2 * Resources: Box2D - Erin Catto
7 static void rb_tangent_basis( v3f n
, v3f tx
, v3f ty
);
16 #define k_rb_delta (1.0f/60.0f)
18 typedef struct rigidbody rigidbody
;
30 float bias
, norm_impulse
, tangent_impulse
[2];
35 v3f delta
; /* where is the origin of this in relation to a parent body */
36 m4x3f to_world
, to_local
;
39 static void rb_update_transform( rigidbody
*rb
)
42 q_m3x3( rb
->q
, rb
->to_world
);
43 v3_copy( rb
->co
, rb
->to_world
[3] );
45 m4x3_invert_affine( rb
->to_world
, rb
->to_local
);
48 static void rb_init( rigidbody
*rb
)
55 v3_sub( rb
->bbx
[1], rb
->bbx
[0], dims
);
57 rb
->inv_mass
= 1.0f
/(8.0f
*dims
[0]*dims
[1]*dims
[2]);
59 rb_update_transform( rb
);
62 static void rb_iter( rigidbody
*rb
)
64 v3f gravity
= { 0.0f
, -9.6f
, 0.0f
};
65 v3_muladds( rb
->v
, gravity
, k_rb_delta
, rb
->v
);
67 /* intergrate velocity */
68 v3_muladds( rb
->co
, rb
->v
, k_rb_delta
, rb
->co
);
70 v3_lerp( rb
->I
, (v3f
){0.0f
,0.0f
,0.0f
}, 0.0025f
, rb
->I
);
72 /* inegrate inertia */
73 if( v3_length2( rb
->I
) > 0.0f
)
77 v3_copy( rb
->I
, axis
);
79 float mag
= v3_length( axis
);
80 v3_divs( axis
, mag
, axis
);
81 q_axis_angle( rotation
, axis
, mag
*k_rb_delta
);
82 q_mul( rotation
, rb
->q
, rb
->q
);
86 static void rb_torque( rigidbody
*rb
, v3f axis
, float mag
)
88 v3_muladds( rb
->I
, axis
, mag
*k_rb_delta
, rb
->I
);
91 static void rb_tangent_basis( v3f n
, v3f tx
, v3f ty
)
93 /* Compute tangent basis (box2d) */
94 if( fabsf( n
[0] ) >= 0.57735027f
)
108 v3_cross( n
, tx
, ty
);
111 static void rb_build_manifold( rigidbody
*rb
)
115 float *p000
= pts
[0], *p001
= pts
[1], *p010
= pts
[2], *p011
= pts
[3],
116 *p100
= pts
[4], *p101
= pts
[5], *p110
= pts
[6], *p111
= pts
[7];
118 p000
[0]=box
[0][0];p000
[1]=box
[0][1];p000
[2]=box
[0][2];
119 p001
[0]=box
[0][0];p001
[1]=box
[0][1];p001
[2]=box
[1][2];
120 p010
[0]=box
[0][0];p010
[1]=box
[1][1];p010
[2]=box
[0][2];
121 p011
[0]=box
[0][0];p011
[1]=box
[1][1];p011
[2]=box
[1][2];
123 p100
[0]=box
[1][0];p100
[1]=box
[0][1];p100
[2]=box
[0][2];
124 p101
[0]=box
[1][0];p101
[1]=box
[0][1];p101
[2]=box
[1][2];
125 p110
[0]=box
[1][0];p110
[1]=box
[1][1];p110
[2]=box
[0][2];
126 p111
[0]=box
[1][0];p111
[1]=box
[1][1];p111
[2]=box
[1][2];
128 m4x3_mulv( rb
->to_world
, p000
, p000
);
129 m4x3_mulv( rb
->to_world
, p001
, p001
);
130 m4x3_mulv( rb
->to_world
, p010
, p010
);
131 m4x3_mulv( rb
->to_world
, p011
, p011
);
132 m4x3_mulv( rb
->to_world
, p100
, p100
);
133 m4x3_mulv( rb
->to_world
, p101
, p101
);
134 m4x3_mulv( rb
->to_world
, p110
, p110
);
135 m4x3_mulv( rb
->to_world
, p111
, p111
);
137 rb
->manifold_count
= 0;
139 for( int i
=0; i
<8; i
++ )
141 float *point
= pts
[i
];
142 struct contact
*ct
= &rb
->manifold
[rb
->manifold_count
];
145 v3_copy( point
, surface
);
150 if( !ray_world( surface
, (v3f
){0.0f
,-1.0f
,0.0f
}, &hit
))
153 v3_copy( hit
.normal
, ct
->n
);
154 v3_copy( hit
.pos
, surface
);
156 float p
= vg_minf( surface
[1] - point
[1], 1.0f
);
160 v3_add( point
, surface
, ct
->co
);
161 v3_muls( ct
->co
, 0.5f
, ct
->co
);
163 //vg_line_pt3( ct->co, 0.0125f, 0xff0000ff );
165 v3_sub( ct
->co
, rb
->co
, ct
->delta
);
166 ct
->bias
= -0.2f
* (1.0f
