133 lines
3.1 KiB
C
133 lines
3.1 KiB
C
#include <math.h>
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// better hope you were paying attention in physics class for this one
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#include "physics.h"
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#include "world.h"
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#include "config.h"
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// Main physics update loop for all entities
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void UpdateEntities(float dt, int screenWidth)
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{
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// Iterate through all possible entities
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for (int i = 0; i < MAX_ENTITIES; i++)
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{
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Entity *e = &entities[i];
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// Skip inactive entities
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if (!e->active)
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continue;
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// Check if entity is currently touching the ground
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// YOU'RE GROUNDED!!! lol
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bool onGround = IsGrounded(e);
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// Apply gravity force if enabled for this entity
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if (e->affectedByGravity)
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{
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ApplyForce(
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e,
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(Vector2){0, e->mass * g}
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);
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}
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// Compute acceleration from accumulated forces (F = ma)
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e->acceleration.x =
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e->force.x / e->mass;
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e->acceleration.y =
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e->force.y / e->mass;
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// Integrate velocity from acceleration
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e->velocity.x +=
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e->acceleration.x * dt;
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e->velocity.y +=
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e->acceleration.y * dt;
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// Apply air drag to slow movement over time
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e->velocity.x *= AIR_DRAG;
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e->velocity.y *= AIR_DRAG;
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// Apply ground friction when on the ground
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if (onGround)
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{
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if (e->velocity.x > 0)
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{
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e->velocity.x -=
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GROUND_FRICTION * dt;
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if (e->velocity.x < 0)
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e->velocity.x = 0;
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}
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else if (e->velocity.x < 0)
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{
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e->velocity.x +=
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GROUND_FRICTION * dt;
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if (e->velocity.x > 0)
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e->velocity.x = 0;
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}
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}
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// Clamp player horizontal speed
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if (e->isPlayer)
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{
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if (e->velocity.x > MAX_PLAYER_SPEED)
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e->velocity.x = MAX_PLAYER_SPEED;
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if (e->velocity.x < -MAX_PLAYER_SPEED)
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e->velocity.x = -MAX_PLAYER_SPEED;
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}
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// Integrate position from velocity
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e->position.x +=
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e->velocity.x * dt;
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e->position.y +=
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e->velocity.y * dt;
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// Reset forces after integration step
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e->force = (Vector2){0, 0};
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// Ground collision
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if (e->position.y +
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e->size * 0.5f >=
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ground_y)
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{
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e->position.y =
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ground_y -
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e->size * 0.5f;
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e->velocity.y *=
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-BOUNCE;
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// Stop tiny bounces... or at least, attempt to.
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if (fabsf(e->velocity.y) < 15.0f)
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{
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e->velocity.y = 0;
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}
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}
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// Left wall collision
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if (e->position.x -
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e->size * 0.5f < 0)
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{
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e->position.x =
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e->size * 0.5f;
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e->velocity.x *= -0.6f;
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}
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// Right wall collision
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if (e->position.x +
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e->size * 0.5f >
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screenWidth)
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{
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e->position.x =
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screenWidth -
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e->size * 0.5f;
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e->velocity.x *= -0.6f;
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}
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}
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}
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