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Modified the simulation to use delta-time scaling.

This commit is contained in:
Barra Ó Catháin 2023-03-15 23:31:52 +00:00
parent 6df411a1a2
commit 21f4786a99
1 changed files with 15 additions and 13 deletions
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28
SDL2-Experiment-05.c → Spacewar.c
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@ -1,4 +1,4 @@
// SDL Experiment 05, Barra Ó Catháin. // SDL Experiment 06, Barra Ó Catháin.
// =================================== // ===================================
#include <SDL2/SDL.h> #include <SDL2/SDL.h>
#include <SDL2/SDL_timer.h> #include <SDL2/SDL_timer.h>
@ -49,8 +49,9 @@ int main(int argc, char ** argv)
SDL_Event event; SDL_Event event;
bool quit = false; bool quit = false;
int width = 0, height = 0; int width = 0, height = 0;
uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0;
uint32_t rendererFlags = SDL_RENDERER_ACCELERATED; uint32_t rendererFlags = SDL_RENDERER_ACCELERATED;
double posX = 0, posY = 0; double posX = 0, posY = 0, deltaTime = 0;
long positionX = 0, positionY = 0; long positionX = 0, positionY = 0;
double velocityX = 20, velocityY = 0, gravityX = 0, gravityY = 0, gravityMagnitude = 0, gravityAcceleration = 0; double velocityX = 20, velocityY = 0, gravityX = 0, gravityY = 0, gravityMagnitude = 0, gravityAcceleration = 0;
@ -59,7 +60,7 @@ int main(int argc, char ** argv)
{ {
printf("SDL Initialization Error: %s\n", SDL_GetError()); printf("SDL Initialization Error: %s\n", SDL_GetError());
} }
// Create an SDL window and rendering context in that window: // 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_Window * window = SDL_CreateWindow("SDL_TEST", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 640, 0);
SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, rendererFlags); SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, rendererFlags);
@ -69,6 +70,10 @@ int main(int argc, char ** argv)
while (!quit) while (!quit)
{ {
lastFrameTime = thisFrameTime;
thisFrameTime = SDL_GetPerformanceCounter();
deltaTime = (double)(((thisFrameTime - lastFrameTime) * 1000) / (double)SDL_GetPerformanceFrequency());
// Check if the user wants to quit: // Check if the user wants to quit:
while (SDL_PollEvent(&event)) while (SDL_PollEvent(&event))
{ {
@ -100,7 +105,7 @@ int main(int argc, char ** argv)
gravityY /= gravityMagnitude; gravityY /= gravityMagnitude;
// Calculate the gravity between them and scale the vector: // Calculate the gravity between them and scale the vector:
if(gravityMagnitude > 15) if(gravityMagnitude > 15)
{ {
gravityAcceleration = 2 * (2500 / pow(gravityMagnitude, 2)); gravityAcceleration = 2 * (2500 / pow(gravityMagnitude, 2));
gravityX *= gravityAcceleration; gravityX *= gravityAcceleration;
@ -136,12 +141,12 @@ int main(int argc, char ** argv)
} }
// Calculate the new current velocity: // Calculate the new current velocity:
velocityX += gravityX; velocityX += gravityX * (deltaTime * 0.001) * 60;
velocityY += gravityY; velocityY += gravityY * (deltaTime * 0.001) * 60;
// Calculate the new position: // Calculate the new position:
posX += velocityX; posX += velocityX * (deltaTime * 0.001) * 60;
posY += velocityY; posY += velocityY * (deltaTime * 0.001) * 60;
positionX = (long)posX; positionX = (long)posX;
positionY = (long)posY; positionY = (long)posY;
@ -165,17 +170,14 @@ int main(int argc, char ** argv)
DrawCircle(renderer, width/2, height/2, 30); DrawCircle(renderer, width/2, height/2, 30);
// Draw a line representing the velocity: // Draw a line representing the velocity:
SDL_RenderDrawLine(renderer, positionX, positionY, (long)((posX + velocityX * 3)), (long)((posY + velocityY * 3))); SDL_RenderDrawLine(renderer, positionX, positionY, (long)(posX + velocityX * 3), (long)(posY + velocityY * 3));
// Present the rendered graphics: // Present the rendered graphics:
SDL_RenderPresent(renderer); SDL_RenderPresent(renderer);
// Delay enough so that we run at 60 frames:
SDL_Delay(1000 / 60);
} }
return 0; return 0;
} }
// =========================================================================================== // ===========================================================================================
// Local Variables: // Local Variables:
// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-05.c -lm" // compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-06.c -lm"
// End: // End: