diff --git a/data/shader/flame.gsh b/data/shader/flame.gsh
index 61aa9af..fd15c17 100644
--- a/data/shader/flame.gsh
+++ b/data/shader/flame.gsh
@@ -29,7 +29,7 @@ const float begin_2   = 0;
 const float end_2     = 3;
 
 float flickerFunction() {
-    return sin(time);
+    return pow(0.6*sin(10.0*time), 2) + 0.4;
 }
 
 float radiusFunction(float x) {
diff --git a/data/shader/phong.fsh b/data/shader/phong.fsh
index e22c325..f11f9d3 100644
--- a/data/shader/phong.fsh
+++ b/data/shader/phong.fsh
@@ -65,7 +65,7 @@ vec2 poissonDisk[16] = vec2[](
 );
 
 float flickerFunction() {
-    return sin(time);
+    return pow(0.6*sin(10.0*time), 2) + 0.4;
 }
 
 float sampleDirectionalShadow(sampler2DShadow shadowMap, vec4 shadowCoord, float maxBias ) {