immediatemode

Immediatemode is a graphics rendering approach in which drawing commands are executed and displayed immediately as they are issued, rather than being stored and organized in a reusable scene representation. In an immediatemode system, applications issue primitive drawing calls (such as vertices, lines, and triangles) that are sent to the GPU on the fly, with little or no persistence of the geometry data between frames.

Characteristics include immediate execution of commands and little or no persistence of geometry data between frames. The approach offers simplicity and rapid feedback, making it attractive for small, dynamic scenes, debugging, or learning graphics concepts.

Limitations include high CPU overhead, poor data reuse, and difficulty scaling to complex scenes. Because geometry is reissued each frame, there is little opportunity to batch work or exploit GPU-side storage and caching. This makes immediatemode less efficient on modern hardware.

Historically, immediatemode was common in older graphics APIs. In OpenGL, immediate mode used glBegin, glVertex, and glEnd to issue individual primitives; this style was deprecated in modern core profiles. Modern OpenGL and Vulkan rely on vertex buffers and command buffers to batch and reuse geometry.

Alternatives include retained-mode techniques, scene graphs, display lists in legacy contexts, and, in modern APIs, vertex buffer objects (VBOs), vertex array objects (VAOs), and shader-based pipelines. Immediatemode is generally avoided for real-time rendering but may still be used for simple demos or instructional purposes.