The mark created by the blast of the rocket launcher is shown below. The blast mark consists of a textured quadrilateral that is rendered directly on top of polygons that form the floor. It is, therefore, co-planar with the floor polygons that it covers. The developers of Quake III Arena probably solved the problem of coplanar polygons by translating the 'top' polygons (blast mark) away from the underlying polygons (the floor), by modifying the depth value. In an early SAVAGE 2000 OpenGL ICD (1.1 9.00.20), the biasing of the depth values did not produce the desired separation between the blast mark and the underlying floor. This resulted in linear artifacts, as shown below. Another example of co-planar polygons is the lens flare effect in the 'Speedway' scene of 3D WinBench 2000.
Quake III Arena (Q3DM7): linear artifacts. SAVAGE 2000 Open GL ICD 1.1 9.00.20, 320x240.
Lens flare is a phenomenon that is caused by the lens of the camera when directed at bright light. The lens flare effect is used in the 'Islands' scene (3D WinBench 2000) to convey an impression of increased brightness. In the 'Islands' scene, the two haloes of the lens flare move towards each other, eventually overlapping one another (Frames 416 and 515).
'Islands' (3D WinBench 2000): Haloes converging (Frame 416). 320x240x32.
'Islands' (3D WinBench 2000). Haloes overlap (Frame 505). 320x240.