Guide to multi-pass?

Actually I'm looking for a manual, though I don't think one exists.

So... I'm looking for a description of what the different multi-pass rendering options do.

Specifically, when I'm rendering with Alpha Channel, white parts of the objects are becoming transparent... not sure if any of the multi-pass options will basically just remove the "actual" background without erasing parts of the objects.

Thanks!

Andrew

Comments

  • MystarraMystarra Posts: 30,284
    edited August 2016

    thought you meant a different multipass smiley

     

    Post edited by Mystarra on
  • DesertDudeDesertDude Posts: 652
    Turner said:

    Actually I'm looking for a manual, though I don't think one exists.

    So... I'm looking for a description of what the different multi-pass rendering options do.

    Specifically, when I'm rendering with Alpha Channel, white parts of the objects are becoming transparent... not sure if any of the multi-pass options will basically just remove the "actual" background without erasing parts of the objects.

    Thanks!

    Andrew

    Great informative thread with examples of all passes and potential uses here: http://www.daz3d.com/forums/discussion/54406/compositing-and-post-work-what-is-it-and-why-should-i-care/p1

    As for your Alpha Chanel question, we might need a little more info/screen shots to see exactly what is happening.

  • 3DAGE3DAGE Posts: 3,298

    HI Andrew

    when I'm rendering with Alpha Channel, white parts of the objects are becoming transparent...

     need some more info,.

    can you post a screen capture of your scene, and the final render. or more info about what the objects are,.

    Having parts of objects, showing transparency could be an issue with your shaders,. but i'm guessing at what you're doing,.

    Some image editors can display Alpha channel as White,. or Black, or checkered, depending on your settings in that program.

     

    You don't need to use Multi pass rendering to get an image with alpha,.

    As a quick test ,.. Add a simple object, such as a sphere, to a new, empty scene,.

    in Carrara's rendering Output options,.

    Select an image format which supports alpha channel, (PSD, PNG, TGA, TIFF

    Enable,.  Render Alpha Channel

    hit render,.

    Open your image in your image editor.

    Wherever your scene background is "empty",. you'll get alpha transparency in the image.

     

    In simple terms,. Multipass rendering creates a set of different images (passes) ...as well as a complete rendered image.(beauty pass)

    Each pass layer,. contains different information about your scene,.

    for example: Diffuse colour,.  Shadows,. specular highlights, reflections, etc. 

    these separate layers can be combined and adjusted with other image layers to produce a final composite image

    for example:  integrating fog, or other images or effects into your image. you would render a "depth pass" to create an image which represents the depth in your scene, in grey scale values.

    since you're splitting your image into separate layers of information,. there is more control and flexibility to adjust the image, lighting, colours, in 2D post production.

     

    Render passes create either a Black/White / Grey scale, or colour images, which can be used in various ways in a 2D image/video editor, to enhance, adjust, or add effects to the image

    In an image editor, such as Photoshop, PSP, or Gimp, you create a composite final image by combining different image Layers, and using (B/W or Greyscale) Mask layers, and layer Blending modes, to show, hide or adjust the underlying layers.

    In a video editor / compositor, the same principles apply.

    I hope that makes some sense

    alpha.jpg
    354 x 1354 - 100K
  • TurnerTurner Posts: 90

    Hi all - thanks - 

    Here is a shot showing render and photoshop with a red background added to illustrate where the image is becoming transparent.

     

    rendering-transparency-alpha.jpg
    864 x 296 - 49K
  • DesertDudeDesertDude Posts: 652

    Are the white parts that are going transparent, are they made of actual geometry or is it a texture map? Are you able to show a screen grab of the shader for those parts turning transparent?

  • DartanbeckDartanbeck Posts: 14,602
    Turner said:

    Actually I'm looking for a manual, though I don't think one exists.

    Not sure if you're looking for an actual Carrara manual, but if so, it's in Help > Online Help, which should bring up the first link below, but here it is for your pdf pleasure, in case you need it. If you haven't checked it out yet, you should. I don't recall if it helps with this particular situation, but it's an excellent manual. Then there's a link to the beta of a version 8 manual that a few die-hards were working on under the direction of a really cool Daz manager.

    Carrara 7 User Guide Revision G - 11 December 2008

    Carrara 8 Basic User Guide beta 0.2 - 17 June 2010 Great resources for learning the vast features and abilities that you have with this software. Although many things about Carrara are easy to learn at their very basic level, right from the interface, it helps to explore deeper by seeing what the manuals have to say. Very well written, you could be amazed at what you've been missing out on all these years!

  • TurnerTurner Posts: 90

    Are the white parts that are going transparent, are they made of actual geometry or is it a texture map? Are you able to show a screen grab of the shader for those parts turning transparent?

    In the right part of the image, the background is red - it was added in Photoshop, and as you can see, it's bleeding through transparent parts of the image. 

    Those transparent parts are simply a transparent shader, applied to geometry (lenses) that is solid; in any case, there are other parts "underneath" the lenses that are also solid... it should not be showing through here...

  • TurnerTurner Posts: 90
    Turner said:

    Actually I'm looking for a manual, though I don't think one exists.

    Not sure if you're looking for an actual Carrara manual, but if so, it's in Help > Online Help, which should bring up the first link below, but here it is for your pdf pleasure, in case you need it. If you haven't checked it out yet, you should. I don't recall if it helps with this particular situation, but it's an excellent manual. Then there's a link to the beta of a version 8 manual that a few die-hards were working on under the direction of a really cool Daz manager.

    Carrara 7 User Guide Revision G - 11 December 2008

    Carrara 8 Basic User Guide beta 0.2 - 17 June 2010 Great resources for learning the vast features and abilities that you have with this software. Although many things about Carrara are easy to learn at their very basic level, right from the interface, it helps to explore deeper by seeing what the manuals have to say. Very well written, you could be amazed at what you've been missing out on all these years!

    Thanks! I will take a look. Shame that DAZ hasn't kept up with it.

  • DartanbeckDartanbeck Posts: 14,602
    Turner said:

    Are the white parts that are going transparent, are they made of actual geometry or is it a texture map? Are you able to show a screen grab of the shader for those parts turning transparent?

    In the right part of the image, the background is red - it was added in Photoshop, and as you can see, it's bleeding through transparent parts of the image. 

    Those transparent parts are simply a transparent shader, applied to geometry (lenses) that is solid; in any case, there are other parts "underneath" the lenses that are also solid... it should not be showing through here...

    Try making sure that the underlying solid (non-transparent) material doesn't end up being black underneath - shader vs shadows, etc., which might just trick the alpha conversion into being transparent. Black = 0.00

    Still strange, though. 

    If you're looking for a possible work-around until you figure out why this is happening, try using a multipass element, like depth for example, to get a mask to use with it.

  • or you could use select with contiguous ticked before you fill with red.  make the tolerence 1 :)

     

    however, logic says that the 'solid;' back of the phone is either transparent or not rendering

     

  • Cris PalominoCris Palomino Posts: 5,367
    MistyMist said:

    thought you meant a different multipass smiley

     

    That's a "moolti" pass! :)

  • DartanbeckDartanbeck Posts: 14,602
    MistyMist said:

    thought you meant a different multipass smiley

     

    That's a "moolti" pass! :)

    Yes... she knows it's a multi-pass! lol

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