diff --git a/SDL2-Experiment-04.c b/SDL2-Experiment-05.c similarity index 54% rename from SDL2-Experiment-04.c rename to SDL2-Experiment-05.c index 23e165c..01904b1 100644 --- a/SDL2-Experiment-04.c +++ b/SDL2-Experiment-05.c @@ -1,7 +1,8 @@ -// SDL Experiment 04, Barra Ó Catháin. +// SDL Experiment 05, Barra Ó Catháin. // =================================== #include #include +#include #include #include @@ -43,28 +44,22 @@ void DrawCircle(SDL_Renderer * renderer, int32_t centreX, int32_t centreY, int32 } } -// Get the largest radius for a circle that can fit in the width and height of a rectangle: -static inline int getRadius(int width, int height) -{ - return (width/2 < height/2) ? width/2 : height/2; -} - - int main(int argc, char ** argv) { SDL_Event event; bool quit = false; int width = 0, height = 0; uint32_t rendererFlags = SDL_RENDERER_ACCELERATED; - long positionX = 320, positionY = 320, velocityX = 0, velocityY = 0; - bool accelLeft = false, accelRight = false, accelUp = false, accelDown = false; + double posX = 0, posY = 0; + long positionX = 0, positionY = 0; + double velocityX = 20, velocityY = 0, gravityX = 0, gravityY = 0, gravityMagnitude = 0, gravityAcceleration = 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); @@ -84,70 +79,6 @@ int main(int argc, char ** argv) quit = true; break; } - // Begin accelerating in the direction that is pressed: - case SDL_KEYDOWN: - { - switch (event.key.keysym.sym) - { - case SDLK_LEFT: - { - accelLeft = true; - break; - } - case SDLK_RIGHT: - { - accelRight = true; - break; - } - case SDLK_UP: - { - accelUp = true; - break; - } - case SDLK_DOWN: - { - accelDown = true; - break; - } - default: - { - break; - } - } - break; - } - // Stop accelerating in the direction that is released: - case SDL_KEYUP: - { - switch (event.key.keysym.sym) - { - case SDLK_LEFT: - { - accelLeft = false; - break; - } - case SDLK_RIGHT: - { - accelRight = false; - break; - } - case SDLK_UP: - { - accelUp = false; - break; - } - case SDLK_DOWN: - { - accelDown = false; - break; - } - default: - { - break; - } - } - break; - } default: { break; @@ -155,106 +86,96 @@ int main(int argc, char ** argv) } } - // Accelerate: - if(accelLeft) - { - velocityX -= 2; - } - - if(accelRight) - { - velocityX += 2; - } - - if(accelUp) - { - velocityY -= 2; - } - - if(accelDown) - { - velocityY += 2; - } - - // Limit velocity: - if(velocityX > 10) - { - velocityX = 10; - } - - if(velocityX < -10) - { - velocityX = -10; - } - - - // Deccelerate: - if(velocityX != 0) - { - velocityX = (velocityX < 0) ? velocityX + 1 : velocityX - 1; - } - - if(positionY < 640) - { - velocityY += 1; - } - if(positionY >= 640 && velocityY !=0 && !accelUp) - { - velocityY *= -1; - velocityY += 1; - } - - - // Move the position: - if(velocityX != 0) - { - positionX += velocityX; - if(positionX < 0) - { - positionX = 640; - } - if(positionX > 640) - { - positionX = 0; - } - } - if(velocityY != 0) - { - positionY += velocityY; - if(positionY < 0) - { - positionY = 0; - } - if(positionY > 640) - { - positionY = 640; - } - } - - // Store the window's current width and height: + // Store the window's current width and height: SDL_GetWindowSize(window, &width, &height); + // Calculate the gravity vector: + // Calculate the vector between the star and ship: + gravityX = (width/2 - posX); + gravityY = (height/2 - posY); + + // Make it into a unit vector: + gravityMagnitude = sqrt(pow(gravityX, 2) + pow(gravityY, 2)); + gravityX /= gravityMagnitude; + gravityY /= gravityMagnitude; + + // Calculate the gravity between them and scale the vector: + if(gravityMagnitude > 15) + { + gravityAcceleration = 2 * (2500 / pow(gravityMagnitude, 2)); + gravityX *= gravityAcceleration; + gravityY *= gravityAcceleration; + } + else + { + gravityAcceleration = 0.02 * (2500 / pow(gravityMagnitude, 2)); + gravityX *= gravityAcceleration; + gravityY *= gravityAcceleration; + } + + // Wrap the position if the ship goes off-screen: + if(posX > width + 15) + { + posX = 0; + velocityX *= 0.6; + } + if(posY > height + 15) + { + posY = 0; + velocityY *= 0.6; + } + if(posX < -15) + { + posX = width; + velocityX *= 0.6; + } + if(posY < -15) + { + posY = height; + velocityY *= 0.6; + } + + // Calculate the new current velocity: + velocityX += gravityX; + velocityY += gravityY; + + // Calculate the new position: + posX += velocityX; + posY += velocityY; + + positionX = (long)posX; + positionY = (long)posY; + // 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 around the position pointer: - DrawCircle(renderer, positionX, positionY, 15); + // 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)((posX + velocityX * 3)), (long)((posY + velocityY * 3))); + // Present the rendered graphics: SDL_RenderPresent(renderer); - // Delay enough so that we run at 144 frames: + // Delay enough so that we run at 60 frames: SDL_Delay(1000 / 60); } return 0; } // =========================================================================================== // Local Variables: -// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-04.c -lm" +// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-05.c -lm" // End: