425 lines
12 KiB
C
425 lines
12 KiB
C
// SDL Experiment 14, Barra Ó Catháin.
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// ===================================
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#include <SDL2/SDL.h>
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#include <SDL2/SDL_image.h>
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#include <SDL2/SDL_timer.h>
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#include <math.h>
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#include <stdbool.h>
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#include <stdint.h>
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// A 2D vector:
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typedef struct xyVector
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{
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double xComponent;
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double yComponent;
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} xyVector;
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// A struct storing the needed data to draw a ship:
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typedef struct ship
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{
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SDL_Rect rectangle;
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xyVector position;
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xyVector velocity;
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xyVector gravity;
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} ship;
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// Calculate the vector from point A to point B:
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static inline void xyVectorBetweenPoints(long ax, long ay, long bx, long by, xyVector * vector)
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{
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vector->xComponent = bx - ax;
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vector->yComponent = by - ay;
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}
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// Normalize a vector, returning the magnitude:
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static inline double normalizeXYVector(xyVector * vector)
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{
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double magnitude = sqrt(pow(vector->xComponent, 2) + pow(vector->yComponent, 2));
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if(magnitude != 0)
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{
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vector->xComponent /= magnitude;
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vector->yComponent /= magnitude;
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}
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return magnitude;
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}
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// Get the angle between vectors:
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static inline double angleBetweenVectors(xyVector * vectorA, xyVector * vectorB)
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{
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double dotProduct = (vectorA->xComponent * vectorB->xComponent) + (vectorA->yComponent * vectorB->yComponent);
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double determinant = (vectorA->xComponent * vectorB->yComponent) - (vectorA->yComponent * vectorB->xComponent);
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return atan2(dotProduct, determinant) / 0.01745329;
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}
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// Rotate XY vector by a given number of degrees:
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static inline void rotateXYVector(xyVector * vector, double degrees)
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{
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double xComponent = vector->xComponent, yComponent = vector->yComponent;
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vector->xComponent = (cos(degrees * 0.01745329) * xComponent) - (sin(degrees * 0.01745329) * yComponent);
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vector->yComponent = (sin(degrees * 0.01745329) * xComponent) + (cos(degrees * 0.01745329) * yComponent);
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}
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// Add vector B to vector A:
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static inline void addXYVector(xyVector * vectorA, xyVector * vectorB)
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{
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vectorA->xComponent += vectorB->xComponent;
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vectorA->yComponent += vectorB->yComponent;
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}
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// Add vector B to vector A, scaled for units per frame:
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static inline void addXYVectorDeltaScaled(xyVector * vectorA, xyVector * vectorB, double deltaTime)
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{
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vectorA->xComponent += vectorB->xComponent * (0.001 * deltaTime) * 60;
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vectorA->yComponent += vectorB->yComponent * (0.001 * deltaTime) * 60;
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}
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// Multiply a vector by a scalar constant:
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static inline void multiplyXYVector(xyVector * vector, double scalar)
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{
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vector->xComponent *= scalar;
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vector->yComponent *= scalar;
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}
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void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32_t radius)
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{
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const int32_t diameter = (radius * 2);
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int32_t x = (radius - 1);
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int32_t y = 0;
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int32_t tx = 1;
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int32_t ty = 1;
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int32_t error = (tx - diameter);
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while (x >= y)
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{
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// Each of the following renders an octant of the circle
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SDL_RenderDrawPoint(renderer, centreX + x, centreY - y);
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SDL_RenderDrawPoint(renderer, centreX + x, centreY + y);
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SDL_RenderDrawPoint(renderer, centreX - x, centreY - y);
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SDL_RenderDrawPoint(renderer, centreX - x, centreY + y);
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SDL_RenderDrawPoint(renderer, centreX + y, centreY - x);
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SDL_RenderDrawPoint(renderer, centreX + y, centreY + x);
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SDL_RenderDrawPoint(renderer, centreX - y, centreY - x);
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SDL_RenderDrawPoint(renderer, centreX - y, centreY + x);
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if (error <= 0)
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{
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++y;
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error += ty;
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ty += 2;
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}
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if (error > 0)
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{
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--x;
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tx += 2;
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error += (tx - diameter);
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}
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}
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}
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void calculateGravity(xyVector * starPosition, ship * shipUnderGravity)
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{
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// Calculate the vector between the star and ship:
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xyVectorBetweenPoints(shipUnderGravity->position.xComponent, shipUnderGravity->position.yComponent,
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starPosition->xComponent, starPosition->yComponent, &shipUnderGravity->gravity);
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// Make it into a unit vector:
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double gravityMagnitude = normalizeXYVector(&shipUnderGravity->gravity);
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double gravityAcceleration = 0;
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// Calculate the gravity between the star and ship:
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if(gravityMagnitude != 0)
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{
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if(gravityMagnitude >= 116)
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{
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gravityAcceleration = 0.67 * (50000 / (pow(gravityMagnitude, 2)));
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}
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else
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{
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gravityAcceleration = 1;
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}
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}
