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What is a Pixel Shader?

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  • Written By: Rachel Burkot
  • Edited By: Lindsay D.
  • Last Modified Date: 17 August 2016
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    2003-2016
    Conjecture Corporation
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A pixel shader is a computer graphics tool that allows for the creation of image effects such as light, texture, shape and color. Pixel shaders make images more realistic by taking away the computerized look to them. With the help of a pixel shader program, images appear multidimensional and detailed, allowing the viewer to feel like they are looking beneath the surface of the image. A pixel shader can bring an edge to a piece of paper, shine to a doorknob or pores to human skin.

Essentially, a pixel shader works by transforming an image, pixel by pixel, into another distinct image. A pixel is an individual element of a picture that contains the image’s color and brightness information. Pixel shading is a highly specialized process, as each pixel must be altered individually. Often, over one million pixels must be addressed per frame. The detail is what makes the image look so realistic.

Programs that accomplish this task compute the images pixel by pixel in a highly complex process. After the pixels are transformed, the image is transmitted to a frame buffer for display. A pixel shader involves the use of a code. Written in a computer language called High Level Shade Language (HLSL), the code uses an input value which returns the color of the pixels so the frame buffer receives the original picture.

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Many pixel shading programs let the user control the level of detail in the images. Designed for graphic designers and photographers, these programs allow users to make passes with texture and shading. Multiple passes create a more detailed image. Developers can use pixel shaders to create the personalized effects they desire.

A pixel shader is often used in digital photography, which involves editing images. The pixel shader receives a set of instructions regarding a digital image and generates an output image pixel by pixel, following the instructions. The more dimensions the image contains, the more passes the pixel shader typically uses to complete the transformation.

To handle pixel shading in digital images, computers often have a built-in graphics processing unit (GPU). A GPU is a graphics processor that allows for the speedy processing of images. GPUs are limited, however, in that they do not support high-end procedures to alter texture. The components of a GPU can only handle a limited number of instructions for pixel shading. Therefore, specialized pixel shading programs are often used.

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