Occlusion shadows

[detbear]

Hey Everyone.

 

Wasn't sure where to ask/ re-visit this topic. Here goes.

 

Getting the shadows separated for a composite is doable and I have been creating these in a separate pass with alpha buffer for some time.

 

HOW do I get the occlusion shadows separated out or together with the normal light shadows. Can you do this for overlaying it in a compositing app??

 

I have tried numerous things, but so far no real success.

[photoman]

Hey Everyone.

 

Wasn't sure where to ask/ re-visit this topic. Here goes.

 

Getting the shadows separated for a composite is doable and I have been creating these in a separate pass with alpha buffer for some time.

 

HOW do I get the occlusion shadows separated out or together with the normal light shadows. Can you do this for overlaying it in a compositing app??

 

I have tried numerous things, but so far no real success.

 

Render to OpenEXR, there is an occlusion buffer that gets put in there.

 

Photoman

[detbear]

Hey Photoman,

 

Thanks for your reply..

 

What is the process to convert that occlusion buffer to a useable alpha overlay in a compositing App?? I use TGAs for my current project. So I need just the occlusion layer with an alpha chanel to overlay it onto the composite. Any way to acheive that via the A:M composite.....and or some other fashion.... I was able to use EXR to open the occlusion(and other channels) in a test frame. But I don't know how to convert just the occlusion buffer into an image with alpha to overlay in the existing composite.

[photoman]

It is possible with a:m composite... Let me see... I see if I can whip up a tut tonight...

 

Photoman

[robcat2075]

Hey Photoman,

 

Thanks for your reply..

 

What is the process to convert that occlusion buffer to a useable alpha overlay in a compositing App?? I use TGAs for my current project. So I need just the occlusion layer with an alpha chanel to overlay it onto the composite. Any way to acheive that via the A:M composite.....and or some other fashion.... I was able to use EXR to open the occlusion(and other channels) in a test frame. But I don't know how to convert just the occlusion buffer into an image with alpha to overlay in the existing composite.

 

Would >save as animation work? CHoose targa as the new format. EXR is treated like an image sequence.

 

Use the Composite controls to turn off all the other buffers and then resave what's left to a new targa sequence.

[detbear]

Robert,

 

Will that result overlay just the shadows into an existing composit?? Or do you have to build some kind of alpha buffer??

[detbear]

I saved just the occlusion layer out as a TGA. But It covers the underlying composite image.. There's no alpha transparency in the TGA image that separates just the occlusion shadows. So when you place it over the composite(color image)....it just covers it up.

[NancyGormezano]

Not sure I totally understand what you are wanting (not sure why you want to separate occlusion) - but if your occlusion render contains only values/shades of gray (ie you did a white render of your scene) and you also have a color layer, would using "multiply" in your composite program (AE?) work for you ? In my example I only did a flat shaded color render and an occlusion render(100%AI, AO), did not have lights, shadows - but those could be composited as well.

[detbear]

The hang-up has been as follows......

 

It's a ground plane issue really.......The ground plane/background in the final composite is different from the A:M scene...... So I'm attempting to capture just the objects and their occlusion shadows to overlay onto a different ground plane in final composite. I can get the normal shadows in a shadow pass, But I haven't been able to get both normal shadows and occlusion shadows in an alpha state to overlay onto a different groundplane.

 

Does that make any sense...I'm sorry that my explanation isn't very good...

 

Nancy....In your example above could you take those nice occlusion shadows and the sphere and place them onto a separate groundplane that was not involved in the render??? That's probably the correct question I'm trying to figure out....I don't know how to get a render of the shadows to go onto a groundplane that is not involved in the render.

[NancyGormezano]

The hang-up has been as follows......

 

It's a ground plane issue really.......The ground plane/background in the final composite is different from the A:M scene...... So I'm attempting to capture just the objects and their occlusion shadows to overlay onto a different ground plane in final composite. I can get the normal shadows in a shadow pass, But I haven't been able to get both normal shadows and occlusion shadows in an alpha state to overlay onto a different groundplane.

 

Does that make any sense...I'm sorry that my explanation isn't very good...

 

Nancy....In your example above could you take those nice occlusion shadows and the sphere and place them onto a separate groundplane that was not involved in the render??? That's probably the correct question I'm trying to figure out....I don't know how to get a render of the shadows to go onto a groundplane that is not involved in the render.

 

I would render the objects (with no background) with alpha buffer - then in AE I would composite the objects & desired background - then in AE I would set the occlusion pass render to multiply on the composite of the objects and desired background. (In my example that I did in PS - the globe is roughly selected and I sloppily cleared it's background - which accounts for rough edges - it would have been cleaner if I had done a flat shaded alpha buffer render in A:M with just the globe)

Edited March 29, 2010 by NancyGormezano

[detbear]

In the character render in A:M would you do this flat shaded or with shadows and occlussion also........?

[NancyGormezano]

In the character render in A:M would you do this flat shaded or with shadows and occlussion also........?

 

I would do the char render flat shaded probably. This can be done with setting AI=100 with no lights on. This will have No occlusion & No shadows. I thought you were doing a shadow pass as well as an occlusion render ?

[robcat2075]

BTW, EXR also has a "flat" color buffer. I think it's "diffuse"

 

 

Robert,

 

Will that result overlay just the shadows into an existing composit?? Or do you have to build some kind of alpha buffer??

 

An occlusion pass looks like a classic "White render". Much as Nancy hash shown.

[NancyGormezano]

On second thought, char flat render pass with AI=100, may not be what you want, need - you probably want to render with lights on, no shadows, AI=0 to get self shadowing, specularity, other surface properties on the models - unless rendering to exr does that for you.

 

I've never used exr nor light buffers - so that may be what you want instead - I would have to experiment (don't think I have anything that works with exr - ps 6, AE 4.1)

[robcat2075]

I've never used exr nor light buffers - so that may be what you want instead - I would have to experiment (don't think I have anything that works with exr - ps 6, AE 4.1)

 

On the OpenEXR.org website there's a PS plugin for EXR. It converts the image to 16 bits which is better than 8 but less than what EXR can do.

[John Bigboote]

Nancy hash

 

Did...I miss the wedding?

[NancyGormezano]

On the OpenEXR.org website there's a PS plugin for EXR. It converts the image to 16 bits which is better than 8 but less than what EXR can do.

 

Thanks, I got the plugin - but I don't seem to be able to do anything with the exr files from A:M in PS 6.01, other than read them - and I haven't figured out how to generate the different channels in the exr file from A:M. I suspect I wouldn't be able to use them in AE 4.1 either (haven't tried).

 

Did...I miss the wedding?

 

Coincidently, I share common ancestors with Martin, as my great grandmother's maiden name was America Hash. Martin's 5th great grandfather was my half 4th great grand uncle. That makes us half sixth cousins once removed (which makes Heath my half sixth cousin twice removed). This could account for some of my weirdness...but not all.

Edited March 31, 2010 by NancyGormezano

[robcat2075]

On the OpenEXR.org website there's a PS plugin for EXR. It converts the image to 16 bits which is better than 8 but less than what EXR can do.

 

Thanks, I got the plugin - but I don't seem to be able to do anything with the exr files from A:M in PS 6.01, other than read them - and I haven't figured out how to generate the different channels in the exr file from A:M. I suspect I wouldn't be able to use them in AE 4.1 either (haven't tried).

 

No, it won't separate any of the specialty buffers, although you could export those separately from an A:M Composite project to new EXR files and then open those in PS.

 

I don't know id there's any app that can paint and edit EXR files in full floating point terms.

[NancyGormezano]

hmmm...Seems like I can do most things to the exr files in AE 4.1 that I can to all files - I guess AE automatically converts to 8 bit ? - just not in PS, would have to change it to 8 bit - In 16 bit very few operations are available (just a few filters - eg gaussian blur, sharpen, noise, high pass, etc).

 

I'm not understanding the utility of exr files - other than for more precision eventually? Where?

 

I'm also not understanding A:M light buffers and how to generate, and how to use them in some program?

 

But I also haven't fooled much with A:M composite - a bit confusing as well

[robcat2075]

I'm not understanding the utility of exr files - other than for more precision eventually? Where?

 

Lets see... you know that common formats have 8bits or 256 values per channel... red green, blue, alpha. That's not many possible values, especailly for grayscale things like a depth map.

 

But even for full color image processing it's not much. Do a severe gamma adjustment on a dark photograph to try to bring out detail in the dark...eventually you will see banding as the few values that the dark image is made up of get spread too far.

 

In a HDR format like OpenEXR that almost never happens because each R G and B pixel is given not one of 256 possible values but one of billions.

 

But why does that matter since we can tweak our CG lights to give us perfect exposures that we dont' need to adjust? Well...

 

I'm also not understanding A:M light buffers and how to generate, and how to use them in some program?

Have you watched Fuchur's intro to A:M Composite? Good starting point.

But I also haven't fooled much with A:M composite - a bit confusing as well

 

 

With separate light buffers, each light's rays on the scene is like a different channel that you can raise or lower or even change color after you render.

Need a light brighter or dimmer or gone entirely? With EXR renders you can do that and there's no need to redo a time-consuming render, just change a level in A:M composite and see the result instantly. It's quite magical. Right now A:M Composite is the only app I know of that really preserves the full precision of the EXR renders.

[HomeSlice]

I'm also not understanding A:M light buffers and how to generate, and how to use them in some program?

But I also haven't fooled much with A:M composite - a bit confusing as well

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[NancyGormezano]

After a FEW SHORT MINUTES, you will UNDERSTAND LIFE, THE UNIVERSE, AND EVERYTHING.

 

OMG - a Holmes Cooked Light Butter Tutorial? A permanent cure for the Vapors? Eternal Life?

 

Exactly what I was looking for. No more black holes for me, I can hardly contain the alpha void. I am known to stare blankly on the edge of abcesses...er...abysses...(abyssi?) exceptionally well!

 

I'm off to do me some learnin'...Thanks!