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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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27
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
v->x *= SCALE; /* Here we try to decide if the vector is too small and would cause
v->y *= SCALE; inaccurate result due to very its inaccurate length. If so, we scale
v->z *= SCALE; it up. We can't scale up everything as big vectors overflow in length
calculations. */
// ^ This pre-scale prevents inaccuracy with very small vectors ([1,1,1]).
if (S3L_abs(v->x + v->y + v->z) < LIMIT)
{
v->x *= SCALE;
v->y *= SCALE;
v->z *= SCALE;
}
#undef SCALE #undef SCALE
#undef LIMIT
S3L_Unit l = S3L_vec3Length(*v); S3L_Unit l = S3L_vec3Length(*v);