# Fresnel reflection problem

**URL:** <https://forums.chaos.com/t/fresnel-reflection-problem/85227>\
**Category:** Issues\
**Created:** [October 10, 2017, 4:10pm UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227 "2017-10-10T16:10:18Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![Crayox13](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/crayox13/32/64242_2.png) [@Crayox13](https://forums.chaos.com/u/Crayox13)\
**Post date:** [October 10, 2017, 4:10pm UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/1 "2017-10-10T16:10:18Z")

</div>

This is probably math but I have fresnel reflection on the floor and it reflects my windows. I like it but I know client will say it’s too strong, so I reduce the refl value and instead of dimming the reflection it either disappears or it reduces the angle somehow meaning it reflects a smaller portion of the window. Any ideas? I also trie using vrayblend material and under blend amount put fallof map with fresnel selected and I get the same result.

---

<div class="post-metadata">

**Author:** ![vlado](https://avatars.discourse-cdn.com/v4/letter/v/779978/32.png) [@vlado](https://forums.chaos.com/u/vlado)\
**Post date:** [October 11, 2017, 5:07am UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/2 "2017-10-11T05:07:22Z")

</div>

Try setting the cutoff threshold in the material options to 0 and see if it helps?

Best regards,  
Vlado

---

<div class="post-metadata">

**Author:** ![vlado](https://avatars.discourse-cdn.com/v4/letter/v/779978/32.png) [@vlado](https://forums.chaos.com/u/vlado)\
**Post date:** [October 11, 2017, 6:21pm UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/3 "2017-10-11T18:21:02Z")

</div>

That’s weird. Can you post that part of the scene?

Best regards,  
Vlado

---

<div class="post-metadata">

**Author:** ![Crayox13](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/crayox13/32/64242_2.png) [@Crayox13](https://forums.chaos.com/u/Crayox13)\
**Post date:** [October 12, 2017, 6:52am UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/4 "2017-10-12T06:52:06Z")

</div>

What do you mean? The part in the red rect. Or settings?

---

<div class="post-metadata">

**Author:** ![vlado](https://avatars.discourse-cdn.com/v4/letter/v/779978/32.png) [@vlado](https://forums.chaos.com/u/vlado)\
**Post date:** [October 12, 2017, 1:51pm UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/5 "2017-10-12T13:51:54Z")

</div>

Sorry, I meant the floor (and its material), the camera, the window and the lighting setup.

Best regards,  
Vlado

---

<div class="post-metadata">

**Author:** ![Crayox13](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/crayox13/32/64242_2.png) [@Crayox13](https://forums.chaos.com/u/Crayox13)\
**Post date:** [October 13, 2017, 10:22am UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/6 "2017-10-13T10:22:28Z")

</div>

I sent the scene to chaos. Try coat material reflection settings 10, 20, 30. The reflection on the floor will shrink instead of dim.

---

<div class="post-metadata">

**Author:** ![Zdravko.Keremidchiev](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/zdravko.keremidchiev/32/48745_2.png) [@Zdravko.Keremidchiev](https://forums.chaos.com/u/Zdravko.Keremidchiev)\
**Post date:** [October 13, 2017, 4:59pm UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/7 "2017-10-13T16:59:33Z")

</div>

The effect is caused by the fall-off map set up. I’m not sure what is the math behind this, I’ll do some more tests.

---

<div class="post-metadata">

**Author:** ![Zdravko.Keremidchiev](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/zdravko.keremidchiev/32/48745_2.png) [@Zdravko.Keremidchiev](https://forums.chaos.com/u/Zdravko.Keremidchiev)\
**Post date:** [October 16, 2017, 1:44pm UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/8 "2017-10-16T13:44:59Z")

</div>

Turns out the culprit is the very high (0.01) Cutoff value of the glass material on the window. Set it to 0.001 and the reflection will behave as expected.

---

<div class="post-metadata">

**Author:** ![Crayox13](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/crayox13/32/64242_2.png) [@Crayox13](https://forums.chaos.com/u/Crayox13)\
**Post date:** [October 17, 2017, 6:59am UTC](https://forums.chaos.com/t/fresnel-reflection-problem/85227/9 "2017-10-17T06:59:12Z")

</div>

Oh! Thank you so much! I’ve been using the same glass and forgot to check IT, was always focused on floor where the refl was.