/k_rb_delta
) * vg_minf( 0.0f
, -p
+0.04f
);
167 rb_tangent_basis( ct
->n
, ct
->t
[0], ct
->t
[1] );
169 ct
->norm_impulse
= 0.0f
;
170 ct
->tangent_impulse
[0] = 0.0f
;
171 ct
->tangent_impulse
[1] = 0.0f
;
173 rb
->manifold_count
++;
174 if( rb
->manifold_count
== 4 )
180 static void rb_constraint_manifold( rigidbody
*rb
)
182 float k_friction
= 0.1f
;
184 /* Friction Impulse */
185 for( int i
=0; i
<rb
->manifold_count
; i
++ )
187 struct contact
*ct
= &rb
->manifold
[i
];
190 v3_cross( rb
->I
, ct
->delta
, dv
);
191 v3_add( rb
->v
, dv
, dv
);
193 for( int j
=0; j
<2; j
++ )
195 float vt
= vg_clampf( -v3_dot( dv
, ct
->t
[j
] ),
196 -k_friction
, k_friction
);
198 vt
= -v3_dot( dv
, ct
->t
[j
] );
200 float temp
= ct
->tangent_impulse
[j
];
201 ct
->tangent_impulse
[j
] = vg_clampf( temp
+vt
, -k_friction
, k_friction
);
202 vt
= ct
->tangent_impulse
[j
] - temp
;
206 v3_muls( ct
->t
[j
], vt
, impulse
);
207 v3_add( impulse
, rb
->v
, rb
->v
);
208 v3_cross( ct
->delta
, impulse
, impulse
);
209 v3_add( impulse
, rb
->I
, rb
->I
);
214 for( int i
=0; i
<rb
->manifold_count
; i
++ )
216 struct contact
*ct
= &rb
->manifold
[i
];
219 v3_cross( rb
->I
, ct
->delta
, dv
);
220 v3_add( rb
->v
, dv
, dv
);
222 float vn
= -v3_dot( dv
, ct
->n
);
225 float temp
= ct
->norm_impulse
;
226 ct
->norm_impulse
= vg_maxf( temp
+ vn
, 0.0f
);
227 vn
= ct
->norm_impulse
- temp
;
231 v3_muls( ct
->n
, vn
, impulse
);
232 v3_add( impulse
, rb
->v
, rb
->v
);
233 v3_cross( ct
->delta
, impulse
, impulse
);
234 v3_add( impulse
, rb
->I
, rb
->I
);
238 struct rb_angle_limit
240 rigidbody
*rba
, *rbb
;
245 static int rb_angle_limit_force(
246 rigidbody
*rba
, v3f va
,
247 rigidbody
*rbb
, v3f vb
,
251 m3x3_mulv( rba
->to_world
, va
, wva
);
252 m3x3_mulv( rbb
->to_world
, vb
, wvb
);
254 float dt
= v3_dot(wva
,wvb
)*0.999f
,
259 float correction
= max
-ang
;
262 v3_cross( wva
, wvb
, axis
);
265 q_axis_angle( rotation
, axis
, -correction
*0.25f
);
266 q_mul( rotation
, rba
->q
, rba
->q
);
268 q_axis_angle( rotation
, axis
, correction
*0.25f
);
269 q_mul( rotation
, rbb
->q
, rbb
->q
);
277 static void rb_constraint_angle_limit( struct rb_angle_limit
*limit
)
284 static void rb_constraint_angle( rigidbody
*rba
, v3f va
,
285 rigidbody
*rbb
, v3f vb
,
286 float max
, float spring
)
289 m3x3_mulv( rba
->to_world
, va
, wva
);
290 m3x3_mulv( rbb
->to_world
, vb
, wvb
);
292 float dt
= v3_dot(wva
,wvb
)*0.999f
,
296 v3_cross( wva
, wvb
, axis
);
297 v3_muladds( rba
->I
, axis
, ang
*spring
*0.5f
, rba
->I
);
298 v3_muladds( rbb
->I
, axis
, -ang
*spring
*0.5f
, rbb
->I
);
302 /* TODO: convert max into the dot product value so we dont have to always
303 * evaluate acosf, only if its greater than the angle specified */
307 float correction
= max
-ang
;
310 q_axis_angle( rotation
, axis
, -correction
*0.125f
);
311 q_mul( rotation
, rba
->q
, rba
->q
);
313 q_axis_angle( rotation
, axis
, correction
*0.125f
);
314 q_mul( rotation
, rbb
->q
, rbb
->q
);
318 static void rb_relative_velocity( rigidbody
*ra
, v3f lca
,
319 rigidbody
*rb
, v3f lcb
, v3f rcv
)
322 m3x3_mulv( ra
->to_world
, lca
, wca
);
323 m3x3_mulv( rb
->to_world
, lcb
, wcb
);
325 v3_sub( ra
->v
, rb
->v
, rcv
