Category Archives: News

Is it time to remove GPU rendering support from the app?

Let’s face it. Apple has done a terrible job producing reliable drivers for OpenCL and Metal compute shaders. Each Mac OS update brings the terror of: Did Apple kill the drivers this time?

Since March 2017, the state of OpenCL drivers for AMD GPUs has been: Unusable

Either the app crashes or you get a total system lockup with OpenCL AMD rendering. (late 2016 MacBook Pro with AMD GPU)

With about 100 different Mac configurations released in the last 6 years that have GPUs, your results will probably be very different.

For the 5 previous years, the AMD OpenCL drivers had been rock solid.

Fractal Architect is the “Rosetta Stone” for GPU compute testing. It allows you to easily switch render devices between OpenCL, Metal, and CUDA. It allows you to check their LLVM compilers for their ability to compile the extremely complex kernels used by the app.

It allows you to profile and compare performance between devices and between different Mac models.

But supporting GPU rendering is very expensive. Guess who pays for all of the test Macs?

The revenue base to support this GPU support feature is tiny.  Flame fractal apps are a micro niche. To date (since 2009) the entire revenue from the app goes toward buying test hardware and nothing else !

This year, because of driver quality problems, worldwide sales of the app are now so low that I can only buy 1 test Mac every 3 years. I cant test the app on a current generation AMD GPU on a low end MacBook Air. I can’t test next years AMD GPU on last year’s Mac.

So should:

A) GPU rendering be removed from the app as test hardware is cost prohibitive?

or B) should it be left in because it will probably work with fixed drivers on future GPUs?

Perma-Broke Apple AMD OpenCL Drivers

Its now 7 months of broken OpenCL drivers for the AMD GPU in the late 2016 Touch Bar MacBook Pro. (Since Sierra 10.12.4. Affects all builds of High Sierra.)

Metal drivers work correctly for the Mac’s AMD GPU, but some fractals (10 to 20%) render incorrectly. So I don’t recommend Metal as an alternative.  (Note: this incorrect render output is a new problem. Older Metal driver versions did not have this problem. The drivers in Q1 2017 worked so well. Now it is Q4 2017.

The legacy of Apple’s unusable GPU compute drivers goes on and on.

OpenCL/Metal Rendering on Intel GPUs Works !

Fractal Architect version 4.5.0 submitted to Apple today (Dec 14, 2016) makes it possible to use either OpenCL or Metal GPU rendering with Intel processors.  This capability requires Mac OS Sierra.

With Mac OS Sierra, it seems that all Intel CPUs (2013 and later) having Intel HD, Intel Iris, or Intel Iris Pro GPUS can now take advantage of either OpenCL or Metal  rendering for HUGE speed increases. For example, a 2013 MacBook Air gets approx. a 9x speed increase !  That is like a baby going from crawling to Olympic sprinting.

On Macbook Pros and iMacs having both a discrete AMD GPU and an Intel processor with its integrated GPU, you can use both GPUs together for rendering. This gives you almost twice the rendering speed !

Thank you Apple for giving us great OpenCL and Metal drivers on Mac OS Sierra !!

Note: Older versions of Mac OS and Macs produced in 2012 or earlier may have compatibility problems. (But CPU rendering works fine.)

Metal Rendering on Intel, AMD, & Nvidia GPUs Works!

Sierra Metal is Working Well on AMD and Nvidia

With Sierra coming out shortly, Metal renders can be made on all 3 GPU platforms: Intel, AMD, and Nvidia using Fractal Architect 4 version 4.4.0.

Apple has done a very good job on the Sierra release. In general, Metal is working well, and for some older GPUs, OpenCL rendering now works again (El Capitan’s OpenCL drivers were so broken).

Both Mac OS El Capitan and Sierra support Metal rendering, but the quality of the Metal drivers varies depends on the specific GPU configuration and OS version used.

For example, on Sierra the AMD drivers are much faster than on El Capitan.

On 2013 Mac Pro, with 2 AMD GPUs, you can use both GPUs for even more speed using Metal (but OpenCL driver has a critical bug preventing usage of more than 1 GPU).

Warning – Sierra Metal may not work on your GPU

On El Capitan, my 2013 Macbook Air renders 10.5 X faster than CPU. On Sierra, the Metal compiler cannot compile the app’s kernels on the 2013 Macbook Air, resulting in no GPU rendering at all !

But 2015 Intel Iris Pro in Macbook Pro works great with Metal !

Evaluating Sierra First

Since GPU compatibility is so hit and miss, I recommend installing Sierra first on an external hard drive and trying it out on your Mac(s).

You boot off that external drive by holding down the Option key at boot and select the external drive from the list shown at boot time.

Since normal hard drives are so SLOW, I recommend the following external drive: Samsung 250 GB T3 Portable SSD. This has worked very well for me, and the cost is reasonable.

Evaluate both OpenCL and Metal

Apple’s OpenCL drivers have been very good on AMD GPUs, but don’t work at all on Intel GPUs. But that OpenCL on AMD, may be faster than Metal on AMD. So remember to try both to see what works better.

Intel GPU Rendering now works on all Macs since 2012

This is BIG News !

Fractal Architect 4  now fully supports Metal GPU rendering on all Macs built since 2012 (using the Mac’s Intel GPU). Version 4.3.3 of FA 4 has some critical fixes.

Last October, we reported issues with Metal rendering. Those issues have been resolved in version 4.3.3 of Fractal Architect 4.

