physics.h File Reference

#include "_math.h"
#include "body.h"
#include "body_list.h"
#include "collision.h"
#include "gapi.h"
#include "position.h"
#include "system.h"

Go to the source code of this file.

Functions
void	gm_collision_resolve (gmCollision *collision)
	Resolves a collision between two bodies by applying appropriate forces and corrections.
void	gm_system_update_body_dt (gmSystem *sys, gmBody *body, double dt)
	Updates a single physics body's position and velocity based on applied accelerations and damping.
void	gm_body_update_dt (gmBody *body, double dt)
	Updates a single physics body's position and velocity using a specified time step, without considering a global physics system.
void	gm_body_update (gmBody *body)
	Updates a single physics body's position and velocity using the engine's global delta time (gm_dt()), without considering a global physics system.
gmCollision *	gm_collision_detect (gmBody *, gmBody *)
	Detects a collision between two physics bodies.
void	gm_system_update_dt (gmSystem *sys, double unit, double dt)
	Updates a physics system over a given total time step, performing sub-steps for stable collision detection and resolution.
int	gm_system_get_collision (gmCollision *collision, gmSystem *sys, gmBody *a, gmBody *b)
	Gets the collision information for two specific bodies in a system.
double	gm_collision_penetration_normals (gmBody *a, gmBody *b, double *normal_x, double *normal_y)
	Calculates the penetration depth and optionally the normal vector for a collision between two bodies.
double	gm_collision_penetration (gmBody *a, gmBody *b)
	Calculates the penetration depth for a collision between two bodies.

Variables
double	gm_system_frame_time = 0.001
	Default time step for physics system frame updates.

Function Documentation

gm_body_update()

void gm_body_update

(

gmBody *

body

)

Updates a single physics body's position and velocity using the engine's global delta time (gm_dt()), without considering a global physics system.

Parameters

body	Pointer to the body to update.

gm_body_update_dt()

void gm_body_update_dt	(	gmBody *	body,
		double	dt )

Updates a single physics body's position and velocity using a specified time step, without considering a global physics system.

Parameters

body	Pointer to the body to update.
dt	The time step for the update.

gm_collision_detect()

gmCollision * gm_collision_detect	(	gmBody *	a,
		gmBody *	b )

Detects a collision between two physics bodies.

Parameters

a	Pointer to the first body.
b	Pointer to the second body.

Returns

A pointer to a gmCollision structure if a collision is detected, otherwise NULL. The returned gmCollision must be freed by the caller if it's not managed by a gmSystem.

Detects a collision between two physics bodies.

This function dispatches to specific collision tests (e.g., AABB vs AABB, Circle vs Circle, Circle vs AABB) based on the collider_type of the input bodies.

Parameters

a	Pointer to the first body.
b	Pointer to the second body.

Returns

A dynamically allocated gmCollision structure if a collision occurs, otherwise NULL. The caller is responsible for freeing the returned gmCollision object if it's not managed by a gmSystem.

gm_collision_penetration()

double gm_collision_penetration	(	gmBody *	a,
		gmBody *	b )

Calculates the penetration depth for a collision between two bodies.

This function is a simplified version of gm_collision_penetration_normals that only returns the depth and does not calculate the normal vector.

Parameters

a	Pointer to the first body.
b	Pointer to the second body.

Returns

The penetration depth between the bodies. A positive value indicates overlap.

gm_collision_penetration_normals()

double gm_collision_penetration_normals	(	gmBody *	a,
		gmBody *	b,
		double *	normal_x,
		double *	normal_y )

Calculates the penetration depth and optionally the normal vector for a collision between two bodies.

This function handles collision between various collider types (Circle-Circle, Rect-Rect, Circle-Rect). It determines how much the bodies overlap and the direction of the separation.

Parameters

a	Pointer to the first body.
b	Pointer to the second body.
normal_x	Pointer to store the x component of the collision normal (can be NULL if not needed). The normal points from body a to body b.
normal_y	Pointer to store the y component of the collision normal (can be NULL if not needed). The normal points from body a to body b.

Returns

The penetration depth between the bodies. A positive value indicates overlap.

gm_collision_resolve()

void gm_collision_resolve

(

gmCollision *

coll

)

Resolves a collision between two bodies by applying appropriate forces and corrections.

Resolves a collision by adjusting positions and velocities of colliding bodies.

Parameters

collision	Pointer to the collision to resolve.
coll	Pointer to the collision to resolve.

gm_system_get_collision()

int gm_system_get_collision	(	gmCollision *	collision,
		gmSystem *	sys,
		gmBody *	a,
		gmBody *	b )

Gets the collision information for two specific bodies in a system.

This function searches the system's active collisions to find one involving the two specified bodies.

Parameters

collision	Pointer to a gmCollision struct where the found collision data will be copied. Can be NULL if only checking for existence.
sys	Pointer to the system to search in.
a	Pointer to the first body.
b	Pointer to the second body.

Returns

1 if a collision involving a and b is found, 0 otherwise.

gm_system_update_body_dt()

void gm_system_update_body_dt	(	gmSystem *	sys,
		gmBody *	body,
		double	dt )

Updates a single physics body's position and velocity based on applied accelerations and damping.

This function integrates the body's motion over a given time step. It accounts for the body's own acceleration and any system-wide acceleration and damping.

Parameters

sys	Pointer to the physics system the body belongs to (can be NULL if no system-wide effects are desired).
body	Pointer to the body to update.
dt	The time step (delta time) for the update.

gm_system_update_dt()

void gm_system_update_dt	(	gmSystem *	sys,
		double	unit,
		double	dt )

Updates a physics system over a given total time step, performing sub-steps for stable collision detection and resolution.

This is the main update function for a physics system. It integrates the motion of all bodies, detects new collisions, resolves them, and manages the lifecycle of collision objects.

Parameters

sys	Pointer to the system to update.
unit	The duration of each sub-step for physics integration.
dt	The total time duration to simulate in this update.

Variable Documentation

gm_system_frame_time

double gm_system_frame_time = 0.001

Default time step for physics system frame updates.

This value determines the granularity of physics calculations per frame. A smaller value leads to more accurate (and potentially slower) simulations.