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Thread: PS Glass Distort filter for Gimp?

  1. #1
    Community Leader Gidde's Avatar
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    Question PS Glass Distort filter for Gimp?

    (the Distort - Glass filter on the river gives it away but I don't know if GIMP has something similar or not)
    It does not, much to my dismay. I've been experimenting for days trying to find something in GIMP that will even approximately reproduce the effect.

  2. #2
    Administrator RobA's Avatar
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    Quote Originally Posted by Gidde View Post
    It does not, much to my dismay. I've been experimenting for days trying to find something in GIMP that will even approximately reproduce the effect.
    I have this in my notes from way back....

    * Duplicate your layer, run a Sobel edge-detect on the duplicate, and then add a touch of Gaussian blur.
    * Create a new white layer (Xoffset) and Bump Map it against the duplicate with darkness compensation disabled, an Azimuth of "0", and an elevation of about "30".
    * Create a new white layer (Yoffset) and do a Bump Map against the duplicate with darkness compensation disabled, an Azimuth of "270", and an elevation of about "30".
    * Perform a Displacement Map on the original layer, using the Xoffset and Yoffset layers as the corresponding displacement maps and adjusting the amount of displace to suit.

    Can someone with PS and Gimp compare, and if it works I can script it up, OK?

    -Rob A>

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    Community Leader Gidde's Avatar
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    Hmm. I just tried this, and with a noisy ocean layer the sobel edge-detect gives me a completely transparent layer; dead in the water. Then I tried it with a black and white land-mask type image, and got very little distortion (even with displace values > 100). It looks like the distortion it does give is on the right track though. Could be that it needs something more defined than solid-noise colored clouds (with light coastal area - same as I started with for my glass-ified ocean in my last map) and less defined than black/white stark image. I'll keep playing with it.

    // Edit: Here are some comparison images in case they help. The blue image is just original and photoshop versions. The B/W is following the instructions you gave with a 200 displace.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by Gidde; 07-14-2010 at 12:16 AM. Reason: Added Samples

  4. #4
    Administrator RobA's Avatar
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    Quote Originally Posted by Gidde View Post
    Hmm. I just tried this, and with a noisy ocean layer the sobel edge-detect gives me a completely transparent layer; dead in the water. Then I tried it with a black and white land-mask type image, and got very little distortion (even with displace values > 100). It looks like the distortion it does give is on the right track though. Could be that it needs something more defined than solid-noise colored clouds (with light coastal area - same as I started with for my glass-ified ocean in my last map) and less defined than black/white stark image. I'll keep playing with it.

    // Edit: Here are some comparison images in case they help. The blue image is just original and photoshop versions. The B/W is following the instructions you gave with a 200 displace.
    Playing a bit more.

    I tried Filter->Edge Detect->Edge (Sobel, value 10) (Not Filter-->Edge Detect->Sobel)
    Gaussian blur 5
    Duplicate the blurred layer.
    Filter->Distort->Emboss (emboss, 0,30,30) on one (used as X displacement)
    Filter->Distort->Emboss (emboss, 270,30,30) on the other (used as Y displacement)
    Filter->Map->Dispace (20,20, edges smear)

    The blur changes the size of the ripples and the displace amount controls the sharpness?

    Here is the result:
    Click image for larger version. 

Name:	ripple.jpg 
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ID:	26987


    -Rob A>

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  6. #6
    Community Leader Gracious Donor Jaxilon's Avatar
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    Look great RobA.
    “When it’s over and you look in the mirror, did you do the best that you were capable of? If so, the score does not matter. But if you find that you did your best you were capable of, you will find it to your liking.” -John Wooden

    * Rivengard * My Finished Maps * My Challenge Maps * My deviantArt

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    Guild Journeyer hohum's Avatar
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    Default Glass Filter (sorry about the hijack)

    Here is what I got:

    Click image for larger version. 

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    You need to run Filters>Edge Detect>Edge with a sobel setting. Then the displacement map with setting of 50 for both. If you do Filters>Edge Detect>Sobel you get a transparent layer.

    This is with lighting effects with a Yoffset layer bump mapped.
    Click image for larger version. 

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    And then the two combined with the light effects layer at 25% opacity.
    Click image for larger version. 

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    Not perfect, but perhaps on the right track. I had tried a beaten metal effect with felimage galvanized noise and lighting effects that also did something similar.

  8. #8
    Administrator RobA's Avatar
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    It looks like sobel of the source is just an option (ripples will be harsher where there are larger transitions, and the ripples parallel the transients).

    Here is the same, but starting with a high turbulence plasma cloud that was blurred 3px sobel edge detected, plurred 3 px again, then the rest of the steps followed (displace of 10 in the last step):

    Click image for larger version. 

Name:	ripples2.jpg 
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ID:	26993

    -Rob A>

  9. #9
    Guild Journeyer hohum's Avatar
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    I'm just stealing you guys's stuff to see it side by side.

    Gidde's: RobA's:
    Click image for larger version. 

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ID:	26995 Click image for larger version. 

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    Pretty darn close. Perhaps just a little more blur to the final image and they would be identical.

  10. #10
    Community Leader Gidde's Avatar
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    Good call on the move! We had totally hijacked that poor thread

    Quote Originally Posted by RobA View Post
    I tried Filter->Edge Detect->Edge (Sobel, value 10) (Not Filter-->Edge Detect->Sobel)
    Aha! That was my problem.

    Thanks for helping test this out, Hohum, your test looks absolutely fantastic. In fact, the difference between yours and mine looks almost exactly like the differences if you play with the settings in the PS filter.

    I can't wait to try this on my current WIP. Rob, you are, as ever, my hero.

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