With the latest Sierra Beta, OpenCL GPU rendering now works on Intel GPUs for the first time too.

The rendering performance increase is HUGE.

El Capitan 10.11.6  Performance using Intel Metal

2013 Macbook Air     10.5 X faster than CPU
2015 Macbook Pro      4.8 X faster than CPU

Version 4.3.0 Submitted to Apple for Review

New Features

New Render Modes

  • Normal, Transparent, Composite over Background Image, Composite Over Color

Drag and Drop any image (even other fractals) to make it the Background image (for compositing).

Control transparent image’s alpha mask using new AlphaGamma parameter.

Preview window has fixed aspect ratio for fractals with composited background image – same aspect ratio as the background image.

Render to File dialog boxes show the compositing background images width and height (and sets the output image’s width and height to the same values.

Continue reading Version 4.3.0 Submitted to Apple for Review

FA4 version 4.20 released


  1. Metal rendering support for Intel Iris and Intel HD GPUs on OS X El Capitan.
  2. Metal rendering does not work for all fractals.
  3. Metal rendering not supported for AMD and Nvidia GPUs at this time.
  4. Added Gpu Compatibility Report to GPU Trial Window
  5. Removed color matching code not compatible with OS X El Capitan
  6. Removed color out-of-gamut check and soft proofing from Preview window not compatible with OS X El Capitan
  7. GPU Trial window now has Enforce Quarantine checkbox.
    Turning it off allows you to do trial renders on quarantined GPUs.
    Alert shown when you turn off the quarantine.

Metal rendering can cause GPU hangs for certain fractals (about 10% of them). GPU hangs cause your Mac to freeze for about 10 seconds (while the GPU restarts).

Normally, we would not have released this enhancement with the potential GPU hang issue, EXCEPT that on Intel GPUs the render speed performance is really good.

For those of you on Macbook Airs, we are getting 9 to 12X faster renders. You will experience GPU hangs with some fractals, but you always have the option of rendering those on the CPU — slower but robust.

Because of this GPU hang issue, Metal rendering is ONLY used in the app where you render a single fractal at a time – Preview window, Render to file, Quicklook.

Note: Intel HD 4000 (an older GPU) Metal rendering does not work on El Captitan 10.11, but it does work on 10.11.1 Beta. Its a slow GPU, so the performance is only 40% faster than on CPU.

Metal Rendering On OS X El Capitan

Version 4.2.0 of Fractal Architect 4 adds GPU rendering support for Metal on OS X El Capitan.

Lets be honest about the state of Metal Compute on Mac OS X in the initial release of El Capitan OS X. There are a lot of critical issues on all of the GPU platforms, AMD, Nvidia, and Intel. Only the Intel platform is stable enough to support this app’s flame fractal rendering algorithm. But it has significant issues too.

Render Performance using Metal on OS X El Capitan GM

(Mips is Millions of Iterations per Second an internal app measure, that is directly related to render performance)

2013 Macbook Air using Intel HD 5000 GPU

CPU: 10.01 Mips
GPU: 87.60 Mips     8.75X faster than  using  CPU

2015 Macbook Pro with Intel Iris Pro

CPU:  25.68 Mips
GPU: 124.09 Mips   3.42X faster than using CPU

The 2015 Macbook Pro also has a AMD Radeon R9 M370X GPU. Here are the rendering speeds for it on OpenCL:

Yosemite 10.10.5      AMD GPU:        157.83 Mips
El Capitan 10.11 GM   AMD GPU:          87.92 Mips

Note that the OpenCL driver performance went down 45% from Yosemite to El Capitan – NOT good!

Important Note: We are experiencing GPU hangs with some fractals  using Metal Compute.  GPU Hangs are the bomb. Entire Mac acts like it has frozen for about 10 secs until GPU resets. This behavior is unique to Metal Compute.

Metal Compute Stability seen in testing

GPU Family Test Results
Intel Iris Pro GOOD:
+ Intel HD 5000   Performance 9 to 12X faster than CPU
  GPU Hangs on about 10% of fractals
  OpenCL drivers have no problems with this
Intel HD 4000 BAD: Very slow kernel compiles
GOOD: Performance 1.4X faster than CPU
AMD BAD: Kernel compile failure at 2 min 20 secs
Nvidia 650M GOOD: Kernel compiles in 5 secs
BAD: Garbage Output

FA 4 4.0.3 release submitted to Apple

A new update release of FA 4 is on the way.

  1. Fixed camera rotation animation
  2. Updated Intel GPU quarantine for new Mac models
  3. Made random generator’s garbage filter settings less confusing
  4. Random generator now has Reset Settings to Defaults button
  5. Random generator now has limit of 200 random fractal retries
  6. Animation configurator’s video preview popover stays open now
  7. Changing Sequencer segments’ offset an/or duration now works correctly
  8. GPU Trial window now always reports performance multiple as GPU Mips/ CPU Mips
  9. Render State window now reports the Initial Mips performance (so you don’t have to go to the Render Status Log to find it)

FA 4 Version 4.02 Released

Release Notes ===============

Bug Fix: for Loop/Morph Basic Animations being classified as Complex animations
Bug Fix: for Gallery fractals not rendering
Bug Fix: for final assembly of movie failing with sandbox exception
Bug Fix: for Quicktime Player not opening after movie rendered
Bug Fix: for Make Video not working with either variation weights or variation parameters