ref: 08d0015032b413d93ea4e7aa18c26c94bf69f29d
dir: /SDL_Examples/include/chadphys.h/
#ifndef CHAD_PHYS_H
#define CHAD_PHYS_H
#ifdef CHAD_PHYS_IMPL
#define CHAD_MATH_IMPL
#endif
#include "3dMath.h"
typedef struct {
aabb shape; //c.d[3] is sphere radius.
//if it's zero or less, it's not a sphere, it's a box
f_ mass; //0 means kinematic, or static. Defaults to zero.
f_ bounciness; //default 0, put portion of displacement into velocity.
f_ airfriction; //default 1, multiplied by velocity every time timestep.
f_ friction; //default 0.1
vec3 r; //Rotation, Used for rendering only
vec3 v; //velocity
vec3 a; //Body specific acceleration, combined with gravity
void* d; //User defined pointer.
} phys_body;
typedef struct{
phys_body* abodies; //mass non-zero
phys_body* sbodies; //mass zero
uint nabodies; //number of abodies
uint nsbodies; //number of sbodies
vec3 g; //gravity
f_ ms; //max speed
} phys_world;
void stepPhysWorld(phys_world* world);
void resolveBodies(phys_body* a, phys_body* b);
void initPhysWorld(phys_world* world); //inits to NULL
void initPhysBody(phys_body* body); //inits to defaults specified above.
#ifdef CHAD_PHYS_IMPL
//TODO: implement functions
void initPhysBody(phys_body* body){
body->shape = (aabb){
.c=(vec4){.d[0] = 0,.d[1] = 0,.d[2] = 0,.d[3] = 0},
.e=(vec3){.d[0] = 0,.d[1] = 0,.d[2] = 0}
};
body->mass = 0;
body->bounciness = 0;
body->friction = 0.1;
body->airfriction = 1.0;
body->a = (vec3){.d[0] = 0,.d[1] = 0,.d[2] = 0};
body->r = (vec3){.d[0] = 0,.d[1] = 0,.d[2] = 0};
body->d = NULL;
}
//Check for and, if necessary, resolve colliding bodies.
void resolveBodies(phys_body* a, phys_body* b){
if(a->mass <= 0 && b->mass <= 0) return; //Perform a preliminary check. Do we even have to do anything?
//Check if the two bodies are colliding.
vec4 penvec = (vec4){
.d[0]=0,
.d[1]=0,
.d[2]=0,
.d[3]=0
};
if(a->shape.c.d[3] > 0 && b->shape.c.d[3] > 0) //Both Spheres!
{
penvec = spherevsphere(a->shape.c, b->shape.c);
} else if(a->shape.c.d[3] <= 0 && b->shape.c.d[3] <= 0) //Both boxes!
{
penvec = boxvbox(a->shape,b->shape);
} else if (a->shape.c.d[3] > 0 && b->shape.c.d[3] <= 0) //a is a sphere, b is a box
{
penvec = spherevaabb(a->shape.c,b->shape);
} else if (a->shape.c.d[3] <= 0 && b->shape.c.d[3] > 0){ //a is a box, b is a sphere
penvec = spherevaabb(b->shape.c,a->shape);
penvec.d[0] *= -1;
penvec.d[1] *= -1;
penvec.d[2] *= -1;
} else {
puts("\nInvalid configuration. Error.\n");
}
if(penvec.d[3] <= 0) return; //No penetration detected, or invalid configuration.
//We now have the penetration vector. There is a penetration.
//determine how much each should be displaced by.
//The penvec points INTO A and is of length penvec.d[3]
float bdisplacefactor = a->mass / (a->mass + b->mass), adisplacefactor = b->mass / (a->mass + b->mass);
if(!(a->mass > 0)) {adisplacefactor = 0; bdisplacefactor = 1;}
if(!(b->mass > 0)) {bdisplacefactor = 0; adisplacefactor = 1;}
vec3 avel = a->v;
vec3 bvel = b->v;
vec3 arelvel = subv3(a->v, b->v);
vec3 brelvel = subv3(b->v, a->v);
if(a->mass > 0){
vec4 displacea = scalev4(-adisplacefactor, penvec); //Note: SSE will accelerate a 4-lane multiply better than 3.
a->shape.c.d[0] += displacea.d[0];
a->shape.c.d[1] += displacea.d[1];
a->shape.c.d[2] += displacea.d[2];
a->v = addv3(scalev3(1.0-a->friction, arelvel),bvel); //Apply friction!
a->v = addv3(a->v, scalev3( a->bounciness, downv4(displacea) ) );
}
if(b->mass > 0){
vec4 displaceb = scalev4(bdisplacefactor, penvec); //The vector returned by collision functions points INTO B!
b->shape.c.d[0] += displaceb.d[0];
b->shape.c.d[1] += displaceb.d[1];
b->shape.c.d[2] += displaceb.d[2];
b->v = addv3(scalev3(1.0 - b->friction, brelvel),avel);
b->v = addv3(b->v, scalev3( b->bounciness, downv4(displaceb) ) );
}
}
#endif
#endif