Fractal Architect using the default flam3 renderer seems to run just fine under Lion. (If you find issues, please add a comment to the blog or send an email to support@fractalarchitect.net.)

CUDA on Lion ==========

This section only applies to those with Macs having an NVidia GPU and those who have installed the NVidia CUDA drivers so they can use Fractal Architect’s flam4 GPU accelerated renderer.

Apparently the CUDA version 3.2.17 that works best with Fractal Architect does not work under Lion.  NVidia has posted a new driver update 4.0.21 that seems to work fine with Fractal Architect for Lion users .  http://developer.nvidia.com/cuda-toolkit-40

The 4.0 CUDA driver series removed a very important capability that impacts users with MacBook Pros (2008/early 2009 model). The 3.2 CUDA drivers could use both the 9400 and 9600M GPU chips at the same time. Nvidia removed this dual GPU capability in CUDA 4 and introduced a serious driver bug where they incorrectly report the GPUs available to client programs like Fractal Architect.

To keep this simple, with Fractal Architect and Macbook Pro’s having both 9400M/9600M GPUs in them (2008/early 2009 model), you may only use the flam4 CUDA renderer with the slower 9400M GPU. (You choose this by setting the Apple System Preferences -> Energy Saver -> Graphics: Better battery life). The “Higher Performance” setting will cause Fractal Architect to crash.

For all other Nvidia GPU powered Macs that are CUDA capable, there is a new Fractal Architect bug, where Fractal Architect shows a warning in the Rendering Options pane of the Fractal Architect Preferences. It is right beside the radio buttons for selecting either Flam3 external or Flam4 Internal renderer. (These are not visible unless you have a CUDA capable Nvidia GPU on your Mac AND have installed a CUDA driver.) Just click on the Flam4 option and the warning disappears and to enable the Flam4 renderer. Click on the Flam3 options to use the non GPU accelerated renderer.