexture = acceleratingTexture; + if((long)frameAccumulator % 4) + { + currentTexture = acceleratingTexture2; + } + } + + // Calculate the new position: + addXYVectorDeltaScaled(&shipA.position, &shipA.velocity, deltaTime); + addXYVectorDeltaScaled(&shipB.position, &shipB.velocity, deltaTime); + + // Calculate the position of the sprites: + shipA.rectangle.x = (width/2) - 16 - (shipA.velocity.xComponent * 15); + shipA.rectangle.y = (height/2) - 16 - (shipA.velocity.yComponent * 15); + + shipB.rectangle.x = (long)((((shipB.position.xComponent - shipA.position.xComponent) - 32) + width/2) - (shipA.velocity.xComponent * 15)); + shipB.rectangle.y = (long)((((shipB.position.yComponent - shipA.position.yComponent) - 32) + height/2) - (shipA.velocity.yComponent * 15)); + + // Set the colour to black: + SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); + + // Clear the screen, filling it with black: + SDL_RenderClear(renderer); + + // Draw the ship: + 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 - shipA.position.xComponent) + width/2 - (shipA.velocity.xComponent * 15), + (long)(starPositionY - shipA.position.yComponent) + height/2 - (shipA.velocity.yComponent * 15), 50); + + // Draw a line representing the velocity: + SDL_RenderDrawLine(renderer, width/2 - (shipA.velocity.xComponent * 15), + height/2 - (shipA.velocity.yComponent * 15), + (long)((width/2) + shipA.velocity.xComponent * 15) - (shipA.velocity.xComponent * 15), + (long)((height/2) + shipA.velocity.yComponent * 15) - (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(&shipA.gravity); + multiplyXYVector(&shipA.gravity, 100); + SDL_RenderDrawLine(renderer, + width/2 - (shipA.velocity.xComponent * 15), + height/2 - (shipA.velocity.yComponent * 15), + (width/2 - (shipA.velocity.xComponent * 15)) + shipA.gravity.xComponent, + ((height/2) - (shipA.velocity.yComponent * 15)) + shipA.gravity.yComponent); + + // Present the rendered graphics: + SDL_RenderPresent(renderer); + + sendto(socketFileDesc, &shipA, sizeof(ship), 0, (const struct sockaddr *)&serverAddress, sizeof(serverAddress)); + sendto(socketFileDesc, &shipB, sizeof(ship), 0, (const struct sockaddr *)&serverAddress, sizeof(serverAddress)); + } + return 0; +} +// ======================================================================================================== +// Local Variables: +// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-15.c -lSDL2_image -lm -o 'Spacewar!'" +// End: