Jump to content
Hash, Inc. Forums
jason1025

Shadow pass

Recommended Posts

I have been taking some cg spfx classes and trying to translate the info to AM. They talk about using shadow passes and composting them. I remember Yueves talking about linear work flow. I think they are related to shadow pass.

 

Can someone point me in the direction for how to create shadow passes in AM? According to my class the pass is all black and white.

 

Is there any info on how to do the linear workflow that the Y man describes with AM?

Share this post


Link to post
Share on other sites

Hey,

 

I've currently been using shadow passes all over the place in A:M..... Mostly for ground shadows....Ground plane must be set to "Receive Shadows Only" in it's options panel...... ALSO and important....USE .TGA FILES.....Then in the render settings set both the ALPHA and SHADOW buffers to "ON".... Leave the other buffers(light, etc.) at "off"......When you render set the multi passes low at maybe 2-3 passes...Then later you can soften them in a post App like After Effects... BTW.....You won't see the shadows until you go to composite so test a frame or two first... Cut all the render settings off in the render settings except the Multi-pass and shadows.

 

THIS is a simple way for ground shadows that requires some compositing know how....... FOR shadows on the characters...I have found that rendering the shadows along with the character works best in A:M....Haven't seen a fast way to render just the shadows on the character itself....

 

Cheers,

 

William

Share this post


Link to post
Share on other sites
...Haven't seen a fast way to render just the shadows on the character itself....

 

That's golden info Detbear! I wonder, in them 'big apps', when you render a shadow pass do you get the shadows that happen on your objects as well???

Share this post


Link to post
Share on other sites
Hey,

 

I've currently been using shadow passes all over the place in A:M..... Mostly for ground shadows....Ground plane must be set to "Receive Shadows Only" in it's options panel...... ALSO and important....USE .TGA FILES.....Then in the render settings set both the ALPHA and SHADOW buffers to "ON".... Leave the other buffers(light, etc.) at "off"......When you render set the multi passes low at maybe 2-3 passes...Then later you can soften them in a post App like After Effects... BTW.....You won't see the shadows until you go to composite so test a frame or two first... Cut all the render settings off in the render settings except the Multi-pass and shadows.

 

THIS is a simple way for ground shadows that requires some compositing know how....... FOR shadows on the characters...I have found that rendering the shadows along with the character works best in A:M....Haven't seen a fast way to render just the shadows on the character itself....

 

Cheers,

 

William

 

 

Thabnks for the valuable instructions.

Share this post


Link to post
Share on other sites
...Haven't seen a fast way to render just the shadows on the character itself....

 

That's golden info Detbear! I wonder, in them 'big apps', when you render a shadow pass do you get the shadows that happen on your objects as well???

 

That's the way EXR shadow buffers work. Shadows are grouped by light rather than by object. So all the shadows cast by one light are rendered in one image no matter what object they fell on. However, that means you don't get any shadows that are behind/under an object.

 

For those, use the shadow method detbear describes.

Share this post


Link to post
Share on other sites
Do you know if AM composite will work with animation?

 

Yes. It works with EXR images and EXR image sequences. You can load non-EXR images/sequences in to A:M and re "Save As" into the EXR format. EXR has different compression schemes, each with a different purpose.

 

Read about them on pg. 10 of the EXR tech ref

 

definitely read more about EXR at Open EXR.org

Share this post


Link to post
Share on other sites
You can load non-EXR images/sequences in to A:M and re "Save As" into the EXR format.

 

I dont think this useful... where should the EXR-File get the buffers from out of for example a JPG?

 

*Fuchur*

Share this post


Link to post
Share on other sites
I dont think this useful... where should the EXR-File get the buffers from out of for example a JPG?

 

You won't need to create buffers for something that doesn't have buffers.

 

But I haven't been able to get A:M Composite to work with anything but EXR files, so if I want to include some imagery in a composite project that didn't originate as an EXR (like a photo I took with my digital camera), I need to convert it into EXR first.

 

Or is there a way to get Composite to accept a JPG or TGA?

Share this post


Link to post
Share on other sites

Hey,

 

Hash is an incredibly powerful 3D software.....It is a valuable part of my pipeline for sure.

 

I think that A:M Composite does work with shadows. The tech ref I've seen deals mostly with Open EXR files. However...I think Targa's also work. For my projects, I've chosen to work in After Effects for compositing. BUT A:M composite is up to the task.

 

SHADOWS ON OBJECTS: I always render the objects/ characters with shadows on them. I normally do a separate pass for just ground shadows and then I place them under the character layer in post..(This allows me to make the shadows as soft as I need them by applying effects and also making color adjustments to them so they better fit the scenes)..Great render time saver as well :)......I place these on top of the ground/ Background layer. Sometimes I have 5 or more layers depending on how complexed the scene...

 

I heard a while back that making a good pass of an object/or characters shadows(shadows on the object itself) requires a "non-textured" version of the object as a stand-in. Not sure how all that works in A:M though.

 

William

Share this post


Link to post
Share on other sites

I think you can import animation files into A:M composite as well Jason....I would just experiment by importing a .MOV file in as an image sequence. Right click on images in the PWS and choose import image/ image sequence.

Share this post


Link to post
Share on other sites

Use the eXtractor plugin here: eXtractor

Its for Adobe After Effects, just drop it onto your EXR-sequence and it will seperate it into whatever channel/buffer/pass you want

 

Photoman

Share this post


Link to post
Share on other sites
Hey,

 

I've currently been using shadow passes all over the place in A:M..... Mostly for ground shadows....Ground plane must be set to "Receive Shadows Only" in it's options panel...... ALSO and important....USE .TGA FILES.....Then in the render settings set both the ALPHA and SHADOW buffers to "ON".... Leave the other buffers(light, etc.) at "off"......When you render set the multi passes low at maybe 2-3 passes...Then later you can soften them in a post App like After Effects... BTW.....You won't see the shadows until you go to composite so test a frame or two first... Cut all the render settings off in the render settings except the Multi-pass and shadows.

 

THIS is a simple way for ground shadows that requires some compositing know how....... FOR shadows on the characters...I have found that rendering the shadows along with the character works best in A:M....Haven't seen a fast way to render just the shadows on the character itself....

 

Cheers,

 

William

 

 

 

I cant get it to work when I fallow your instructions. I just get black screen with blank alpha that is flat with no difference. Any ideas?

Share this post


Link to post
Share on other sites

Render the first frame of this PRJ with "use settings from > The Camera".

 

This renders a black frame with the vase's shadow in the alpha buffer.

 

ShadowBufferTest.prj

Share this post


Link to post
Share on other sites

Thanks Robert. How would you create a shadow only pass for all shadows and or AO shadows in the chor with multiple objects? I want to save render time by doing to separate renders. The Pros seem to render a flat pass without shadows then render the shadows with occlusion, and then composite.

Share this post


Link to post
Share on other sites

I recall that EXR renders include a separate AO buffer, but if your compositing app doesn't handle separate EXR buffers that won't do. A:M's "build composite" can do quite a bit with EXR renders but I haven't done much with it.

 

Shadow buffers in EXR are a bit different than the TGA shadow buffer. TGA captures the whole shadow, even the part covered by the object, but only on surfaces set to "Shadow only" so I'm not sure how self shadowing is handled. An EXR shadow buffer has all the shadows cast by a light, but only the portion visible to the camera. These shadows are not convenient to blur in post like the TGA shadows are..

 

in TGAs, occlusion or Ambiant occlusion would be captured by doing an all-white render. All objects (and sky) white so that they are darkened only because of the lighting.

 

In the Birn book he talks about how it is often necessary to capture different shadows on different surfaces in separate passes. It gets complicated when a shadow is falling on something that is also casting a shadow or casting a shadow on itself.

 

You would need to analyze your scene to determine which shadows need to be captured separately from others, if at all.

Share this post


Link to post
Share on other sites

Is there an easy way to switch all models to white leaving just the shadows on a bunch of white objects? What do you think about a feature request that is a switch that globally turns all objects surface color to white?

Share this post


Link to post
Share on other sites
Is there an easy way to switch all models to white leaving just the shadows on a bunch of white objects? What do you think about a feature request that is a switch that globally turns all objects surface color to white?

 

Isnt this what the Null-Shader does?

 

*Fuchur*

Share this post


Link to post
Share on other sites

>Isnt this what the Null-Shader does?

 

*Fuchur*

 

 

 

By dragging this group up and down the grouphierachy you can switch the other groupmaterials on and off.

 

To deactivate decals too, you will have to create a pose though.

Share this post


Link to post
Share on other sites
To deactivate decals too, you will have to create a pose though.

Or you can use the Nancy method.

Set the model to Front Projection Target in the chor.

Apply a solid white rotoscope image to the camera.

I think this also turns decals white, but bump maps will still render.

Share this post


Link to post
Share on other sites
To deactivate decals too, you will have to create a pose though.

Or you can use the Nancy method.

Set the model to Front Projection Target in the chor.

Apply a solid white rotoscope image to the camera.

I think this also turns decals white, but bump maps will still render.

 

 

Thanks folks

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...