diff --git a/SDL2-Bits-And-Pieces/SDL2-Experiment-07.c b/SDL2-Bits-And-Pieces/SDL2-Experiment-07.c new file mode 100644 index 0000000..463cfc2 --- /dev/null +++ b/SDL2-Bits-And-Pieces/SDL2-Experiment-07.c @@ -0,0 +1,215 @@ +// SDL Experiment 07, Barra Ó Catháin. +// =================================== +#include +#include +#include +#include +#include + +typedef struct xyVector +{ + double xComponent; + double yComponent; +} xyVector; + +// 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)); + vector->xComponent /= magnitude; + vector->yComponent /= magnitude; + return magnitude; +} + +// 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); + } + } +} + +int main(int argc, char ** argv) +{ + SDL_Event event; + bool quit = false; + int width = 0, height = 0; + uint32_t rendererFlags = SDL_RENDERER_ACCELERATED; + double deltaTime = 0, gravityMagnitude = 0, gravityAcceleration = 0; + uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0; + long positionX = 0, positionY = 0; + xyVector positionVector = {100, 100}, velocityVector = {20, 0}, gravityVector = {0, 0}; + + // Initialize the SDL library, video, sound, and input: + if (SDL_Init(SDL_INIT_EVERYTHING) != 0) + { + printf("SDL Initialization Error: %s\n", SDL_GetError()); + } + + // Create an SDL window and rendering context in that window: + SDL_Window * window = SDL_CreateWindow("SDL_TEST", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 640, 0); + SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, rendererFlags); + + // 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; + } + default: + { + break; + } + } + } + + // 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, width/2, height/2, &gravityVector); + + // Make it into a unit vector: + gravityMagnitude = normalizeXYVector(&gravityVector); + + // Calculate the gravity between the star and ship: + gravityAcceleration = (gravityMagnitude > 15) ? + 2 * (2500 / pow(gravityMagnitude, 2)): + 0.02 * (2500 / pow(gravityMagnitude, 2)); + + // Scale the vector: + multiplyXYVector(&gravityVector, gravityAcceleration); + + // Wrap the position if the ship goes off-screen: + if(positionVector.xComponent > width + 15) + { + positionVector.xComponent = 0; + velocityVector.xComponent *= 0.6; + } + if(positionVector.yComponent > height + 15) + { + positionVector.yComponent = 0; + velocityVector.yComponent *= 0.6; + } + if(positionVector.xComponent < -15) + { + positionVector.xComponent = width; + velocityVector.xComponent *= 0.6; + } + if(positionVector.yComponent < -15) + { + positionVector.yComponent = height; + velocityVector.yComponent *= 0.6; + } + + // Calculate the new current velocity: + addXYVectorDeltaScaled(&velocityVector, &gravityVector, deltaTime); + + // Calculate the new position: + addXYVectorDeltaScaled(&positionVector, &velocityVector, deltaTime); + + positionX = (long)positionVector.xComponent; + positionY = (long)positionVector.yComponent; + + // Set the colour to black: + SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); + + // Clear the screen, filling it with black: + SDL_RenderClear(renderer); + + // Set the colour to green: + SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255); + + // Draw a circle "ship" around the current position: + DrawCircle(renderer, positionX, positionY, 15); + + // Set the colour to yellow: + SDL_SetRenderDrawColor(renderer, 255, 255, 0, 255); + + // Draw a circle in the center as the star: + DrawCircle(renderer, width/2, height/2, 30); + + // Draw a line representing the velocity: + SDL_RenderDrawLine(renderer, positionX, positionY, + (long)(positionVector.xComponent + velocityVector.xComponent * 3), + (long)(positionVector.yComponent + velocityVector.yComponent * 3)); + + // Present the rendered graphics: + SDL_RenderPresent(renderer); + } + return 0; +} +// =========================================================================================== +// Local Variables: +// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-07.c -lm" +// End: