return min + (f32)q * ((max-min) / (f32)mask);
}
+/* https://iquilezles.org/articles/functions/
+ *
+ * Use k to control the stretching of the function. Its maximum, which is 1,
+ * happens at exactly x = 1/k.
+ */
+static f32 vg_exp_impulse( f32 x, f32 k ){
+ f32 h = k*x;
+ return h*expf(1.0f-h);
+}
+
/*
* -----------------------------------------------------------------------------
* Section 2.a 2D Vectors
v3_cross( n, tx, ty );
}
+/*
+ * Compute yaw and pitch based of a normalized vector representing forward
+ * forward: -z
+ * result -> (YAW,PITCH,0.0)
+ */
+static void v3_angles( v3f v, v3f out_angles ){
+ float yaw = atan2f( v[0], -v[2] ),
+ pitch = atan2f(
+ -v[1],
+ sqrtf(
+ v[0]*v[0] + v[2]*v[2]
+ )
+ );
+
+ out_angles[0] = yaw;
+ out_angles[1] = pitch;
+ out_angles[2] = 0.0f;
+}
+
+/*
+ * Compute the forward vector from (YAW,PITCH,ROLL)
+ * forward: -z
+ */
+static void v3_angles_vector( v3f angles, v3f out_v ){
+ out_v[0] = sinf( angles[0] ) * cosf( angles[1] );
+ out_v[1] = -sinf( angles[1] );
+ out_v[2] = -cosf( angles[0] ) * cosf( angles[1] );
+}
/*
* -----------------------------------------------------------------------------
v3_add( v1, v2, d );
}
-static f32 q_dist( v4f q0, v3f q1 ){
+static f32 q_dist( v4f q0, v4f q1 ){
return acosf( 2.0f * v4_dot(q0,q1) -1.0f );
}
/* changes to STATE_VECTOR_LENGTH also require changes to this */
#define MT_STATE_VECTOR_M 397
-struct {
+typedef struct vg_rand vg_rand;
+struct vg_rand {
u32 mt[MT_STATE_VECTOR_LENGTH];
i32 index;
-}
-static vg_rand;
+};
-static void vg_rand_seed( unsigned long seed )
-{
+static void vg_rand_seed( vg_rand *rand, unsigned long seed ) {
/* set initial seeds to mt[STATE_VECTOR_LENGTH] using the generator
* from Line 25 of Table 1 in: Donald Knuth, "The Art of Computer
* Programming," Vol. 2 (2nd Ed.) pp.102.
*/
- vg_rand.mt[0] = seed & 0xffffffff;
- for( vg_rand.index=1; vg_rand.index<MT_STATE_VECTOR_LENGTH; vg_rand.index++){
- vg_rand.mt[vg_rand.index] =
- (6069 * vg_rand.mt[vg_rand.index-1]) & 0xffffffff;
+ rand->mt[0] = seed & 0xffffffff;
+ for( rand->index=1; rand->index<MT_STATE_VECTOR_LENGTH; rand->index++){
+ rand->mt[rand->index] = (6069 * rand->mt[rand->index-1]) & 0xffffffff;
}
}
/*
* Generates a pseudo-randomly generated long.
*/
-static u32 vg_randu32(void)
-{
+static u32 vg_randu32( vg_rand *rand ) {
u32 y;
/* mag[x] = x * 0x9908b0df for x = 0,1 */
static u32 mag[2] = {0x0, 0x9908b0df};
- if( vg_rand.index >= MT_STATE_VECTOR_LENGTH || vg_rand.index < 0 ){
+ if( rand->index >= MT_STATE_VECTOR_LENGTH || rand->index < 0 ){
/* generate STATE_VECTOR_LENGTH words at a time */
int kk;
- if( vg_rand.index >= MT_STATE_VECTOR_LENGTH+1 || vg_rand.index < 0 ){
- vg_rand_seed( 4357 );
+ if( rand->index >= MT_STATE_VECTOR_LENGTH+1 || rand->index < 0 ){
+ vg_rand_seed( rand, 4357 );
}
for( kk=0; kk<MT_STATE_VECTOR_LENGTH-MT_STATE_VECTOR_M; kk++ ){
- y = (vg_rand.mt[kk] & MT_UPPER_MASK) |
