UV2UV : the UV based texture morphing tool by Spacymen
UV2UV : the UV based texture morphing tool by Spacymen

Post-editing a texture
(iterative process)

(from a 3D scan data by Cyberware)

This tutorial will explain how to partially re-texture an object without altering the original texture on its unmodified parts.

We spent a very short time on the quality of our object and texture to focus on the principle. You should be able to obtain much better results if you spend more time on the texturing part (2D editor).

The object used for this tutorial is provided by Cyberware by permission. Originally it's a .ply file of a hi-quality mesh (over 380.000 polygons) with vertex color. For the purpose of this tutorial, it has been decimated down to about 38.000 polygons (10%) and converted into a textured .Obj file.

This tutorial requires the use of UV2UV, UV Mapper, and a 2D image editor that manages layers and masks.

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INTRO : Prepare your work

First of all rename your object to "Head_Before.obj" and its texture to "Head_Before.bmp".
Actually the texture looks like the picture on the right.

This kind of mapping is called AUV tiles (AUV for "Adaptive" or "Automatic" UV).
It's used by several software including ZBrush, Rapidform and most of the 3D packages. It has several advantages among which are :

  • No recovering of faces
  • Less distortion of texture

So you should care of trying to preserve this mapping mode all along your production pipeline.

Actual texture
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STEP 1 : Make a "Cylindrical map" out of your object using UV Mapper

 

  • Load "Head_Before.obj"

  • Change the mapping to "Cylindrical"

  • Choose 1024 as template size

  • Choose the correct axis for your cylinder (here "Y")

  • Save the object as "Head_cyl.obj"
Cylindrical template

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STEP 2 : Make a cylindrical texture using UV2UV

INPUTS SETTINGS

  • Load "Head_Before.obj" as Source .OBJ
  • Load "Head_cyl.obj" as Target .OBJ
  • Load "Head_before.bmp" as Source texture

OUTPUTS SETTINGS

  • Create "Head_cyl.bmp" as Target texture
  • Choose a bitmap size (2048x1024)

CONFIRM & RENDER : you should get something like the picture on the right


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STEP 3 : Modify the cylindrical texture using a 2D image editor

  • Modify the cylindrical texture "Head_cyl.bmp" as you wish

  • Save as "Head_cyl_retouch.bmp"

  • Make a mask of the modified parts of your texture :
    • select the places where you have made modifications
    • paint in "White"
    • inverse your selection
    • paint in "Black"

  • Save as "Head_cyl_mask.bmp"


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STEP 4 : Reverse from "Cylindrical" to initial mapping using UV2UV

INPUTS SETTINGS

  • Load "Head_cyl.obj" as Source .OBJ
  • Load "Head_Before.obj" as Target .OBJ
  • Load "Head_cyl_retouch.bmp" as Source texture

OUTPUTS SETTINGS

  • Create "Head_After.bmp" as Target texture
  • Choose a 1024x1024 bitmap size (same as initial texture)
  • Create .OBJ "Head_After.obj"
  • Create .MTL "Head_After.mtl"

CONFIRM & RENDER : you should get something like the picture on the right

Now just do exactly the same using "Head_cyl_mask.bmp" as Source texture, and "Head_after_mask.bmp" as output Target texture. Don't ask for .OBJ and .MTL creation this time.
switch between the texture and its mask

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STEP 5 : Only keep the modified texture parts using a 2d image editor

  • Load the initial AUV texture "Head_Before.bmp"

  • Load the final AUV texture "Head_After.bmp"

  • Load the final mask "Head_after_mask.bmp"

  • Copy the final AUV texture above the initial AUV texture (layer)

  • Use the final mask image as a mask for the top layer

  • Save the result as "Head_After.bmp" to replace the old one
switch between the texture before and after
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STEP 6 : Re-import and render using a 3D package

  • Load the final .OBJ "Head_After.obj" and render

  • Compare with the older version of your .OBJ :
    • Only the modified parts of the texture have been modified leading all the other faces intact.

    • Your initial AUV texture and mapping has only been altered where you have painted...
switch between the texture before and after
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Keep going :

 

We have done this process a second time but with a planar projection from side this time.

This let us modify some parts that are more accessible with this projection mode like the ear region.

We have just modified the small hairs behind the left ear and some red light noise around the neck (see picture).
We also colored the hair knot in red.

Conclusion :
We hope this little tutorial did help you. At least we hope it did convince you that UV2UV can be used in many ways that still have to be invented !

switch between the texture before and after

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