Work in Progress: Fiat 850 Special Edition 1968

[shushens]

I worked on this for a few weeks... on and off... it has been a while since I made any progress with this. I thought I would share it here and as a question.

As you can see, the final composite is not looking right. There is a very thin white outline, especially prominent around the tyres. I have no idea where it came from. I have thoroughly examined the whole comp and it is happening when I am merging those AO passes. For some reason, there is a 1 pixel gap or something. I don't know how this could happen. None of my passes are rendered un-premultiplied. I have post-multiply checked for the beauty pass and none of the other passes have alpha.

I am not very good at compositing, yet. So it would be very helpful if you guys give me some tips on how to make this comp appear more seamless.

Thank you!

[Taros]

Hi shushens,

very nice result.

Because of your problem:
Did you switched off "Premultiply with Alpha" ?
You will find the checkbox in the mental ray options, there in Framebuffer -> Color Control. You have to switch it off. It is switched on by default, but I don't know whatfor it is needed... This makes me always crazy. I don't know how to switch it off in the prefs.

Maybe this is the reason.

Be creative
Chris

[origin]

hard to tell without checking the comp

it may be:
ao passes rendered on non black background
premultiply with alpha is off in loader
your 'lightwrapping' nodes makes the alpha of car shrink
merge nodes with wrong settings
...

whats with transform nodes after each loader ? whats their purpose ?
transform node with non default settings always degrade your image quality

You may also look at excellent tutorial at gnomon, its about compositing with fusion. He uses max to render the passes but that doesnt matter

http://www.thegnomonworkshop.com/news/2 ... tim-jones/

[shushens]

The transform node is used to make the background big enough for a decent sized car. I could find a bigger image that has the resolution already, but I liked this one. I took it as a part of the challenge, to blend the car with a noisy image.

Passes are rendered with black background.
I don't see any premultiply with alpha option in loader. There is only post-multiply and it is checked.
As far as my observation goes, until the merge immediately before the AO merge block, that border was not there.
I rendered all passes with pre-multiply off in XSI, but that does not make it go away.

I think compositors also use some sort of edge softening, which I don't know how to do. But that border is not coming from lightwrapping that I am certain of.

I can upload the EXR and the passes with the comp.
Would you please take a look?

[shushens]

Here it is:

Code: Select all

http://rapidshare.com/files/264980231/Render_Pictures.rar

[Taros]

The transform node is used to make the background big enough for a decent sized car. I could find a bigger image that has the resolution already, but I liked this one. I took it as a part of the challenge, to blend the car with a noisy image.

Passes are rendered with black background.
I don't see any premultiply with alpha option in loader. There is only post-multiply and it is checked.
As far as my observation goes, until the merge immediately before the AO merge block, that border was not there.
I rendered all passes with pre-multiply off in XSI, but that does not make it go away.

I think compositors also use some sort of edge softening, which I don't know how to do. But that border is not coming from lightwrapping that I am certain of.

I can upload the EXR and the passes with the comp.
Would you please take a look?

Try this: http://www.digitalartform.com/archives/ ... g_pre.html

[shushens]

Thanks man, but it's no longer manually done in Fusion, I think. They have the 'post-multiply with alpha' feature for exactly this reason.

[origin]

Thanks man, but it's no longer manually done in Fusion, I think. They have the 'post-multiply with alpha' feature for exactly this reason.

hey I saw your flow,
and best thing you can do is to render a new ao-shadow pass for background with car invisible to camera

[shushens]

Good idea man! Thanks!

Is there a way to turn off the primary visibility of a partition of a certain pass?

[Tekano]

of course! that is what an 'override' is for

[shushens]

I know, but a partition does not a property like "primary visibility" to turn on or off. It only have "render visibility", which turns off both primary and secondary. If I turn that off, there will be no shadow at all.

The other question that bugs me is, using Photographic Exposure Control, I can control underexposure and get some light in the shadowy zones, but that won't work when I render a separate shadow pass.

What should I do in those cases?

[shushens]

Something else is wrong in here. If that border was caused by the shadow, it would also get lighter as I raise the blend. But it stays the same. Depending on what filter I choose in merge, that outline is getting thicker or thinner. Box or Linear are giving me best results. Other ones are thick as hell.

This render was taken with pre-multiply off. I did it just to see if it was due to that problem. Apparently, it wasn't.

But when I view only the car on checkerboard, that black border is not there.

This is such a pain!



Here is the comp with the beauty and the shadow pass. I did not include the background.

Code: Select all

http://www.mediafire.com/?sharekey=dd5ec129a8443c9c41446e35a78dc463e04e75f6e8ebb871

[origin]

i don't know how you render this out, but your exr is fuxed up

this one is a quick fix:
1) goto beauty main, check post-multiply by alpha
2) swithch depth from Format to 8 or 16 int

but I suggest you check your render settings, something fishy is going on here

If you goto pixel checker tool you will see that colors outside alpha are corrupted, something like -1.#IND

Something else is wrong in here. If that border was caused by the shadow, it would also get lighter as I raise the blend. But it stays the same. Depending on what filter I choose in merge, that outline is getting thicker or thinner. Box or Linear are giving me best results. Other ones are thick as hell.

This render was taken with pre-multiply off. I did it just to see if it was due to that problem. Apparently, it wasn't.

But when I view only the car on checkerboard, that black border is not there.

This is such a pain!



Here is the comp with the beauty and the shadow pass. I did not include the background.

Code: Select all

http://www.mediafire.com/?sharekey=dd5ec129a8443c9c41446e35a78dc463e04e75f6e8ebb871

[shushens]

Doing that took care of the problem. Thanks man! But I do not understand how.



Do you see anything unusual? These are pretty typical settings, I think...

[origin]

I don't know...only thing that comes to my mind is that you have some odd settings in exposure controls attached to your camera ?

[shushens]

I took a fresh render and now it looks alright. I just need to find out how to turn off the primary visibility of all those pieces of the car in one go so that AO does covers the whole area.

Any suggestions on that?

To be honest, I think using Photographic Exposure Control shader is a bad approach. Change a setting and take a render. Change something else and take another render... why? But I am being forced to use it because I do not have any good tone mapping workflow. I tried tone mapping in Photomatix Pro, and I also tried gToneMap in Fusion. The result is pretty bad. I cannot suppress overexposure and get the underlying detail. I can do it to some extent if I lower the exposure of an EXR in Photoshop, but there Exposure falls linearly all over the image, which is not what I want And that curve there is a pain in the butt. No matter how hard I try, it never looks like an ordinary photograph. Extra vibrant colours, surreal look, it's everything I don't want (it has been very popular lately though).

Can you suggest me a good tone-mapping workflow? I think it can make my ordinary looking render pretty good, actually. From what I hear, tweaking lighting or highlights in rendertime is not the pro way to work.