GPU Rasterization: How Graphics Cards Process Images

01

Concept of GPU Rasterization

In the field of computer graphics, rasterization is a fundamental and crucial concept, but it is not difficult to understand.

Simply put, rasterization is the process of converting vector graphics into bitmap images. In 3D graphics rendering, it is responsible for transforming geometric shapes (such as triangles) in a 3D scene into pixels on a screen so that a 2D display device can present these images.

02

Principles of Implementation

When a 3D model is created, it is usually composed of multiple surfaces, which are typically polygons, with triangles being the most common form.

To display these models on a 2D screen, a series of steps is required to convert them into 2D images. This process includes transformations, projection, and clipping to comply with the physical laws of the real world—this is what is referred to as rasterization.

03

Workflow of Rasterization

1. Vertex Processing – The input 3D model undergoes various transformation operations to determine its position in screen space.
2. Primitive Assembly – Geometric shapes, such as triangles, are constructed based on vertex information.
3. Rasterization – For each geometric shape, the pixels covered by that shape are determined, and appropriate color values are computed for these pixels.
4. Fragment Processing – The final step involves further processing each pixel, including applying textures, lighting effects, and resolving visibility issues.

04

GPU Rasterization Units

With the above principles understood, the rasterization units in GPUs become easier to comprehend. These are hardware components specifically designed to perform the rasterization process.

With advancements in graphics processing technology, modern GPUs have powerful rasterization units capable of efficiently handling complex graphical data. They also support various advanced features such as anti-aliasing, depth testing, and blending modes.

05

Summary

In simple terms, the real world or a 3D model exists in three dimensions, while a user’s display is two-dimensional. To display a 3D world on a 2D screen, the 3D image must be transformed and downgraded according to real-world physical principles, including projection and clipping—this process is called rasterization. It serves as the key step connecting the 3D world with 2D displays.

The rasterization unit in a GPU is a specialized hardware component designed specifically for this task and process. These two concepts are actually quite easy to understand.

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