Difference between revisions of "ValueCorrection"

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#REDIRECT [[Value_correction]]
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* [[Polycount|Main Page]] > [[Category:Primer]] > [[Category:Texturing]] > Value Correction
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= Value Correction =
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Value Correction is a method that allows you to remove problems in value variation from a source image.
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This is a common problem when trying to create tiling textures, and is often due to uneven lighting in the source image. 
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The following Photoshop Technique will help you remove value variation but retain the hue variation, which can be useful in eliminating tiling patterns and uneven lighting.
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<<BR>><<BR>><<BR>>
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Step 1: <<BR>>
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Here is a common source image, which looks ripe for usage as a texture!
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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Step 2: <<BR>>
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Using Filter -> Other -> Offset reveals that there is uneven lighting in this image, making it difficult to tile.  How unfortunate!
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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Step 3: <<BR>>
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Go to Image -> Mode -> Lab Color<<BR>>
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<<BR>>
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In your channels, notice that you now have a LIGHTNESS channel. select that channel and notice how you can see clearly how much value variation exists!
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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Step 4:<<BR>>
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Go to Filters -> Other -> High Pass and vary the amount until most of the lighting variation is gone.<<BR>>
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In addition, you can use dodge and burn in this mode to try and hand-fix value variation problems and try to get things as even as possible.
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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Step 5:<<BR>>
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Notice that much of your Value variation is now gone!
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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Step 6:<<BR>>
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Some standard clone-brushing helps you create a tiling texture like you normally would.
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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Step 7: <<BR>>
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Using Levels and Offset again shows that you have a wonderful tiling texture with very little tiling problems. <<BR>>
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As a happy side-effect, this technique also has a habit of subduing lighting information (shadows & highlights) which is great for dynamic lighting with normal maps and specular in most engines.
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{| border="1" cellpadding="2" cellspacing="0"
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|-
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|}
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<<BR>><<BR>><<BR>>
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Notes on this technique:
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This is useful for removing contrast, but some of that contrast is good to have and you may not want to remove it all. Experiment with keeping a copy of image that hasn't been equalized in this way, and masking contrast back in only where you want it.
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For instance, you could make a value-equalized version and paint it in only over the seams you are trying to remove.
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Original thread;
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http://www.polycount.com/forum/showthread.php?p=1169603#post1169603
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<<BR>>
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* [[Polycount|Main Page]] > [[Category:Primer]] > [[Category:Texturing]] > Value Correction
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Latest revision as of 12:19, 11 October 2014

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