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else
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{
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gravityAcceleration = 1;
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}
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if(gravityAcceleration < 0.01)
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{
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gravityAcceleration = 0.01;
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}
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// Scale the vector:
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multiplyXYVector(&shipUnderGravity->gravity, gravityAcceleration);
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}
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// Create a ship with the given parameters:
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ship createShip(int width, int height, double positionX, double positionY, double velocityX, double velocityY)
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{
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ship newShip;
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newShip.rectangle.w = width;
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newShip.rectangle.h = height;
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newShip.position.xComponent = positionX;
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newShip.position.yComponent = positionY;
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newShip.velocity.xComponent = velocityX;
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newShip.velocity.yComponent = velocityY;
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newShip.gravity.xComponent = 0;
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newShip.gravity.yComponent = 0;
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return newShip;
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}
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int main(int argc, char ** argv)
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{
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SDL_Event event;
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int width = 0, height = 0;
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uint32_t rendererFlags = SDL_RENDERER_ACCELERATED;
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uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0;
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long positionX = 512, positionY = 512, starPositionX = 0, starPositionY = 0;
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double deltaTime = 0, gravityMagnitude = 0, gravityAcceleration = 0, frameAccumulator = 0;
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bool quit = false, rotatingClockwise = false, rotatingAnticlockwise = false, accelerating = false;
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xyVector positionVector = {512, 512}, velocityVector = {1, 0}, gravityVector = {0, 0},
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engineVector = {0.04, 0}, upVector = {0, 0.1}, starPosition = {0, 0};
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// Get the initial
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ship shipA = createShip(32, 32, 512, 512, 1, 0);
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ship shipB = createShip(32, 32, -512, -512, 0, 1);
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// Initialize the SDL library, video, sound, and input:
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if (SDL_Init(SDL_INIT_EVERYTHING) != 0)
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{
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printf("SDL Initialization Error: %s\n", SDL_GetError());
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}
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// Initialize image loading:
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IMG_Init(IMG_INIT_PNG);
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SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "2");
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// Create an SDL window and rendering context in that window:
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SDL_Window * window = SDL_CreateWindow("SDL_TEST", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 700, 700, 0);
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SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, rendererFlags);
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SDL_SetWindowTitle(window, "Spacewar!");
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// Load in all of our textures:
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SDL_Texture * idleTexture, * acceleratingTexture, * clockwiseTexture, * anticlockwiseTexture, * currentTexture,
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* acceleratingTexture2;
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idleTexture = IMG_LoadTexture(renderer, "./Experiment-14-Images/Ship-Idle.png");
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clockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-14-Images/Ship-Clockwise.png");
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acceleratingTexture = IMG_LoadTexture(renderer, "./Experiment-14-Images/Ship-Accelerating.png");
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anticlockwiseTexture = IMG_LoadTexture(renderer, "./Experiment-14-Images/Ship-Anticlockwise.png");
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acceleratingTexture2 = IMG_LoadTexture(renderer, "./Experiment-14-Images/Ship-Accelerating-Frame-2.png");
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// Enable resizing the window:
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SDL_SetWindowResizable(window, SDL_TRUE);
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while (!quit)
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{
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lastFrameTime = thisFrameTime;
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thisFrameTime = SDL_GetPerformanceCounter();
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deltaTime = (double)(((thisFrameTime - lastFrameTime) * 1000) / (double)SDL_GetPerformanceFrequency());
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// Check if the user wants to quit:
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while (SDL_PollEvent(&event))
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{
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switch (event.type)
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{
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case SDL_QUIT:
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{
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quit = true;
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break;
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}
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case SDL_KEYDOWN:
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{
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switch (event.key.keysym.sym)
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{
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case SDLK_LEFT:
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{
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rotatingAnticlockwise = true;
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break;
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}
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case SDLK_RIGHT:
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{
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rotatingClockwise = true;
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break;
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}
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case SDLK_UP:
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{
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accelerating = true;
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break;
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}
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default:
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{
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break;
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}
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}
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break;
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}
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case SDL_KEYUP:
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{
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switch (event.key.keysym.sym)
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{
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case SDLK_LEFT:
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{
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rotatingAnticlockwise = false;
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break;
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}
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case SDLK_RIGHT:
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{
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rotatingClockwise = false;
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break;
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}
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case SDLK_UP:
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{
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accelerating = false;
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frameAccumulator = 0;
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break;
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}
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default:
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{
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break;
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}
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}
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break;
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}
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default:
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{
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break;
