I've been experimenting/coding a PBR implementation (BRDF) on a basic landscape and use the sky texture as an influence for application of light.  But my dusk and dawn the terrain colors are overly saturated with orange/brown from my sky textures and/or my whites (like snow) would turn brown.  The sky looks great but the terrain and/or any objects with PBR supporting materials reflect way too much of the sky color.  Problem is, if I dial that down then the saturation and specular is off during day time (far too dull) ... adjust for one time of day and mess up another.

Of course, Ray Tracing extensions in DX12 could obviously help but it's still not going to solve my dusk/dawn PBR issues ... that seems to be more fundamental. 

So I guess my question is, how can I get PBR to look good at all times of the day/night (especially dawn/dusk)?  I've gone thru Matt Pharr's book but haven't really found anything that could help me with this specific issue of whites (specifically snow textures).

Thoughts?

Cheers, Rob.

Also note that most of PBR materials we can find do not come from physical measurements. Thus they might not reflect well real-world matters.

Thanks for the responses, unfortunately other projects have taken precedence so I've put this on the back burner for now to revisit at a later date.  

9 hours ago, LorenzoGatti said:

Really physically correct rendering would have the sun as the only light source

Actually no, I'm using Sun, Moon, stars/Milky Way and "ground" lights as sources.

On 2/5/2019 at 12:12 AM, _Silence_ said:

Also note that most of PBR materials we can find do not come from physical measurements.

I thought "Substance" suite was exactly that? 

On 2/5/2019 at 2:09 AM, turanszkij said:

you could also double check your gamma

Unfortunately gamma is too global ... I did experiment with "multiple" light source (invisible suns) at various opposing positions and that did actually help but not sure it looked as "natural" as I'd like.

I honestly haven't tried DX12 RTX extensions for Ray Tracing for my primary light sources (sun, moon, stars/Milky Way) ... but my understanding is that wouldn't be viable for large scale globe/terrain situations?

Anyway, appreciate all the responses and when I have some time I'll return to this project.

Cheers, Rob.

38 minutes ago, Rob Ainscough said:

I thought "Substance" suite was exactly that? 

Well I don't know. After a quick look over their website, I haven't seen any such mention. But just this:

Quote

All materials have been developed with physically based workflows in mind.

From what I know, this is quite complicated, time consuming and also expensive to have real good reflectance BRDF and such. We had one room dedicated to this in a previous company. And most of our clients were sending us samples of their matters instead of trying to do them on their own.

46 minutes ago, Rob Ainscough said:

Actually no, I'm using Sun, Moon, stars/Milky Way and "ground" lights as sources.

 

Lighting matters a lot too. If you want realistic sky lighting, the CIE norms are where to have a look. But this isn't a little thing...

Finally, one easy thing you can do is to trick ambient occlusion and roughness. You can also find on the internet some BRDF libraries where common materials are listed.