filledPolygonRGBA

filledPolygonRGBA is a routine used in computer graphics APIs to render a solid polygon with full color and transparency control. It belongs to several low‑level drawing libraries that expose a simple interface for drawing 2‑D shapes using ANSI C or C++ wrappers. The function typically accepts a list of vertices that define the polygon, the number of vertices, and an RGBA color value (red, green, blue, alpha) that specifies the fill color. Some implementations also allow the RGBA value to be supplied for each vertex so that gradients or per‑vertex transparency can be achieved. The routine internally performs polygon triangulation and sends the resulting triangles to the graphics pipeline, ensuring that the shape is rendered efficiently and correctly according to the current viewport and clipping state.

In most API documentation the call signature appears as follows: filledPolygonRGBA(float points, int pointCount, unsigned char r, unsigned char g, unsigned char b, unsigned char a). The points array holds alternating x and y coordinates. The function returns void and writes directly into the current framebuffer. It respects the graphics context’s current transform matrix, so the polygon can be positioned, scaled or rotated without modifying the vertex data.

Across libraries the name may vary slightly, e.g., drawPolygonRGBA, nvgPolygonRGBA, or sgxFilledPolygonRGBA, but the core behavior remains the same: it fills a polygon with a solid color that includes an alpha channel for blending. Because the alpha value participates in standard alpha compositing, this function is commonly used for overlay effects, UI elements, and complex 2‑D drawing tasks. The routine is efficient on both CPU‑bound and GPU‑bound rendering pipelines, making it suitable for real‑time applications such as games, visualizations, and user interfaces.