PTM's (Polynomial Texture Maps)

Overview | Light Space | Image Enhancement | Viewing a PTM | Building a PTM


Image Enhancement


Reflection and Color information may also be mathematically enhanced using tools in the PTM Viewer software. Enhancement reveals surface features that are faint and/or indiscernible in the original digital photographs.

SPECULAR

In 3d lighting models, reflection is called 'Specular'. In the PTM viewer, specular enhancement separates display of the reflective and color properties of illumination. When specular enhancement is enabled, the purely reflective characteristics of an object can be viewed independently of, or in combination with, the color properties. When the reflective properties are displayed alone, the PTM content appears as if it was made of a highly reflective material like chrome or opaque glass. In the 'real world', such highly reflective material discloses a high degree of information about small changes in surface features. This is illustrated by the effect of a small dent in the fender of a shiny new automobile. When the content of a PTM is displayed in this manner, the captured 3D normal information shows features not visible in even the best traditional photograph. Specular enhancement can be displayed in the applet PTM Viewer by right clicking in the image display window and selecting EFFECTS ---> SPECULAR. Here is a PTM shown on the left with no enhancement and on the right with only specular properties displayed.

 
PTM detail with out specular enhancement   PTM detail with specular enhancement

Specular enhancement permits blending of color and reflection properties. The proportion of color and reflection is set with a pair of sliders in the parameter control window that determines the amount of image illumination provided by each property. As increasing or decreasing the intensity of each slider increases or decreases the overall image brightness, the global illumination intensity controlled by the 'Light' slider at the top of the parameter control window may need to be adjusted to compensate for too much or too little brightness.

Here is a PTM shown on the left with equal proportions of reflection and color properties and on the right with one part reflection to four parts color.

 
PTM detail with equal proportions of reflection and color properties.   PTM detail with one part reflection to four parts color.


DIFFUSE GAIN

Color enhancement, called 'Diffuse Gain', increases the tone value (light/dark) contrast in the image. As the illumination direction changes, Diffuse Gain increases the intensity of highlights and shadows to disclose surface features. Diffuse Gain can be displayed in the applet PTM Viewer by right clicking in the image display window and selecting EFFECTS ---> Diffuse Gain

 
PTM with out diffuse gain.   PTM with diffuse gain.






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Related CHI Content:
PTM Examples
Reflection Transformation Imaging and Virtual Representations of Coins from the Hospice of the Grand St. Bernard (424 KB pdf paper download)

Related Web Resources:
PTM's
   




















 
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