ref: 9269b2aeddb72669cabd1a84a267b105cec5823d
dir: /include-demo/chadphys.h/
#ifndef CHAD_PHYS_H
#define CHAD_PHYS_H
#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
mat4 localt; //Local Transform.
vec3 v; //velocity
vec3 a; //Body specific acceleration, combined with gravity
void* d; //User defined pointer.
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
} phys_body;
typedef struct{
vec3 g; //gravity
phys_body* bodies;
f_ ms; //max speed
uint nbodies; //number of bodies
} phys_world;
typedef struct{
phys_body** data;
uint capacity;
} phys_cell;
typedef struct{
phys_cell* data;
f_ celldim;
uint xcells;
uint ycells;
uint zcells;
vec3 offset;
} phys_spatialhash;
static inline phys_spatialhash spatialhash_init(uint x, uint y, uint z, f_ celldim, vec3 offset){
phys_spatialhash ret = {0};
ret.xcells = x;
ret.ycells = y;
ret.zcells = z;
ret.celldim = celldim;
ret.offset = offset;
ret.data = calloc(1,sizeof(phys_cell) * x * y * z);
return ret;
}
static inline void destroy_spatialhash(phys_spatialhash* p){
if(p->data) free(p->data);
p->data = NULL;
}
static inline uint phys_cell_insert(phys_cell* c, phys_body* b){ //1 = error.
uint inserted = 0;
while(!inserted){
for(uint b_ = 0; b_ < c->capacity; b_++)
if(c->data[b_]==NULL)
{
c->data[b_] = b;
inserted = 1;
return 0;
}
phys_body** old = c->data;
c->data = calloc(1,((c->capacity)<<1) * sizeof(phys_body*));
if(c->data == NULL) { //The malloc failed! Wowza!
if(old)//In case we had something there...
free(old);
return 1;
}
memcpy(c->data, old, c->capacity);
c->capacity <<= 1;
free(old);
}
return 1; //Unreachable.
}
//update the placement of this body b in the spatial hash.
static inline void spatialhash_clear(phys_spatialhash* h){
#pragma omp parallel for collapse(4)
for(uint i = 0; i < h->xcells; i++)
for(uint j = 0; j < h->ycells; j++)
for(uint k = 0; k < h->zcells; k++)
for(uint b_cell = 0; b_cell < h->data[i+ j*h->xcells + k*h->xcells*h->ycells].capacity; b_cell++)
h->data[i+ j*h->xcells + k*h->xcells*h->ycells].data[b_cell] = NULL;
}
static inline uint spatialhash_update(phys_spatialhash* h, phys_body* b){
//Assumes that the spatial hash was cleared this frame- no duplicates.
vec3 b1c = downv4(b->shape.c);
f_ rad = 0;
if(b->shape.c.d[3] == 0){
vec3 b1max = addv3(b1c,b->shape.e);
rad = MAX(MAX(b1max.d[0],b1max.d[1]),b1max.d[2]);
} else {
rad = b->shape.c.d[3];
}
rad /= h->celldim;
b1c = addv3(h->offset, b1c);
b1c = scalev3(1.0/h->celldim, b1c);
ivec3 beg, end;
#pragma omp simd
for(int i = 0; i < 3; i++){
beg.d[i] = b1c.d[i] - rad;
end.d[i] = b1c.d[i] + rad;
}
//error checking.
for(int i = 0; i < 3; i++)
if(beg.d[i] < 0 || end.d[i] < 0) return 1;
if( end.d[0] > h->xcells ||
end.d[1] > h->ycells ||
end.d[2] > h->zcells)
return 1;
if( beg.d[0] > h->xcells ||
beg.d[1] > h->ycells ||
beg.d[2] > h->zcells)
return 1;
#pragma omp parallel for collapse(3)
for(uint i = beg.d[0]; i < h->xcells && i<=end.d[0]; i++)
for(uint j = beg.d[1]; j < h->ycells && j<=end.d[1]; j++)
for(uint k = beg.d[2]; k < h->zcells && k<=end.d[2]; k++){
phys_cell_insert(h->data+i+ j*h->xcells + k*h->xcells*h->ycells, b);
}
return 0;
}
static inline 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 = 0.99; //The amount of coplanar velocity preserved in collisions.
body->airfriction = 1.0;
body->a = (vec3){.d[0] = 0,.d[1] = 0,.d[2] = 0};
body->localt = identitymat4();
body->d = NULL;
}
static inline mat4 getPhysBodyRenderTransform(phys_body* body){
return multm4(
translate(downv4(body->shape.c)),
body->localt
);
}
//Check for and, if necessary, resolve colliding bodies.
static inline 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?
vec4 penvec = (vec4){
.d[0]=0,
.d[1]=0,
.d[2]=0,
.d[3]=0
};
//Check if the two bodies are colliding.
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 {
#ifdef CHADPHYS_DEBUG
puts("\nInvalid configuration. Error.\n");
#endif
}
if(penvec.d[3] <= 0) return; //No penetration detected, or invalid configuration.
vec3 penvecnormalized = scalev3(1.0/penvec.d[3], downv4(penvec)); //the penetration vector points into B...
float friction = a->friction * b->friction;
//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);
vec3 comvel;
if(!(a->mass > 0)) {
adisplacefactor = 0; bdisplacefactor = 1;comvel = (vec3){{0,0,0}};
}else if(!(b->mass > 0)) {
bdisplacefactor = 0; adisplacefactor = 1;comvel = (vec3){{0,0,0}};
}else{
comvel = addv3( scalev3(bdisplacefactor, a->v), scalev3(adisplacefactor, b->v));
}
if(a->mass > 0){
vec4 displacea = scalev4(-adisplacefactor, penvec);
vec3 a_relvel = subv3(a->v, comvel);
vec3 a_planarvel = subv3(a_relvel,
scalev3(
dotv3(a_relvel, penvecnormalized),
penvecnormalized
)
);
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( comvel, scalev3(1-friction, a_planarvel) ); //The center of mass velocity, plus a portion of coplanar velocity.
a->v = addv3(a->v, scalev3( a->bounciness, downv4(displacea) ) );
}
if(b->mass > 0){
vec4 displaceb = scalev4(bdisplacefactor, penvec);
vec3 b_relvel = subv3(b->v, comvel);
vec3 b_planarvel = subv3(b_relvel, //brelvel - portion of brelvel in the direction of penvecnormalized
scalev3(
dotv3(b_relvel, penvecnormalized), //the component in that direction
penvecnormalized //that direction
)
);
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(comvel, scalev3(1-friction, b_planarvel) ); //The center of mass velocity, plus a portion of coplanar velocity.
b->v = addv3(b->v, scalev3( b->bounciness, downv4(displaceb) ) );
}
}
#endif