linerendering

Line rendering is a process in computer graphics for drawing line primitives, which represent straight or polyline segments in 2D or 3D space. It is a subset of rendering focused on how lines are sampled, rasterized, shaded, and displayed, and it is essential in vector graphics, CAD, GIS, and outlines in 3D scenes.

Line rendering typically involves transforming line data from model space to screen space, performing clipping against the view frustum, and rasterizing the lines into fragments or pixels. Classic approaches include Bresenham’s integer-based rasterization and Wu’s anti-aliased line algorithm. Anti-aliasing is important for reducing stair-step artifacts; methods include MSAA, post-process techniques like FXAA, and, in some pipelines, alpha blending to produce smoother edges. In addition to single-pixel-wide lines, rendering thicker lines usually requires representing lines as textured quads or cylindrical tubes, or using shader-based geometry that creates a ribbon around the centerline.

Modern graphics APIs expose line primitives such as line lists and line strips, for example in OpenGL (GL_LINES, GL_LINE_STRIP), DirectX, and Vulkan. However, many GPUs provide limited or inconsistent support for wide or styled lines, which has led to common practice of simulating thicker or dashed lines with additional geometry or instancing. Line joins, caps, and dash patterns are additional stylistic features that affect appearance and rendering cost.

Applications of linerendering include technical drawings, road and river maps in GIS, vector illustrations, and the outlining of 3D models. Limitations often involve aliasing, depth testing with overlapping lines, and performance considerations on complex scenes.