The pixel pipeline, also known as the rendering pipeline, is a sequence of stages responsible for generating the final 2D image from a 3D scene. It begins with the 3D geometry of the scene and progresses through various stages to handle transformations, lighting, shading, and texturing before arriving at pixel-level operations.
The first stage of the pixel pipeline is vertex processing, where the 3D coordinates of objects in the scene are transformed into 2D screen coordinates. Vertex shaders are often used to manipulate vertices, applying transformations, deformations, and other effects.
Rasterization is the process of converting geometric primitives (such as triangles) into pixel fragments. Each fragment represents a portion of a primitive that corresponds to a pixel or a group of pixels on the screen.
After rasterization, pixel shading comes into play. This stage determines the final color and appearance of each pixel. Pixel shaders (or fragment shaders) calculate lighting, materials, and other surface properties, giving each pixel its unique characteristics.
Texturing involves applying 2D images (textures) onto the 3D surfaces in the scene. Texture mapping coordinates are used to position and map the textures onto objects, adding detail and realism.
The Z-buffer, also known as the depth buffer, is used to keep track of the depth or distance of objects from the camera. Depth testing is performed to determine which pixel fragments are visible and should be drawn.
The final stage involves framebuffer operations, which include blending multiple fragments to determine the pixel's color and writing it to the frame buffer. Techniques like alpha blending and antialiasing may be applied here.
Once all pixel pipeline stages are completed, the resulting image is sent to the display for viewing. This process occurs at a high speed, often resulting in real-time rendering for video games and interactive applications.