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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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63
examples/shapes/shapes_double_pendulum.c
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@@ -22,12 +22,6 @@
//---------------------------------------------------------------------------------- //----------------------------------------------------------------------------------
// Macro Helpers // 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 // Constant for Simulation
#define SIMULATION_STEPS 30 #define SIMULATION_STEPS 30
#define G 9.81 #define G 9.81
@@ -45,32 +39,32 @@ int main(void)
{ {
// Initialization // Initialization
//-------------------------------------------------------------------------------------- //--------------------------------------------------------------------------------------
const int screenWidth = 800;
const int screenHeight = 450;
SetConfigFlags(FLAG_WINDOW_HIGHDPI); SetConfigFlags(FLAG_WINDOW_HIGHDPI);
InitWindow(SCREEN_WIDTH, SCREEN_HEIGHT, "raylib [shapes] example - Double Pendulum"); InitWindow(screenWidth, screenHeight, "raylib [shapes] example - double pendulum");
// Simulation Paramters // Simulation Paramters
//--------------------------------------------------------------------------------------
float l1 = 15, m1 = 0.2, theta1 = DEG2RAD * 170, w1 = 0; float l1 = 15, m1 = 0.2, theta1 = DEG2RAD * 170, w1 = 0;
float l2 = 15, m2 = 0.1, theta2 = DEG2RAD * 0, w2 = 0; float l2 = 15, m2 = 0.1, theta2 = DEG2RAD * 0, w2 = 0;
float lengthScaler = 0.1; float lengthScaler = 0.1;
float totalM = m1 + m2; float totalM = m1 + m2;
Vector2 previousPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2); Vector2 previousPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2);
previousPosition.x += CENTER_X; previousPosition.x += (screenWidth/2);
previousPosition.y += CENTER_Y; previousPosition.y += (screenHeight/2 - 100);
// Scale length // Scale length
float L1 = l1 * lengthScaler; float L1 = l1 * lengthScaler;
float L2 = l2 * lengthScaler; float L2 = l2 * lengthScaler;
// Draw Parameters // Draw parameters
//--------------------------------------------------------------------------------------
int lineThick = 20, trailThick = 2; int lineThick = 20, trailThick = 2;
float fateAlpha = 0.01; float fateAlpha = 0.01;
// Create Framebuffer // Create framebuffer
//-------------------------------------------------------------------------------------- RenderTexture2D target = LoadRenderTexture(screenWidth, screenHeight);
RenderTexture2D target = LoadRenderTexture(SCREEN_WIDTH, SCREEN_HEIGHT);
SetTextureFilter(target.texture, TEXTURE_FILTER_BILINEAR); SetTextureFilter(target.texture, TEXTURE_FILTER_BILINEAR);
SetTargetFPS(60); SetTargetFPS(60);
@@ -80,60 +74,56 @@ int main(void)
while (!WindowShouldClose()) // Detect window close button or ESC key while (!WindowShouldClose()) // Detect window close button or ESC key
{ {
// Update // Update
//----------------------------------------------------------------------------------
float dt = GetFrameTime(); float dt = GetFrameTime();
float step = dt / SIMULATION_STEPS, step2 = step * step; float step = dt / SIMULATION_STEPS, step2 = step * step;
// Update Physics - larger steps = better approximation // Update Physics - larger steps = better approximation
//----------------------------------------------------------------------------------
for (int i = 0; i < SIMULATION_STEPS; ++i) for (int i = 0; i < SIMULATION_STEPS; ++i)
{ {
float delta = theta1 - theta2; 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; float ww1 = w1 * w1, ww2 = w2 * w2;
// Calculate a1 // Calculate a1
float a1 = (-G * (2 * m1 + m2) * sin(theta1) float a1 = (-G*(2*m1 + m2)*sinf(theta1)
- m2 * G * sin(theta1 - 2 * theta2) - m2*G*sinf(theta1 - 2*theta2)
- 2*sinD*m2*(ww2*L2 + ww1*L1*cosD)) - 2*sinD*m2*(ww2*L2 + ww1*L1*cosD))
/ (L1*(2*m1 + m2 - m2*cos2D)); / (L1*(2*m1 + m2 - m2*cos2D));
// Calculate a2 // Calculate a2
float a2 = (2*sinD*(ww1*L1*totalM float a2 = (2*sinD*(ww1*L1*totalM
+ G * totalM * cos(theta1) + G*totalM*cosf(theta1)
+ ww2*L2*m2*cosD)) + ww2*L2*m2*cosD))
/ (L2*(2*m1 + m2 - m2*cos2D)); / (L2*(2*m1 + m2 - m2*cos2D));
// Update thetas // Update thetas
theta1 += w1 * step + 0.5 * a1 * step2; theta1 += w1*step + 0.5f*a1*step2;
theta2 += w2 * step + 0.5 * a2 * step2; theta2 += w2*step + 0.5f*a2*step2;
// Update omegas // Update omegas
w1 += a1*step; w1 += a1*step;
w2 += a2*step; w2 += a2*step;
} }
//----------------------------------------------------------------------------------
// Calculate position // Calculate position
Vector2 currentPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2); Vector2 currentPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2);
currentPosition.x += CENTER_X; currentPosition.x += screenWidth/2;
currentPosition.y += CENTER_Y; currentPosition.y += screenHeight/2 - 100;
// Draw to framebuffer // Draw to render texture
//----------------------------------------------------------------------------------
BeginTextureMode(target); BeginTextureMode(target);
// Draw a transparent rectangle - smaller alpha = longer trails // 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 // Draw trail
DrawCircleV(previousPosition, trailThick, RED); DrawCircleV(previousPosition, trailThick, RED);
DrawLineEx(previousPosition, currentPosition, trailThick * 2, RED); DrawLineEx(previousPosition, currentPosition, trailThick * 2, RED);
EndTextureMode(); EndTextureMode();
//----------------------------------------------------------------------------------
// Update previous position // Update previous position
previousPosition = currentPosition; previousPosition = currentPosition;
//----------------------------------------------------------------------------------
// Draw // Draw
//---------------------------------------------------------------------------------- //----------------------------------------------------------------------------------
@@ -141,16 +131,15 @@ int main(void)
ClearBackground(BLACK); ClearBackground(BLACK);
// Draw Trails Texture // Draw trails texture
DrawTextureRec(target.texture, (Rectangle){ 0, 0, target.texture.width, -target.texture.height }, DrawTextureRec(target.texture, (Rectangle){ 0, 0, target.texture.width, -target.texture.height }, (Vector2){ 0, 0 }, WHITE);
(Vector2){ 0, 0 }, WHITE);
// Draw Double Pendulum // Draw double pendulum
DrawRectanglePro((Rectangle){ CENTER_X, CENTER_Y, 10 * l1, lineThick }, DrawRectanglePro((Rectangle){ screenWidth/2, screenHeight/2 - 100, 10 * l1, lineThick },
(Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta1, RAYWHITE); (Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta1, RAYWHITE);
Vector2 endpoint1 = CalculatePendulumEndPoint(l1, theta1); Vector2 endpoint1 = CalculatePendulumEndPoint(l1, theta1);
DrawRectanglePro((Rectangle){ CENTER_X + endpoint1.x, CENTER_Y + endpoint1.y, 10 * l2, lineThick }, DrawRectanglePro((Rectangle){ screenWidth/2 + endpoint1.x, screenHeight/2 - 100 + endpoint1.y, 10 * l2, lineThick },
(Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta2, RAYWHITE); (Vector2){0, lineThick * 0.5}, 90 - RAD2DEG * theta2, RAYWHITE);
EndDrawing(); EndDrawing();