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Vector Displacement

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  • Advanced Member

Try opening up the exr in photoshop and adjusting the exposure (add a stop or two) to make sure negative values are actually there (they're normally displayed as black since the're stored as "blacker than black"). If you saved with black (not normalized), they should be there. If not, it's a bug with 3d coat not saving negative floating point numbers in exrs and Andrew would have to address that. Alternatively, you could save as a float point tiff, open in PS and save as EXR (not sure if houdini supports float point tiffs). Again, you'll have to adjust exposure to make sure the negative values are actually being saved.

The EXR file format itself supports full dynamic range (signed float point numbers with no restrictions) so it's perfect for displacements.

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  • 5 months later...
  • Advanced Member

You can also use Houdini's viewer "Mplay" which has an Adapt Range button and easy single channel viewing, see image for quick help.

Houdini should support floating point TIFF just fine, though to be honest I usually use EXR.

Last tidbit before I sleep: When rendering in Houdini, convert your images to RAT format which is Houdini's native texture format. Houdini can use almost anything for a texture, but RAT will be fastest with least RAM used. You can use Mplay to save out an image to RAT, or the standalone tool "icp" (shell on Linux, terminal on OSX, Houdini Command thingy on Windows, sorry I don't use Windows much I forget the menu entry name).

FYI this viewer is available from the free version of Houdini (Apprentice) for Windows OSX and Linux in case people want a really nice image (and flipbook) viewer.


Peter B


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  • Applink Developer

This topic was on the top of the forum, so I decided to make one more try to fix this thing. I don't know what I did but now it seems that both positive and negative depth works.

See the picture. Psyborgue, if you are out there, maybe you can check the houdini file and see if there something to fix. I added Fit Range node just after texture node and that seems

to work nicely. I will make a small tutorial soon how to make this work in 3d-coat and houdini.



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  • 7 years later...

The main advantage of 32-bit maps is that you don’t need to enter a depth factor to producing an accurately displaced render. This means less effort for an even more accurate result.

- Displacement

This is a floating point value which is applied as a shift to the displacement amount. It defines the value of the displacement map that is considered to be zero displacement. This value can vary depending on how the displacement map has been generated.

- Vector Encoding

Floating Point Absolute (for floating point maps) or Signed Encoding (usually 8 bit maps, whose rgb is remapped to the (-1..1) range).

- Vector Space

Can be World, Object, Tangent. This is the coordinate space where the vector is applied.

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