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Added SDL2 Experiment 8 

A mouse-based gravity program where the mouse is now the star from the previous experiments.
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Barry Kane 2023-02-04 18:17:51 +00:00
parent 1fd254bc36
commit 96b221f804
1 changed files with 227 additions and 0 deletions
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SDL2-Bits-And-Pieces/SDL2-Experiment-08.c Normal file
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// SDL Experiment 08, Barra Ó Catháin.
// ===================================
#include <SDL2/SDL.h>
#include <SDL2/SDL_timer.h>
#include <math.h>
#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);
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;
long positionX = 0, positionY = 0;
int width = 0, height = 0, mouseX = 0, mouseY = 0;
uint32_t rendererFlags = SDL_RENDERER_ACCELERATED;
double deltaTime = 0, gravityMagnitude = 0, gravityAcceleration = 0;
uint64_t thisFrameTime = SDL_GetPerformanceCounter(), lastFrameTime = 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);
// Store the mouse pointer's current position in the window:
SDL_GetMouseState(&mouseX, &mouseY);
// Calculate the vector between the star and ship:
xyVectorBetweenPoints(positionVector.xComponent, positionVector.yComponent, mouseX, mouseY, &gravityVector);
// Make it into a unit vector:
gravityMagnitude = normalizeXYVector(&gravityVector);
// Calculate the gravity between the star and ship:
if(gravityMagnitude > 45)
{
gravityAcceleration = 2 * (2500 / pow(gravityMagnitude, 2));
}
else
{
gravityAcceleration = 0;
multiplyXYVector(&velocityVector, -0.98);
}
// 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, mouseX, mouseY, 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);
// Delay enough so that we run at 60 frames:
SDL_Delay(1000 / 144);
}
return 0;
}
// ===========================================================================================
// Local Variables:
// compile-command: "gcc `sdl2-config --libs --cflags` SDL2-Experiment-08.c -lm"
// End: