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Spacewar
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Clean-up to make it easier to continue developing.

This commit is contained in:
Barra Ó Catháin 2023-03-15 23:39:23 +00:00
parent 21f4786a99
commit dcbf5b8ae2
1 changed files with 78 additions and 46 deletions
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124
Spacewar.c
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@ -1,4 +1,4 @@
// SDL Experiment 06, Barra Ó Catháin.
// SDL Experiment 07, Barra Ó Catháin.
// ===================================
#include <SDL2/SDL.h>
#include <SDL2/SDL_timer.h>
@ -6,6 +6,48 @@
#include <stdbool.h>
#include <stdint.h>
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);
@ -49,12 +91,12 @@ int main(int argc, char ** argv)
SDL_Event event;
bool quit = false;
int width = 0, height = 0;
uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0;
uint32_t rendererFlags = SDL_RENDERER_ACCELERATED;
double posX = 0, posY = 0, deltaTime = 0;
double deltaTime = 0, gravityMagnitude = 0, gravityAcceleration = 0;
uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 0;
long positionX = 0, positionY = 0;
double velocityX = 20, velocityY = 0, gravityX = 0, gravityY = 0, gravityMagnitude = 0, gravityAcceleration = 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)
{
@ -94,62 +136,50 @@ int main(int argc, char ** argv)
// 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);
xyVectorBetweenPoints(positionVector.xComponent, positionVector.yComponent, width/2, height/2, &gravityVector);
// 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;
}
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(posX > width + 15)
if(positionVector.xComponent > width + 15)
{
posX = 0;
velocityX *= 0.6;
positionVector.xComponent = 0;
velocityVector.xComponent *= 0.6;
}
if(posY > height + 15)
if(positionVector.yComponent > height + 15)
{
posY = 0;
velocityY *= 0.6;
positionVector.yComponent = 0;
velocityVector.yComponent *= 0.6;
}
if(posX < -15)
if(positionVector.xComponent < -15)
{
posX = width;
velocityX *= 0.6;
positionVector.xComponent = width;
velocityVector.xComponent *= 0.6;
}
if(posY < -15)
if(positionVector.yComponent < -15)
{
posY = height;
velocityY *= 0.6;
positionVector.yComponent = height;
velocityVector.yComponent *= 0.6;
}
// Calculate the new current velocity:
velocityX += gravityX * (deltaTime * 0.001) * 60;
velocityY += gravityY * (deltaTime * 0.001) * 60;
addXYVectorDeltaScaled(&velocityVector, &gravityVector, deltaTime);
// Calculate the new position:
posX += velocityX * (deltaTime * 0.001) * 60;
posY += velocityY * (deltaTime * 0.001) * 60;
positionX = (long)posX;
positionY = (long)posY;
addXYVectorDeltaScaled(&positionVector, &velocityVector, deltaTime);
positionX = (long)positionVector.xComponent;
positionY = (long)positionVector.yComponent;
// Set the colour to black:
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
@ -170,7 +200,9 @@ int main(int argc, char ** argv)
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));
SDL_RenderDrawLine(renderer, positionX, positionY,
(long)(positionVector.xComponent + velocityVector.xComponent * 3),
(long)(positionVector.yComponent + velocityVector.yComponent * 3));
// Present the rendered graphics:
SDL_RenderPresent(renderer);
@ -179,5 +211,5 @@ int main(int argc, char ** argv)
}
// ===========================================================================================
// Local Variables:
// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-06.c -lm"
// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-07.c -lm"
// End: