Strange sky lighting in animation

[kopperdrake]

Hi chaps...again, nto strictly archviz but it's an arch viz that it's happening in so I thought I'd post here. I have a 200 frame section of animation, and as the camera moves in to the entrance of the site the sky will 'flicker' very slightly...some frames are basically lighter than others, but only where the sky is and where the sky is reflected in the windows - everything else stays the same. The sky is actually a dome object with the surface set to 100% luminosity and is unaffected by the lights in the scene. There are 2 main sun lights and some smaller localised plant lights (about 1m diameter). No GI or lighting hacks...plain raytraced area lights.

I'm rendering it on a 4 CPU farm (small holding ;) ), but the flickering doesn't point to any one cpu missing anything. In this particular attempt the first 4 frames are darker (I've attached a pair of light/dark frames for you to see), but in past attempts they change at random as the scene plays back - but not so you can point at any one CPU. Anyone else seen this happen?

[Nigel Baker]

Hello Kopperdrake,

Are you out putting as sequence files or as a continuous animation ( i.e. QT )

[kopperdrake]

Hey Nigel :) Sequence files (tga), I never save anims unless it's for a quick and dirty preview :)

[Nigel Baker]

Hello there Kopperdrake **** them peskie kids.

Just back, Having a look at the two images within photoshop to check the difference.
Within the whole image there is a change within the Luminance of the whole image.
See the tree area on the right and the roof of the building. Probably due to the image changing intensity?

Like to know a little more about the files. But first is the evil frame the same frame all the time or is it always a different frame.

Have you increased the pld pass or used the? Are you rendering fields or frames?
Have you thought about the mipmap? You could blur the cloud texture a small amount.

Just thinking of possible ways of trying to illiminate it. Shooting in the dark.

Also have you prayed.
Keep posting.

Oh yes, is it possible to to some post production on it. It seems the easiest and quickest

[kopperdrake]

Hey :) Thanks for replying :)

If you take them into photoshop and crop the roof area you can see there isn't a change in the luminosity there - it may be a visual illusion when looking at the whole image. Pretty much everything stays the same except the sky and its reflections, so I have to assume something is up with the skydome. It has unaffected by fog turned on, but maybe that's kicking in - something to do with big objects maybe? I know big and small objects in the same scene can sometimes play havoc with the rendering engine (afaik). I'll have to try and swap the texture out and see if it happens with another format.

I'll post here when I find out the culprit (probably user error as always ;) )

[<HD>]

You've made the skydome unaffected by the scene lights but also uncheck cast shadow, recieve shadow etc and check the skydome texturing, specularity, diffuse etc and that theres no envelope on the lum' channel. I'm also assuming the sky isn't an avi or some sort.

[kopperdrake]

Aagh! I've killed everything in the scene except the dome and the various lights (2 sun lights and several limited range plant lights), and this time it only does it on the first frame!! Only the first frame is lighter, and then the rest are darker. No envelopes, no lum channel (it's at a fixed 100% lum)...I'm really hitting my head against a wall! It's a big texture - tomorrow I'll try with a smaller texture. Oh, and it was a tif before, bit now it's a tga - 24bit.

[Nigel Baker]

Hey Kpooerdrake,

Is it possible to move the whole test animation ONE frame on and see if the new frame 2 which was originally frame 1 has the artifect in it.

Fingers crossed.

[<HD>]

Your not using any kind of 'spinning light' effect for the sun for softer shadows are you? This would produce an odd first frame because the motion blur wouldn't work until the next frame.