);
328 v3_cross( ra
->I
, wca
, rcv_Ra
);
329 v3_cross( rb
->I
, wcb
, rcv_Rb
);
330 v3_add( rcv_Ra
, rcv
, rcv
);
331 v3_sub( rcv
, rcv_Rb
, rcv
);
334 static void rb_constraint_position( rigidbody
*ra
, v3f lca
,
335 rigidbody
*rb
, v3f lcb
)
337 /* C = (COa + Ra*LCa) - (COb + Rb*LCb) = 0 */
339 m3x3_mulv( ra
->to_world
, lca
, wca
);
340 m3x3_mulv( rb
->to_world
, lcb
, wcb
);
343 v3_add( wcb
, rb
->co
, delta
);
344 v3_sub( delta
, wca
, delta
);
345 v3_sub( delta
, ra
->co
, delta
);
347 v3_muladds( ra
->co
, delta
, 0.5f
, ra
->co
);
348 v3_muladds( rb
->co
, delta
, -0.5f
, rb
->co
);
351 v3_sub( ra
->v
, rb
->v
, rcv
);
354 v3_cross( ra
->I
, wca
, rcv_Ra
);
355 v3_cross( rb
->I
, wcb
, rcv_Rb
);
356 v3_add( rcv_Ra
, rcv
, rcv
);
357 v3_sub( rcv
, rcv_Rb
, rcv
);
359 float nm
= 0.5f
/(rb
->inv_mass
+ ra
->inv_mass
);
361 float mass_a
= 1.0f
/ra
->inv_mass
,
362 mass_b
= 1.0f
/rb
->inv_mass
,
363 total_mass
= mass_a
+mass_b
;
366 v3_muls( rcv
, 1.0f
, impulse
);
367 v3_muladds( rb
->v
, impulse
, mass_b
/total_mass
, rb
->v
);
368 v3_cross( wcb
, impulse
, impulse
);
369 v3_add( impulse
, rb
->I
, rb
->I
);
371 v3_muls( rcv
, -1.0f
, impulse
);
372 v3_muladds( ra
->v
, impulse
, mass_a
/total_mass
, ra
->v
);
373 v3_cross( wca
, impulse
, impulse
);
374 v3_add( impulse
, ra
->I
, ra
->I
);
378 v3_muls( delta
, 0.5f
*spring
, impulse
);
380 v3_add( impulse
, ra
->v
, ra
->v
);
381 v3_cross( wca
, impulse
, impulse
);
382 v3_add( impulse
, ra
->I
, ra
->I
);
384 v3_muls( delta
, -0.5f
*spring
, impulse
);
386 v3_add( impulse
, rb
->v
, rb
->v
);
387 v3_cross( wcb
, impulse
, impulse
);
388 v3_add( impulse
, rb
->I
, rb
->I
);
392 static void rb_debug( rigidbody
*rb
, u32 colour
)
395 v3f p000
, p001
, p010
, p011
, p100
, p101
, p110
, p111
;
397 p000
[0]=box
[0][0];p000
[1]=box
[0][1];p000
[2]=box
[0][2];
398 p001
[0]=box
[0][0];p001
[1]=box
[0][1];p001
[2]=box
[1][2];
399 p010
[0]=box
[0][0];p010
[1]=box
[1][1];p010
[2]=box
[0][2];
400 p011
[0]=box
[0][0];p011
[1]=box
[1][1];p011
[2]=box
[1][2];
402 p100
[0]=box
[1][0];p100
[1]=box
[0][1];p100
[2]=box
[0][2];
403 p101
[0]=box
[1][0];p101
[1]=box
[0][1];p101
[2]=box
[1][2];
404 p110
[0]=box
[1][0];p110
[1]=box
[1][1];p110
[2]=box
[0][2];
405 p111
[0]=box
[1][0];p111
[1]=box
[1][1];p111
[2]=box
[1][2];
407 m4x3_mulv( rb
->to_world
, p000
, p000
);
408 m4x3_mulv( rb
->to_world
, p001
, p001
);
409 m4x3_mulv( rb
->to_world
, p010
, p010
);
410 m4x3_mulv( rb
->to_world
, p011
, p011
);
411 m4x3_mulv( rb
->to_world
, p100
, p100
);
412 m4x3_mulv( rb
->to_world
, p101
, p101
);
413 m4x3_mulv( rb
->to_world
, p110
, p110
);
414 m4x3_mulv( rb
->to_world
, p111
, p111
);
416 vg_line( p000
, p001
, colour
);
417 vg_line( p001
, p011
, colour
);
418 vg_line( p011
, p010
, colour
);
419 vg_line( p010
, p000
, colour
);
421 vg_line( p100
, p101
, colour
);
422 vg_line( p101
, p111
, colour
);
423 vg_line( p111
, p110
, colour
);
424 vg_line( p110
, p100
, colour
);
426 vg_line( p100
, p000
, colour
);
427 vg_line( p101
, p001
, colour
);
428 vg_line( p110
, p010
, colour
);
429 vg_line( p111
, p011
, colour
);
431 vg_line( p000
, p110
, colour
);
432 vg_line( p100
, p010
, colour
);
435 #endif /* RIGIDBODY_H */