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The personal site of Jamie Knight, an autistic web developer, speaker and mountain biker who is never seen far from his plush sidekick Lion. View the Archive

Topics: Autism Development

Experimenting with Blender on the iMac.

It’s been about 10 years since i last did any experimentation with 3D graphics and rendering. At the time i was using a shared PC and demo software. I got good at building my scene as i had to rebuild it every time because the save feature was disabled!

A few weeks ago i decided to start playing around again to see how the modern tools and tech compare. I have my very lovely 5k iMac so i wanted to see what it could do.

Why Blender?

Blender is an open source 3D modelling, animation and rendering tool. It’s been used to make a range of 3D movies and also in adverts etc.

It’s free to use so it felt like somewhere useful to start. I don’t have any specific goals in mind, but i figure if i learn how to use it i will start to find uses for it.

At the very least its a distraction and a useful way to spend my time in the evening.

My experiments.

My interest is more technical than artistic. I am interested in how the technology works, especially around the use of “ray casting”.

Raycasting is the process of simulating light inside the computer. Unlike older rendering methods (rasterisation, like in games) it’s attempting to replicate the physics of the real world and can in turn give much better almost photorealistic results.

At this stage my experiments are just the basics. Getting some models, rendering them, playing with some animation and understanding the tools a bit better.

The rest of this post is a summery of what i have learnt so far.

OpenGL, OpenCL & CPU.

The rendering system used within blender is called Cycles. One of the first things i have learnt about is that there are three types of rendering cycles can perform. It can either:

1. Render on the CPU – this is the simplest, just use the CPU to do all the maths needed to simulate each light beam.
2. Render using OpenGL – treat the scene like a game and render it using rasterisation. This gives more a more cartoon and game like feel and is really quick. All the previews are rendered this way.
3. Render using OpenCL (aka GPU Compute) – this uses the GPU in a different way. It uses the programmable shader inside the GPU to do ray tracing. The shaders are not very quick, but there are thousands of them, so they can accomplish lots of throughput when the problem is right.

On my iMac, i have been using OpenGL rendering when making preview videos etc, and then using CPU rendering when i want to have the high quality rendered output.

My iMac does support OpenCL rendering, but its really slow. By all accounts this is due to terrible drivers. I may install Linux on my iMac and see if that works better.

Samples and tile size.

With the raycasting options the main quality setting is the “sample” rate. In effect this is how many beams of light to use when simulating the scene.

There no “perfect” value. It’s always a trade off between quality and performance.

For example, my first experiments involved rendering some wallpapers for my iMac featuring Vincent one of the free blender assets. As this render is zoomed in close and Vincent has lots of detailed textures, it took around 600 to 1000 samples to look good. Below that the image is fuzzy / noisy.

However, for my animation experiments the sampling can be much much lower and it still looks good. My first rendering used 24 samples and was okay but a bit fuzzy. I have experiment around and 50 samples looks much better. At 100 samples I couldn’t really tell the difference anymore.

My animation is only 100 frames long. However, the difference in performance between 50 and 100 frames is astounding. The first frame at 50 samples took 11 minutes to render, and at 100 frames to 32 minutes.

With that in mind i am now re-rendering the scene at a sample rate of 50. It will look much better, and hopefully not to too long to render. To help speed things up i am also experimenting with parralism.

User a render node.

I have two Macs in my flat and they are connected together with a Thunderbolt 3 cable. Both Macs have modern quad core i7 processors.

Given i have the extra mac i have started experimenting with splitting up the rendering so it can be completed quicker.

I know Blender has a proper tool for this, but for now i am keeping it simple. I render the first 50 frames on my iMac, and the second 50 frames on my Mac mini.

I am going to explore these options further. I am sure as i experiment more with the tools i will need more render performance so being able to make the most of my hardware is essential.

Final thoughts.

It’s been fun to explore blender and cycles. I have a few future projects in mind but mostly i am just enjoying the new technology and learning. I have time in the evening and its fun to use to too play with new technology rather than just consume media.

