Merge pull request #604 from pzgulyas/headlight

Fix headlight flickering when switching down from bright to dim

Author: pzgulyas

Source/RunActivity/Viewer3D/Shaders.cs

@@ -205,7 +205,7 @@ public void SetLightVector_ZFar(Vector3 sunDirection, int zFar)
         public void SetHeadlight(ref Vector3 position, ref Vector3 direction, float distance, float minDotProduct, float fadeTime, float fadeDuration, float clampValue, ref Vector4 color)
         {
             var lighting = fadeTime / fadeDuration * clampValue;
-            if (lighting < 0) lighting = 1 + lighting;
+            if (fadeDuration < 0) lighting = 1 + lighting;
             headlightPosition.SetValue(new Vector4(position, MathHelper.Clamp(lighting, 0, clampValue)));
             headlightDirection.SetValue(new Vector4(direction, 0.5f * (1 - minDotProduct))); // We want 50% brightness at the given dot product.
             headlightRcpDistance.SetValue(1f / distance); // Needed to be separated (direction * distance) because no pre-shaders are supported in XNA 4