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Fix vector normalization overflows

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This commit is contained in:
Miloslav Číž 2019-06-29 23:05:14 +02:00
parent c14338ce84
commit f7ec996b60
1 changed files with 20 additions and 7 deletions
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21
small3dlib.h
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@ -319,7 +319,12 @@ static inline void S3L_setVec4(S3L_Vec4 *v, S3L_Unit x, S3L_Unit y,
static inline void S3L_vec3Add(S3L_Vec4 *result, S3L_Vec4 added); static inline void S3L_vec3Add(S3L_Vec4 *result, S3L_Vec4 added);
static inline void S3L_vec3Sub(S3L_Vec4 *result, S3L_Vec4 substracted); static inline void S3L_vec3Sub(S3L_Vec4 *result, S3L_Vec4 substracted);
S3L_Unit S3L_vec3Length(S3L_Vec4 v); S3L_Unit S3L_vec3Length(S3L_Vec4 v);
/** Normalizes Vec3. Note that this function tries to normalize correctly rather
than quickly! If you need to normalize quickly, do it yourself in a way that
best fits your case. */
void S3L_normalizeVec3(S3L_Vec4 *v); void S3L_normalizeVec3(S3L_Vec4 *v);
S3L_Unit S3L_vec2Length(S3L_Vec4 v); S3L_Unit S3L_vec2Length(S3L_Vec4 v);
void S3L_normalizeVec2(S3L_Vec4 *v); void S3L_normalizeVec2(S3L_Vec4 *v);
void S3L_crossProduct(S3L_Vec4 a, S3L_Vec4 b, S3L_Vec4 *result); void S3L_crossProduct(S3L_Vec4 a, S3L_Vec4 b, S3L_Vec4 *result);
@ -954,8 +959,7 @@ void S3L_crossProduct(S3L_Vec4 a, S3L_Vec4 b, S3L_Vec4 *result)
result->z = a.x * b.y - a.y * b.x; result->z = a.x * b.y - a.y * b.x;
} }
void S3L_triangleNormal(S3L_Vec4 t0, S3L_Vec4 t1, S3L_Vec4 t2, void S3L_triangleNormal(S3L_Vec4 t0, S3L_Vec4 t1, S3L_Vec4 t2, S3L_Vec4 *n)
S3L_Vec4 *n)
{ {
#define antiOverflow 32 #define antiOverflow 32
@ -970,6 +974,7 @@ void S3L_triangleNormal(S3L_Vec4 t0, S3L_Vec4 t1, S3L_Vec4 t2,
#undef antiOverflow #undef antiOverflow
S3L_crossProduct(t1,t2,n); S3L_crossProduct(t1,t2,n);
S3L_normalizeVec3(n); S3L_normalizeVec3(n);
} }
@ -1449,14 +1454,22 @@ S3L_Unit S3L_vec2Length(S3L_Vec4 v)
void S3L_normalizeVec3(S3L_Vec4 *v) void S3L_normalizeVec3(S3L_Vec4 *v)
{ {
#define SCALE 16 #define SCALE 16
#define LIMIT 16
/* Here we try to decide if the vector is too small and would cause
inaccurate result due to very its inaccurate length. If so, we scale
it up. We can't scale up everything as big vectors overflow in length
calculations. */
if (S3L_abs(v->x + v->y + v->z) < LIMIT)
{
v->x *= SCALE; v->x *= SCALE;
v->y *= SCALE; v->y *= SCALE;
v->z *= SCALE; v->z *= SCALE;
}
// ^ This pre-scale prevents inaccuracy with very small vectors ([1,1,1]).
#undef SCALE #undef SCALE
#undef LIMIT
S3L_Unit l = S3L_vec3Length(*v); S3L_Unit l = S3L_vec3Length(*v);