Shader Hardware

Pixel shaders operate on 32-bit floating-point numbers. They read from textures and write to device memory. Each pixel has its own color and attributes.

Vertex Shaders

Vertex shaders operate on per-vertex attribute information. They project three-dimensional vertex data into two-dimensional clip space. For example, the green triangle in the following example partially obscures the blue triangle. Likewise, a rear triangle shader may not execute before a front triangle shader. Typically, the pixel and vertex shaders are independent of each other, but they can communicate with each other.

Facial Expressions

It can be used to implement facial expressions. In fact, a pixel shader can be written to apply transformations to every vertex in the scene.

Pixel

A pixel can be blended with other pixels to create a realistic skin. The pixel shader can also be used to emit rendering primitives.

GPUs

Later GPUs had a unified shader model. This allows graphics cards to make better use of the processing power.

Model

Basically, this model is like a CPU, but with much more capabilities. Shaders are programmable in a specific language, such as HLSL.

Features

Some of the features of the unified shader model include support for multiple-stage execution, deferred sharing of data, and data parallelism.

Even shaders

Even shaders written in a lower-level programming language, such as OpenGL Shading Language (OGL), are supported.

The unified shader model has made it possible for graphics cards to make significant improvements in computation throughput. Typically, a modern GPU can achieve 50x to 100x performance improvement over a CPU.

CPU

Bottleneck

However, if a bottleneck occurs on the GPU front end, a thread may stall. To avoid this, developers must ensure that they are using a programmable shader API and not a fixed-function one. A geometry shader is an unusual new programmable stage in the unified shader model. It operates before primitive assembly and after vertex processing. Like pixel shaders, it runs on 32-bit floating-point numbers, but it can also process whole primitives. Using this method, developers can use a geometry shader to calculate implicit texture coordinate gradients.

Graphics programmers can now write their own programs that will run directly on the GPU, replacing the previous approach of coding in assembler.

With a unified shader model, a graphics card can now run any kind of shader. A few years after the unified shader model was introduced, Apple released the A11 GPU.

GPUs

Unlike earlier GPUs, this chip was able to order its two-groups separately, allowing it to reduce the number of unique colors in a pixel. Furthermore, it can blend each pixel's three covered samples twice. This is helpful in smoothing jagged edges.