Has anyone here tried to render a frame using heightmaps and  ibl or sky? In my case i can't render them together because the terrain is super shiny and over reflects the sky, no matter how i tweak the materials it comes out as if it had an almost black roughness map on top of all the materials, like some shinny coating?

Will post a picture tomorrow because right now i'm rendering and still have like 100 frames left

I ran into that as well, and what I did was adjust the parameters for the Iray material of the terrain.

Select the terrain and then the Iray Render option, Material section. The four material maps of the terrain will be listed as Map01, Map02, Map03, Map04.



If I recall correctly, the Roughness multiplier was much higher than 1.0.

In the sample render below, I use IBL and a sky. Apart from one directional light, IBL is the only lighting.



The road is part of the terrain and was particularly tricky to get right.

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I'll be damned, can't reproduce it anymore, i guess i found a one time only bug.

Aha! here it is:

the only way to fix this is to completely kill roughness and metallic in the iray material tab

I checked my iClone texture settings. and I have indeed Roughness white and Metallic black.

I tried some Roughness for the street and that worked OK. My sky is quite dark and the direct light actually contributed more to the shininess than the IBL.

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iClone Terrains use sort of hybrid materials. PBR/Traditional. They have Roughness and Metallic slots (which are empty by default), yet they also have sliders for Secular and Roughness.
Even if you fill Roughness and Metallic slots in iClone, it is not enough to defeat shininess 100% (so we end up tweaking Iray material, which we should not).
Shininess is not apparent under certain angles, which makes it even more confusing.

So it seems to me like a bug in special "HeightMap" MDL (RL_Terrain.mdl) material developed by RL, where they were not thorough by not looking at the result from different camera angles with different sky objects.