diff options
Diffstat (limited to 'draw/draw_mesh.c')
| -rw-r--r-- | draw/draw_mesh.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/draw/draw_mesh.c b/draw/draw_mesh.c index 05f5d290..c266bfaa 100644 --- a/draw/draw_mesh.c +++ b/draw/draw_mesh.c @@ -18,17 +18,21 @@ static int clipx(float val, int ismax, const float *v1, const float *v2, int n, { float t; int i; + int v1o = ismax ? v1[0] > val : v1[0] < val; int v2o = ismax ? v2[0] > val : v2[0] < val; + if (v1o + v2o == 0) { /* Both ends of the line are valid - keep v2, v1 will be kept by another call */ copy_vert(dst, v2, n); return 1; } + if (v1o + v2o == 2) /* Both ends are invalid - drop both */ return 0; + /* It is tempting to spot that the second intersection finding * operation below can be reversed so that it's in the same form as * the first one. Do not do this, as the vagaries of floating point @@ -42,7 +46,9 @@ static int clipx(float val, int ismax, const float *v1, const float *v2, int n, for (i = 2; i < n; i++) dst[i] = v1[i] + t * (v2[i] - v1[i]); return 1; - } else { + } + else + { /* v2 valid, v1 invalid - Keep intersection, plus v2 */ t = (val - v2[0]) / (v1[0] - v2[0]); dst[0] = val; @@ -62,17 +68,21 @@ static int clipy(float val, int ismax, const float *v1, const float *v2, int n, { float t; int i; + int v1o = ismax ? v1[1] > val : v1[1] < val; int v2o = ismax ? v2[1] > val : v2[1] < val; + if (v1o + v2o == 0) { /* Both ends of the line are valid - keep v2, v1 will be kept by another call */ copy_vert(dst, v2, n); return 1; } + if (v1o + v2o == 2) /* Both ends are invalid - drop both */ return 0; + /* It is tempting to spot that the second intersection finding * operation below can be reversed so that it's in the same form as * the first one. Do not do this, as the vagaries of floating point @@ -86,7 +96,9 @@ static int clipy(float val, int ismax, const float *v1, const float *v2, int n, for (i = 2; i < n; i++) dst[i] = v1[i] + t * (v2[i] - v1[i]); return 1; - } else { + } + else + { /* v2 valid, v1 invalid - Keep intersection, plus v2 */ t = (val - v2[1]) / (v1[1] - v2[1]); dst[0] = v2[0] + t * (v1[0] - v2[0]); @@ -112,17 +124,21 @@ static int clip_poly(float src[MAXV][MAXN], cp = 0; if (isy) + { for (v2 = 0; v2 < len; v2++) { cp += clipy(val, ismax, src[v1], src[v2], n, dst[cp]); v1 = v2; } + } else + { for (v2 = 0; v2 < len; v2++) { cp += clipx(val, ismax, src[v1], src[v2], n, dst[cp]); v1 = v2; } + } return cp; } |