Hello guys.

I have a problem and I can't figure out what might be causing it.

If I create a new scene, the GI light is working just right. But if I create this light in a scene I'm currently working on, I get:
Failed to open temp:gilight1.pmap
error message appearing in Houdini Console and I loose all indirect lighting on my objects.

For what it's worth, all objects in the scene use Disney BSDF shader (http://forums.odforce.net/topic/20682-bsdf-bonanza-ggx-microfacets-disney-brdf-and-more/) [forums.odforce.net] , one area light and an HDR environment light. But I don't think the shader has anything to do with the problem, because if I apply the default mantra surface shader to all objects in the scene, I still get this error.

However, if I remove all objects from the scene and put a simple geo, like torus or grid, and add an envlight along with a GI light, it works.
Could it be that the scene got corrupted somehow?

Looks like indirect light likes to have at least one standard light in the scene, even if there's an HDR environment light already present. I had an area light, but had I turned its intensity down to 0. Pumping it up to > 0 got rid of this strange error.

Disabling area light with “Light Enabled” flag, also seems to cause this problem.

Can anyone explain to me why does this happen? Lights emit direct light and photons, but (theoretically) so does environment light. So why turning the light off or not having standard light at all causes this problem with GI, when environment light can still contribute to the light model? Or maybe environment light does not shoot photons in Houdini? And, most importantly, why the write error of the photon map?

To be honest most users have moved on from the GI light > embrace PBR !

Rob

So, diffuse bounces (Diffuse Limit) can fully replace GI in PBR?
If so, then… cool!

But what about interior scenes? Say I want to use an envlight and portal lights. Will PBR with adequate diffuse limit be enough to give me good lighting in dark corners without GI?

Is GI obsolete now?