- (vg_rand.mt[kk+1] & MT_LOWER_MASK);
- vg_rand.mt[kk] = vg_rand.mt[kk+MT_STATE_VECTOR_M] ^
- (y >> 1) ^ mag[y & 0x1];
+ y = (rand->mt[kk] & MT_UPPER_MASK) |
+ (rand->mt[kk+1] & MT_LOWER_MASK);
+ rand->mt[kk] = rand->mt[kk+MT_STATE_VECTOR_M] ^ (y>>1) ^ mag[y & 0x1];
}
for( ; kk<MT_STATE_VECTOR_LENGTH-1; kk++ ){
- y = (vg_rand.mt[kk] & MT_UPPER_MASK) |
- (vg_rand.mt[kk+1] & MT_LOWER_MASK);
- vg_rand.mt[kk] =
- vg_rand.mt[ kk+(MT_STATE_VECTOR_M-MT_STATE_VECTOR_LENGTH)] ^
+ y = (rand->mt[kk] & MT_UPPER_MASK) |
+ (rand->mt[kk+1] & MT_LOWER_MASK);
+ rand->mt[kk] =
+ rand->mt[ kk+(MT_STATE_VECTOR_M-MT_STATE_VECTOR_LENGTH)] ^
(y >> 1) ^ mag[y & 0x1];
}
- y = (vg_rand.mt[MT_STATE_VECTOR_LENGTH-1] & MT_UPPER_MASK) |
- (vg_rand.mt[0] & MT_LOWER_MASK);
- vg_rand.mt[MT_STATE_VECTOR_LENGTH-1] =
- vg_rand.mt[MT_STATE_VECTOR_M-1] ^ (y >> 1) ^ mag[y & 0x1];
- vg_rand.index = 0;
+ y = (rand->mt[MT_STATE_VECTOR_LENGTH-1] & MT_UPPER_MASK) |
+ (rand->mt[0] & MT_LOWER_MASK);
+ rand->mt[MT_STATE_VECTOR_LENGTH-1] =
+ rand->mt[MT_STATE_VECTOR_M-1] ^ (y >> 1) ^ mag[y & 0x1];
+ rand->index = 0;
}
- y = vg_rand.mt[vg_rand.index++];
+ y = rand->mt[rand->index++];
y ^= (y >> 11);
y ^= (y << 7) & MT_TEMPERING_MASK_B;
y ^= (y << 15) & MT_TEMPERING_MASK_C;
/*
* Generates a pseudo-randomly generated f64 in the range [0..1].
*/
-static inline f64 vg_randf64(void)
-{
- return (f64)vg_randu32()/(f64)0xffffffff;
+static inline f64 vg_randf64( vg_rand *rand ){
+ return (f64)vg_randu32(rand)/(f64)0xffffffff;
}
-static inline f64 vg_randf64_range( f64 min, f64 max )
-{
- return vg_lerp( min, max, (f64)vg_randf64() );
+static inline f64 vg_randf64_range( vg_rand *rand, f64 min, f64 max ){
+ return vg_lerp( min, max, (f64)vg_randf64(rand) );
}
-static inline void vg_rand_dir( v3f dir )
-{
- dir[0] = vg_randf64();
- dir[1] = vg_randf64();
- dir[2] = vg_randf64();
+static inline void vg_rand_dir( vg_rand *rand, v3f dir ){
+ dir[0] = vg_randf64(rand);
+ dir[1] = vg_randf64(rand);
+ dir[2] = vg_randf64(rand);
+
+ /* warning: *could* be 0 length.
+ * very unlikely.. 1 in (2^32)^3. but its mathematically wrong. */
v3_muls( dir, 2.0f, dir );
v3_sub( dir, (v3f){1.0f,1.0f,1.0f}, dir );
v3_normalize( dir );
}
-static inline void vg_rand_sphere( v3f co )
-{
- vg_rand_dir(co);
- v3_muls( co, cbrtf( vg_randf64() ), co );
+static inline void vg_rand_sphere( vg_rand *rand, v3f co ){
+ vg_rand_dir(rand,co);
+ v3_muls( co, cbrtf( vg_randf64(rand) ), co );
+}
+
+static void vg_rand_disc( vg_rand *rand, v2f co ){
+ f32 a = vg_randf64(rand) * VG_TAUf;
+ co[0] = sinf(a);
+ co[1] = cosf(a);
+ v2_muls( co, sqrtf( vg_randf64(rand) ), co );
+}
+
+static void vg_rand_cone( vg_rand *rand, v3f out_dir, f32 angle ){
+ f32 r = sqrtf(vg_randf64(rand)) * angle * 0.5f,
+ a = vg_randf64(rand) * VG_TAUf;
+
+ out_dir[0] = sinf(a) * sinf(r);
+ out_dir[1] = cosf(a) * sinf(r);
+ out_dir[2] = cosf(r);
}
#endif /* VG_M_H */