Re: Using Normal Map as a Displacement Map

[Luke <luke(at)rsp.com.au>]

OK,

Lemme try a stab at something based on intuition....

For each shading point take the normal:
N = << x, y, z >>

Then the lookup at the normal map at this point:
( I am assuming this is normalized in the map to be length( M ) = 1, where r, g, b -> [ 0, 1 ] )
M = << r, g, b >>

and then calculate:
dotProduct = N.M ( dot product )

then take the result as ( approximately ):
( for a maximum displacement height of mag units, with a height offset of offset units )
displacementHeight = ( mag * dotProduct ) + offset

This is a really big approximation but it seems reasonable - although haven't tried it myself....
Without integrating the image, this would give you a numerical first order approximation to the correct result.

Even if it doesn't work for you I hope it helps get the brain juices flowing....

L.

Oscar Juárez wrote:

http://66.70.170.53/Ryan/heightmap/heightmap.html

this tool will create a displacement map from a normal map... i think the resolution is not very good
but it might help you out, havent tested it myself quite well...

hope it helps

Oscar


Gene Crucean wrote:

Hmm... I wonder if you could use a multi direction displacement shader to get something working? Like the waterblue shader.

I haven't found a use for that shader yet but I might have to experiment with that a little.




On 10/4/05, *Raffaele Fragapane* <jaco(at)thejaco.com <mailto:jaco(at)thejaco.com>> wrote:

    generating a normals map from an elevation map (like bump or
    displacement) is trivial, as all you need to do is to recalculate the
    normals based on the elevation at the texel.

    I could be wrong about this, but I believe the other way around
    however
    is A LOT harder, as you'd have to, in simple words, to keep trying
    different solutions until you can figure out what elevations would
    re-orient the normals so that it matches the normals map.
    Unless there's some algorithmic solution in some siggy paper I
    ignore,
    is seems one of those situations where you deal with an integration
    problem (and eventually even worse, a minimization one) of
    undefined order.

    ******************************
    |     Raffaele Fragapane       |
    |     Rising Sun Pictures      |
    | "Remember, TD is for TopDog" |
    ******************************



    Brinkley, Marc wrote:

    > Yeah that's the problem, all I have is the normal map and nothing
    > else. All I really need is to displace an object with a normal
    map to
    > create the depth/displacement map.
    > Sorta the opposite of using a displacement map to generate the
    normal
    > map, which BTW works nicely with Ultimapper. Almost like I need to
    > have Ultimapper obey Bump Map or something like that.
    > Thanks
    >
    > Marc Brinkley - EA | Chicago
    > mbrinkley [at] ea.com <http://ea.com>
    > 847.884.2000 x118
    > "Error: The operation completed successfully"
    >
    >
    >        ------------------------------------------------------------------------
    >     *From:* owner-xsi(at)Softimage.COM
    <mailto:owner-xsi(at)Softimage.COM> [mailto: owner-xsi(at)Softimage.COM
    <mailto:owner-xsi(at)Softimage.COM>]
    >     *On Behalf Of *Per Edwards
    >     *Sent:* Tuesday, October 04, 2005 8:34 PM
    >     *To:* XSI(at)Softimage.COM <mailto:XSI(at)Softimage.COM>
    >     *Subject:* Re: Using Normal Map as a Displacement Map
    >
    >         Hey all,
    >
    >         Here's one that I am bumping my head against.
    >
    >         v5 BTW
    >
    >         I have a normal map that is piped into the new XSINormalMap
    >         node in the rendertree. The XSINormalMap node is hooked into
    >         the Bump Map on the material. Renders just fine..actually,
    >         really nice.
    >
    >         I would like to be able to use the Normal Map as
    displacement
    >         instead of bump. Any thoughts? I don't use the RT that
    much so
    >         shading trickery is not my gig.
    >
    >         I am really trying to find a way to convert a normal map
    into
    >         a displacement map and I was hoping to use the XSINormalMap
    >         node and some RenderMap/Ultimate magic to pull it off. But I
    >         am not getting what I want…or at least I am not seeing a way
    >         as Ultimap does not obey bump map.
    >
    >         Eh?
    >
    >
    >     Normal map data is stored as normals, i.e. It has no length
    value.
    >     In theory you could walk the map and calculate a heightmap from
    >     that, but it would be a hell of a lot slower than using a
    correct
    >     dispalcement map to start out with. Whatever you used to
    generate
    >     your normal map should be able to generate a displacement
    map for
    >     you at the same time.
    >
    >     per
    >
    >------------------------------------------------------------------------
    >
    >No virus found in this incoming message.
    >Checked by AVG Anti-Virus.
    >Version: 7.0.344 / Virus Database: 267.11.10 /119 - Release Date:
    10/4/2005
    >
    >

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-- 
luke emrose
technical director - luke.emrose(at)rsp.com.au
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