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Thread: objects as a mask

  1. #1
    Animator/Compositor wibly wobly's Avatar
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    objects as a mask

    I'm trying to wrap my head around a way to do this and I haven't been able to find a way, and I'm drawing a black searching. Basically, what I'm trying to do is use an object and it's position to generate a clip map. I don't want to use a texture as a clip map because it will run straight through on a Y axis, I want to punch a whole in a a background object where the foreground object obscures it (without seeing the FG object). To further elaborate, I have a shallow boat and you can see the generated water in the bottom because of it's open design. I want to use a simple wireframe mesh that sits at a higher plane in the boat and wherever you see that FG object, it will cut a hole on the water. Otherwise, if I use a textured clip map, it's too wide because boats are wider higher at the top then at the bottom.

    Cheers.

  2. #2
    You could use an object that's set to be a Matte object in the object properties.
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  3. #3
    Animator/Compositor wibly wobly's Avatar
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    I'd rather not just use the clip map setting under the object/render settings to create the whole as I'd have to render out multiple passes (I'm assuming this is what you're referring to). I'd like to track the item info of the object through a node tree to create it so I don't have to worry about rendering more layers. I just haven't been able to figure out how. I'm sure the nodes are there to make this but, I haven't been able to figure out how to make an item cut a whole in another.

  4. #4
    I don't think Ernpchan understood your question, matte objects are used for making compositing passes. In this case compositing is a good idea, but a simpler solution can be made if you save out two diffrent versions of your scene, one with everything (including the boat if you want it to reflect on the water), and the other just the boat. Render both sequences, the boat sequence with alpha, layer the boat pass on top of the water pass and you are done.
    Last edited by Danner; 01-21-2014 at 09:01 AM.

  5. #5
    Axes grinder- Dongle #99
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    Cool

    Riiiiiiiiiiiiiight (pounding head w/fists)... I did this YEARS ago. --Now, how did I do that?

    IIRC, I used SURFACE EFFECTORS. I don't think we even have them any more.

    Well, here's one way:
    1. make a poly that's the cross section of the hull at the altitude you want the boat to be in the water (in "drill speak", the 'core' of the water and hull)
    2. render out a mask of that poly head on (90*)
    3. trim the mask image to have minimal borders
    4. load the mask
    5. parent a NULL to the boat
    6. assign the image as a clip map to the water
    7. use the NULL as the image's REFERENCE OBJECT
    8. the NULL and the IMAGE will move w/the boat,
    9. and having a null will allow you to cheat it +-X/+-Z
    They only call it 'class warfare' when we fight back.
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  6. #6
    Axes grinder- Dongle #99
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    The above will work right away (no nodes!) but if you want to explore a nodal solution I'd suggest looking into DPont's BOOLEAN node....thingy. I have no idea how it works, but IIRC it will allow you to have one object cut away another much like a clipmap, but in 3D.

    This is a superior solution for a more cartoony boat that jumps out of the water a lot.
    They only call it 'class warfare' when we fight back.
    Praise to Buddha! #resist
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  7. #7
    Animator/Compositor wibly wobly's Avatar
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    Thanks guys. Your methods you're describing are is something I'd prefer to avoid. I'm going to be rendering out object passes and layers as it is and I'd just like to avoid having to play around with yet another thing in AE. I'd like to have a totally in LW solution. I have too many other things I'd rather have to pay attention to.

    edit: The only thing I've found so far about DPont's BOOLEAN node is that it was crashing a lot of people. :/ I'll give it another look. I don't remember seeing much documentation about it.

  8. #8
    Yeah I may have jumped the gun on my response. Using the matte object route will let you cut a hole out as a whole in your render. It's not gonna work on an individual layer/object like how a track matte works in AfterEffects.
    My opinions and comments do not represent those of my employer.
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  9. #9
    Axes grinder- Dongle #99
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    ??? I'm not talking separate passes: the REFERENCE OBJECT clip map works entirely within LW.

    The clip map render is ONE image, not a pass. Once its prepped, you're done.

    0_o
    They only call it 'class warfare' when we fight back.
    Praise to Buddha! #resist
    Chard's Credo-"Documentation is PART of the Interface"
    Film the cops. Always FILM THE COPS. Use this app.

  10. #10
    Rethinking my solution, it wouldn't work if you look at the boat from a side.. i was thinking a top down view.. hmm

  11. #11
    Axes grinder- Dongle #99
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    Here's a third possible solution, dependent on the particular meshes: Model the water AROUND the boat. If the hull is sufficiently thick or the displacement of the water very slight you can move the water object THRU its displacement (i.e. World Coordinates).

    IOW, the water is parented to the boat. The hole moves w/the boat. Water displacement is World Coordinates, and exclusively on the Y axis.

    It might be convenient to add bones to the water to solve any interpenetration issues.
    They only call it 'class warfare' when we fight back.
    Praise to Buddha! #resist
    Chard's Credo-"Documentation is PART of the Interface"
    Film the cops. Always FILM THE COPS. Use this app.

  12. #12
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    Quote Originally Posted by wibly wobly View Post
    ...The only thing I've found so far about DPont's BOOLEAN node is that it was crashing a lot of people. :/..
    If it is the case, I'm very sorry
    it was not intended to crash people.

    Denis.

  13. #13
    Axes grinder- Dongle #99
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    Anytime I've supplied Denis with bug reports and appropriate supporting sample files, he has fixed the problem frighteningly fast.

    EVERY time.

    So, if people are having troubles w/any of Denis' offerings, they should create appropriate examples and explain the problem fully to him.
    They only call it 'class warfare' when we fight back.
    Praise to Buddha! #resist
    Chard's Credo-"Documentation is PART of the Interface"
    Film the cops. Always FILM THE COPS. Use this app.

  14. #14
    Animator/Compositor wibly wobly's Avatar
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    Quote Originally Posted by dpont View Post
    If it is the case, I'm very sorry
    it was not intended to crash people.

    Denis.
    Wow, I don't think I phrased exactly what I meant regarding that comment. You're nodes are a gawdsent. I don't know what I'd do without them! The only related information I found that use that node was causing the person's system to crash all the time. It's probably a very isolated problem as, like most places on the internet, we only come out and complain when we have problems. The content people, just carry on doing what they're doing.

    I'll have a second look at your boolean plugin. It sounded like it could do what I'm looking for. I just got sidetracked.

    edit @jeric Agree, his stuff is fantastic.

  15. #15
    Axes grinder- Dongle #99
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    WW, do you have a still frame of your project?
    They only call it 'class warfare' when we fight back.
    Praise to Buddha! #resist
    Chard's Credo-"Documentation is PART of the Interface"
    Film the cops. Always FILM THE COPS. Use this app.

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