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}
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}
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}
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// Wrap the positions if the ship goes interstellar:
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if(shipA.position.xComponent > 4096)
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{
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shipA.position.xComponent = -2000;
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}
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else if(shipA.position.xComponent < -4096)
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{
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shipA.position.xComponent = 2000;
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}
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if(shipA.position.yComponent > 4096)
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{
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shipA.position.yComponent = -2000;
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}
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else if(shipA.position.yComponent < -4096)
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{
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shipA.position.yComponent = 2000;
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}
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if(shipB.position.xComponent > 4096)
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{
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shipB.position.xComponent = -2000;
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shipB.velocity.xComponent *= 0.9;
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}
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else if(shipB.position.xComponent < -4096)
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{
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shipB.position.xComponent = 2000;
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shipB.velocity.xComponent *= 0.9;
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}
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if(shipB.position.yComponent > 4096)
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{
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shipB.position.yComponent = -2000;
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shipB.velocity.yComponent *= 0.9;
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}
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else if(shipB.position.yComponent < -4096)
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{
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shipB.position.yComponent = 2000;
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shipB.velocity.yComponent *= 0.9;
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}
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// Store the window's current width and height:
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SDL_GetWindowSize(window, &width, &height);
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// Calculate the gravity for the ships:
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calculateGravity(&starPosition, &shipA);
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calculateGravity(&starPosition, &shipB);
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// Set the texture to idle:
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currentTexture = idleTexture;
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// Rotate the engine vector if needed:
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if(rotatingClockwise)
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{
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rotateXYVector(&engineVector, 0.25 * deltaTime);
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currentTexture = clockwiseTexture;
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}
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if(rotatingAnticlockwise)
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{
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rotateXYVector(&engineVector, -0.25 * deltaTime);
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currentTexture = anticlockwiseTexture;
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}
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// Calculate the new current velocity:
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addXYVectorDeltaScaled(&shipA.velocity, &shipA.gravity, deltaTime);
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addXYVectorDeltaScaled(&shipB.velocity, &shipB.gravity, deltaTime);
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if(accelerating)
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{
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addXYVectorDeltaScaled(&shipA.velocity, &engineVector, deltaTime);
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frameAccumulator += deltaTime;
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currentTexture = acceleratingTexture;
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if((long)frameAccumulator % 4)
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{
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currentTexture = acceleratingTexture2;
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}
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}
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// Calculate the new position:
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addXYVectorDeltaScaled(&shipA.position, &shipA.velocity, deltaTime);
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addXYVectorDeltaScaled(&shipB.position, &shipB.velocity, deltaTime);
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// Calculate the position of the sprites:
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shipA.rectangle.x = (width/2) - 16 - (shipA.velocity.xComponent * 15);
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shipA.rectangle.y = (height/2) - 16 - (shipA.velocity.yComponent * 15);
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shipB.rectangle.x = (long)((((shipB.position.xComponent - shipA.position.xComponent) - 32) + width/2) - (shipA.velocity.xComponent * 15));
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shipB.rectangle.y = (long)((((shipB.position.yComponent - shipA.position.yComponent) - 32) + height/2) - (shipA.velocity.yComponent * 15));
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// Set the colour to black:
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SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
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// Clear the screen, filling it with black:
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SDL_RenderClear(renderer);
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// Draw the ship:
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SDL_RenderCopyEx(renderer, currentTexture, NULL, &shipA.rectangle,
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angleBetweenVectors(&engineVector, &upVector) + 90, NULL, 0);
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SDL_RenderCopyEx(renderer, currentTexture, NULL, &shipB.rectangle,
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angleBetweenVectors(&shipB.velocity, &upVector) + 90, NULL, 0);
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// Set the colour to yellow:
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SDL_SetRenderDrawColor(renderer, 255, 255, 0, 255);
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// Draw a circle as the star:
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DrawCircle(renderer, (long)(starPositionX - shipA.position.xComponent) + width/2 - (shipA.velocity.xComponent * 15),
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(long)(starPositionY - shipA.position.yComponent) + height/2 - (shipA.velocity.yComponent * 15), 50);
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// Draw a line representing the velocity:
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SDL_RenderDrawLine(renderer, width/2 - (shipA.velocity.xComponent * 15),
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height/2 - (shipA.velocity.yComponent * 15),
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(long)((width/2) + shipA.velocity.xComponent * 15) - (shipA.velocity.xComponent * 15),
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(long)((height/2) + shipA.velocity.yComponent * 15) - (shipA.velocity.yComponent * 15));
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// Set the colour to blue:
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SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);
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// Draw a line representing the direction of the star:
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normalizeXYVector(&shipA.gravity);
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multiplyXYVector(&shipA.gravity, 100);
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SDL_RenderDrawLine(renderer,
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width/2 - (shipA.velocity.xComponent * 15),
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height/2 - (shipA.velocity.yComponent * 15),
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(width/2 - (shipA.velocity.xComponent * 15)) + shipA.gravity.xComponent,
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((height/2) - (shipA.velocity.yComponent * 15)) + shipA.gravity.yComponent);
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// Present the rendered graphics:
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SDL_RenderPresent(renderer);
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}
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return 0;
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}
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// ========================================================================================================
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// Local Variables:
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// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-14.c -lSDL2_image -lm -o 'Spacewar!'"
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// End:
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