Final solution to GI Flickering needed :)

[cyphyr]

Well we keep coming back to this one. GI flickering in animations, particularly visible in cloud formations. Its such a shame when we can produce such excellent cloud structures that animating them seems next to impossible without GI flicker. Reading through past posts about this I come up with two main answers, firsty to up the GI blur radius along with the GI detail and secondly to disable GI altogether and use Fill Lights (Oshyan has a set up). The trouble is both these techniques seem to increase render times.
So my question is has anyone successfully made a GI flicker free animation including cloud formations, god rays etc using either of the above techniques.
Thanks in advance
Richard

[Oshyan]

Turning off GI and using fill lights shouldn't increase rendering time unless you use soft shadows on all lights...

- Oshyan

[cyphyr]

I've followed your advice of using fill lights but the results are not very good. Any suggestions gratefully received.
Thanks
Richard
The second one is the fill lights one

[RArcher]

To match the first frame I would simply try changing the colour of the fill lights to a more yellow colour.  If you were using the fill light clip that was posted here a couple years back, I believe that it has a fairly blue colour to begin with.

Also since it looks as though you have a lot of motion blur going on, what value did you set the GI blur radius to with your tests with GI on?  Since you are bluring things anyway, high values that reduce detail might not reduce the quality substantially.

[JimB]

Dump the underlight, it's destroying your clouds (IF that's what you have). See if changing the scattering colour brings back the yellow into the cloud underside?

[Kadri]

Richard ,you know this but you have not to produce the same image. Make a scene the way you you like without GI.
But it is up to you of course. I would not try to make the same image.  

Kadri.

[cyphyr]

Thanks guys, lots to figure out
I wanted to keep the same general look as in the first image but was unable to get it to work with the fill lights, at first.
The first image has a quite golden sun light but the fill light setup has blue or white lights. This caused the strange "under lighting" in the clouds. I eventually changed the fill light colour to the gold (one a little redder, one a little yellower) and this seems to have sorted the problem out.

NO MORE FLICKERS!!!

However I have had to get rid of my smallest 4 fake stones as they started flickering in the distance (Hmm a distance shader might have been better)

I'm rendering 300 exr's now and I'll post the anim when finished

cheers

Richard

[himalofa]

I agree with the origional post. This needs to be fixed. Turning off GI does nothing to fix the probblem. If your car has broken down and you use your bike it does not mean your car is fixed. For me the 2 biggest disappointments with TG2 were GI flicker and the black triangles. Lets hope the next release has them fixed. This is commercial software we are talking about not shareware.

[Oshyan]

Actually GI is frequently a challenge in animations. You'll find this is true in Vue, even high-end renderers like Vray. Some have partial solutions, but they're all basically compromises of some kind. Turning off GI is not ideal, but GI-like lighting can be simulated reasonably well with a good fill light setup. It's just that GI makes it easier to achieve good results. Remember that the vast majority of movie effects still don't use GI, so it's clearly not a necessity...

- Oshyan

[cyphyr]

Upon reflection and after discovering that the fill light setup is no slower than GI I'm actually not that bothered. I've got a completely working solution now and actually a lot more control over the lighting using fill lights than just GI. I may have a go later (once the anim is done) with more fill lights, see where the cutoff point is where it dose start slowing down the render.
Richard

[JimB]

Actually GI is frequently a challenge in animations. You'll find this is true in Vue, even high-end renderers like Vray. Some have partial solutions, but they're all basically compromises of some kind. Turning off GI is not ideal, but GI-like lighting can be simulated reasonably well with a good fill light setup. It's just that GI makes it easier to achieve good results. Remember that the vast majority of movie effects still don't use GI, so it's clearly not a necessity...

- Oshyan

The best way seems to be to cache the sampling which is part of a pre-pass (same as what TG2 does), which in other apps can be saved as a file. When specified as the option to use, each frame then uses that file over all the frames rather than creating a new sample per frame. Not great for dynamically changing surfaces, though, but ideal for non-deforming objects. Not sure how it'd work with TG2's surfaces, though, nor with the way clouds are rendered.

It is a big issue at times. GI knocks the stuffing out of fill lights for quality. Upping the GI Blur just muddies the image and nice detail is completely lost. Is there no way to bake the GI sampling into hard surfaces at least?

[Insquall]

(Final solution hint to devs: better optimised raytracing please  )

[Oshyan]

Certainly GI baking and/or caching are technically feasible. There are some unique challenges doing it in a large outdoor, potentially huge scale environment of course (vs. the typical more limited indoor case for most other renderers that do this well). It's something we'd like to do, but it takes time...

- Oshyan

[Henry Blewer]

Considering the large scale that Terragen 2 uses, these caches would be very huge files (probably). Be prepared, Blender water sims can take over 1 gigabyte per frame.

[JimB]

Certainly GI baking and/or caching are technically feasible. There are some unique challenges doing it in a large outdoor, potentially huge scale environment of course (vs. the typical more limited indoor case for most other renderers that do this well). It's something we'd like to do, but it takes time...

I wouldn't be surprised if it's not as bad as you think it could be. GI caches can also be additive to each other, so you could do a pre-pass for frame 0001, then move onto frame 0100 and get a pre-pass for that frame which automatically appends to the same file, or even just move the camera and create an appended pass.

Sometimes my GI pre-passes have been longer than the actual render, so it's not actually a waste in my view.