Add assertion to avoid passing negative value to sqrt().

fangguanya · Mar 9, 2017 · 525a3ee · 525a3ee
1 parent 2d76f2f
commit 525a3ee
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/src/cameras/realistic.cpp b/src/cameras/realistic.cpp
@@ -452,9 +452,10 @@ Float RealisticCamera::FocusThickLens(Float focusDistance) {
     // Compute translation of lens, _delta_, to focus at _focusDistance_
     Float f = fz[0] - pz[0];
     Float z = -focusDistance;
+    Float c = (pz[1] - z - pz[0]) * (pz[1] - z * 4 * f - pz[0]);
+    CHECK_GT(c, 0) << "Coefficient must be positive. It looks focusDistance: " << focusDistance << " is too short for a given lenses configuration";
     Float delta =
-        0.5f * (pz[1] - z + pz[0] -
-                std::sqrt((pz[1] - z - pz[0]) * (pz[1] - z - 4 * f - pz[0])));
+        0.5f * (pz[1] - z + pz[0] - std::sqrt(c));
     return elementInterfaces.back().thickness + delta;
 }