diff options
Diffstat (limited to 'src/libs/puddle')
| -rw-r--r-- | src/libs/puddle/puddle.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/src/libs/puddle/puddle.c b/src/libs/puddle/puddle.c index e5c0dd4..c6833f7 100644 --- a/src/libs/puddle/puddle.c +++ b/src/libs/puddle/puddle.c @@ -106,9 +106,9 @@ static inline float lerp(float a, float b, float t) /* Sample the supplied puddle field at the specified coordinate. * - * The puddle field is treated as a unit square mapped to the specified - * dimensions @ create time. the sampled value is linearly interpolated from - * the data. + * The puddle field is treated as an unsigned unit square mapped to the + * specified dimensions @ create time. the sampled value is linearly + * interpolated from the data. (coordinates range 0..1) */ float puddle_sample(const puddle_t *puddle, const v2f_t *coordinate) { @@ -118,8 +118,8 @@ float puddle_sample(const puddle_t *puddle, const v2f_t *coordinate) assert(puddle); assert(coordinate); - x = .5f + (coordinate->x * .5f + .5f) * (puddle->w - 2); - y = .5f + (coordinate->y * .5f + .5f) * (puddle->h - 2); + x = .5f + coordinate->x * (puddle->w - 2); + y = .5f + coordinate->y * (puddle->h - 2); x0 = floorf(x); y0 = floorf(y); @@ -130,7 +130,10 @@ float puddle_sample(const puddle_t *puddle, const v2f_t *coordinate) tx = x - (float)x0; ty = y - (float)y0; - return lerp(lerp(puddle->a[y0 * puddle->w + x0], puddle->a[y0 * puddle->w + x1], tx), - lerp(puddle->a[y1 * puddle->w + x0], puddle->a[y1 * puddle->w + x1], tx), + y0 *= puddle->w; + y1 *= puddle->w; + + return lerp(lerp(puddle->a[y0 + x0], puddle->a[y0 + x1], tx), + lerp(puddle->a[y1 + x0], puddle->a[y1 + x1], tx), ty); } |