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Update shapes_double_pendulum.c

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Ray
2025-08-07 17:07:45 +02:00
parent d45b00b191
commit f02c7fca8a
1 changed files with 37 additions and 48 deletions
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85
examples/shapes/shapes_double_pendulum.c
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@@ -22,12 +22,6 @@
//----------------------------------------------------------------------------------
// Macro Helpers
//----------------------------------------------------------------------------------
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 450
#define CENTER_X SCREEN_WIDTH * 0.5
#define CENTER_Y SCREEN_HEIGHT * 0.5 - 100
// Constant for Simulation
#define SIMULATION_STEPS 30
#define G 9.81
@@ -45,32 +39,32 @@ int main(void)
{
// Initialization
//--------------------------------------------------------------------------------------
const int screenWidth = 800;
const int screenHeight = 450;
SetConfigFlags(FLAG_WINDOW_HIGHDPI);
InitWindow(SCREEN_WIDTH, SCREEN_HEIGHT, "raylib [shapes] example - Double Pendulum");
InitWindow(screenWidth, screenHeight, "raylib [shapes] example - double pendulum");
// Simulation Paramters
//--------------------------------------------------------------------------------------
float l1 = 15, m1 = 0.2, theta1 = DEG2RAD * 170, w1 = 0;
float l2 = 15, m2 = 0.1, theta2 = DEG2RAD * 0, w2 = 0;
float lengthScaler = 0.1;
float totalM = m1 + m2;
Vector2 previousPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2);
previousPosition.x += CENTER_X;
previousPosition.y += CENTER_Y;
previousPosition.x += (screenWidth/2);
previousPosition.y += (screenHeight/2 - 100);
// Scale length
float L1 = l1 * lengthScaler;
float L2 = l2 * lengthScaler;
// Draw Parameters
//--------------------------------------------------------------------------------------
// Draw parameters
int lineThick = 20, trailThick = 2;
float fateAlpha = 0.01;
// Create Framebuffer
//--------------------------------------------------------------------------------------
RenderTexture2D target = LoadRenderTexture(SCREEN_WIDTH, SCREEN_HEIGHT);
// Create framebuffer
RenderTexture2D target = LoadRenderTexture(screenWidth, screenHeight);
SetTextureFilter(target.texture, TEXTURE_FILTER_BILINEAR);
SetTargetFPS(60);
@@ -80,60 +74,56 @@ int main(void)
while (!WindowShouldClose()) // Detect window close button or ESC key
{
// Update
//----------------------------------------------------------------------------------
float dt = GetFrameTime();
float step = dt / SIMULATION_STEPS, step2 = step * step;
// Update Physics - larger steps = better approximation
//----------------------------------------------------------------------------------
for (int i = 0; i < SIMULATION_STEPS; ++i)
{
float delta = theta1 - theta2;
float sinD = sin(delta), cosD = cos(delta), cos2D = cos(2 * delta);
float sinD = sinf(delta), cosD = cosf(delta), cos2D = cosf(2*delta);
float ww1 = w1 * w1, ww2 = w2 * w2;
// Calculate a1
float a1 = (-G * (2 * m1 + m2) * sin(theta1)
- m2 * G * sin(theta1 - 2 * theta2)
- 2 * sinD * m2 * (ww2 * L2 + ww1 * L1 * cosD))
/ (L1 * (2 * m1 + m2 - m2 * cos2D));
float a1 = (-G*(2*m1 + m2)*sinf(theta1)
- m2*G*sinf(theta1 - 2*theta2)
- 2*sinD*m2*(ww2*L2 + ww1*L1*cosD))
/ (L1*(2*m1 + m2 - m2*cos2D));
// Calculate a2
float a2 = (2 * sinD * (ww1 * L1 * totalM
+ G * totalM * cos(theta1)
+ ww2 * L2 * m2 * cosD))
/ (L2 * (2 * m1 + m2 - m2 * cos2D));
float a2 = (2*sinD*(ww1*L1*totalM
+ G*totalM*cosf(theta1)
+ ww2*L2*m2*cosD))
/ (L2*(2*m1 + m2 - m2*cos2D));
// Update thetas
theta1 += w1 * step + 0.5 * a1 * step2;
theta2 += w2 * step + 0.5 * a2 * step2;
theta1 += w1*step + 0.5f*a1*step2;
theta2 += w2*step + 0.5f*a2*step2;
// Update omegas
w1 += a1 * step;
w2 += a2 * step;
w1 += a1*step;
w2 += a2*step;
}
//----------------------------------------------------------------------------------
// Calculate position
Vector2 currentPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2);
currentPosition.x += CENTER_X;
currentPosition.y += CENTER_Y;
currentPosition.x += screenWidth/2;
currentPosition.y += screenHeight/2 - 100;
// Draw to framebuffer
//----------------------------------------------------------------------------------
// Draw to render texture
BeginTextureMode(target);
// Draw a transparent rectangle - smaller alpha = longer trails
DrawRectangle(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, Fade(BLACK, fateAlpha));
DrawRectangle(0, 0, screenWidth, screenHeight, Fade(BLACK, fateAlpha));
// Draw trail
DrawCircleV(previousPosition, trailThick, RED);
DrawLineEx(previousPosition, currentPosition, trailThick * 2, RED);
EndTextureMode();
//----------------------------------------------------------------------------------
// Update previous position
previousPosition = currentPosition;
//----------------------------------------------------------------------------------
// Draw
//----------------------------------------------------------------------------------
@@ -141,17 +131,16 @@ int main(void)
ClearBackground(BLACK);
// Draw Trails Texture
DrawTextureRec(target.texture, (Rectangle){ 0, 0, target.texture.width, -target.texture.height },
(Vector2){ 0, 0 }, WHITE);
// Draw trails texture
DrawTextureRec(target.texture, (Rectangle){ 0, 0, target.texture.width, -target.texture.height }, (Vector2){ 0, 0 }, WHITE);
// Draw Double Pendulum
DrawRectanglePro((Rectangle){ CENTER_X, CENTER_Y, 10 * l1, lineThick },
(Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta1, RAYWHITE);
// Draw double pendulum
DrawRectanglePro((Rectangle){ screenWidth/2, screenHeight/2 - 100, 10 * l1, lineThick },
(Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta1, RAYWHITE);
Vector2 endpoint1 = CalculatePendulumEndPoint(l1, theta1);
DrawRectanglePro((Rectangle){ CENTER_X + endpoint1.x, CENTER_Y + endpoint1.y, 10 * l2, lineThick },
(Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta2, RAYWHITE);
DrawRectanglePro((Rectangle){ screenWidth/2 + endpoint1.x, screenHeight/2 - 100 + endpoint1.y, 10 * l2, lineThick },
(Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta2, RAYWHITE);
EndDrawing();
//----------------------------------------------------------------------------------