Fix T82988: Div by zero with curve deform modifier

In `calc_curve_deform` a factor is calculated without checking if
the divisior is zero or close to zero. This patch adds the missing
checks and sets the factor to zero if the division shouldn't be
computed.

Reviewed By: mont29

Differential Revision: https://developer.blender.org/D9645

1 files changed, 20 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/lattice.c b/source/blender/blenkernel/intern/lattice.c
index d371af93bb7..34216e08650 100644
--- a/source/blender/blenkernel/intern/lattice.c
+++ b/source/blender/blenkernel/intern/lattice.c
@@ -664,16 +664,33 @@ static bool calc_curve_deform(
   if (is_neg_axis) {
     index = axis - 3;
     if (cu->flag & CU_STRETCH) {
-      fac = -(co[index] - cd->dmax[index]) / (cd->dmax[index] - cd->dmin[index]);
+      const float divisor = cd->dmax[index] - cd->dmin[index];
+      if (LIKELY(divisor > FLT_EPSILON)) {
+        fac = -(co[index] - cd->dmax[index]) / divisor;
+      }
+      else {
+        fac = 0.0f;
+      }
     }
     else {
-      fac = -(co[index] - cd->dmax[index]) / (par->runtime.curve_cache->path->totdist);
+      if (LIKELY(par->runtime.curve_cache->path->totdist > FLT_EPSILON)) {
+        fac = -(co[index] - cd->dmax[index]) / (par->runtime.curve_cache->path->totdist);
+      }
+      else {
+        fac = 0.0f;
+      }
     }
   }
   else {
     index = axis;
     if (cu->flag & CU_STRETCH) {
-      fac = (co[index] - cd->dmin[index]) / (cd->dmax[index] - cd->dmin[index]);
+      const float divisor = cd->dmax[index] - cd->dmin[index];
+      if (LIKELY(divisor > FLT_EPSILON)) {
+        fac = (co[index] - cd->dmin[index]) / divisor;
+      }
+      else {
+        fac = 0.0f;
+      }
     }
     else {
       if (LIKELY(par->runtime.curve_cache->path->totdist > FLT_EPSILON)) {