Published: 27 April 2017 | Categories: , Permalink

iPad 5th Generation First Impressions

I’ve had my new iPad a few weeks and its been really interesting to play with it. Unlike my other iPad or the macs in my life, this iPad is a purely personal device. It’s something for me to use when I want to escape my day job and freelance commitments and just be a technical muggle.

To this end what I need is pretty simple. Something for lots of web reading, some social media and instant messaging. The occasional bit of writing and a game from time to time.

It’s too soon for me to review this thing, so here’s my first impressions.


The 5th generation iPad is a unapologetically mid range device. Low to mid range devices are one of the most interesting places for the design. The budget forces compromises and difficult decisions. I think on the whole the iPad gets these compromises right.


The iPad is not fast. It’s not slow either, but too me (a 12” iPad Pro user!) there are noticeable delays. It’s just not as snappy as the pro model. I see the difference most when loading applications and when scrolling pages with adverts / animations. It’s not a big stutter, but its certainly not as butterly smooth.

However, this doesn’t really seem to matter that much. I brought the cheapest model I could get and I don’t intend to keep it all that long. It’s well under half the price of the iPad Pro 12” but it has 80% plus of the performance. That’s a bit of a bargain!

The one concern I have with performance is service life. I’m hoping to get at least 2 years of use out of this iPad and i am not 100% convinced the performance will be good enough after an iOS update or two.


Another places where the iPad is “mid range” is in the display. Unlike the iPhone, iPad Air 2 and iPad Pro there is a noticeable gap between the “glass” and the screen. In other words, they are not laminated.

Much like with the performance, the difference is noticeable, but its not really a huge issue. In day to day use the gap does not bother more. It has an upside too, if i break the glass a replacement is much easier.

One area which is already annoying me is the reflectivity. I am using the iPad in exactly the same places as my iPad Pro and the difference in reflectivity is noticeable.

So much so, for the iPad i am running it at almost full brightness whereas the iPad Pro is running at barely half brightness. The lack of the anti-reflective coating is a day to day annoyance.

Form Factor.

The size and weight is fine. It feels positively tiny and portable compared to my iPad Pro. Unlike this pro, this iPad can be used on the sofa or while standing.

A nice bonus the smart case i brought when i borrowed an iPad Air fits great. That’s a small thing, but it did help save me £40 which is not a trivial amount of money.

h4. Other.

Touch ID and Apple Pay support are really nice additions. They help round the iPad out and just make it that little bit more useful and flexible. I’m glad Apple added them.


The iPad version is iOS is a pretty well known quantity now. It’s still got some rough spots (multitasking!) but in general its fine. I can be productive with it when needed (like writing this post) but mostly i am using it to just surf the web etc. For those tasks it’s excellent and the app support is second to none. There is normally an iPad version of any app i look for.

As this is a personal iPad i am sometimes using it for gaming. I have been impressed with the quality of games on the iPad. I have been playing hitman go and really enjoying it. The graphics are very pretty and the simplified gameplay really works for me.


This iPad cost me £339, which is a huge saving over the £540 my last 9.7” iPad cost me. The 32gb storage space is not idea but for the money its fine. At least its better than the 16gb Apple used to offer on the entry level iPad.

Compared to the iPad Pro the new iPad is great value. It’s damn near half the cost once the smart case is considered. This might be the best value Apple device i have brought in years.

Final Thoughts.

My first impression on the new iPad is really positive. It’s a capable little device sold for a very fair price. It’s “good enough” and it suits the needs for my personal computing wonderfully.

Unlike the iPad Pro, this iPad isn’t trying to be a Super Computer. It’s a good device and that’s all it needs to be.

Published: 18 April 2017 Permalink

The iPad Boring

A few weeks ago Apple announced the iPad Boring via a press release. It was not a big announcement for Apple. Much like the iPhone SE the “iPad 5th gen” was a mid market device designed to fill a gap in the market. A design from 2013 stuffed with internals from 2016. To those waiting for iPad Pros it was a very disappointing update.

However, to me it was pretty darn interesting. I had been looking for a “home computer” for a while and i didn’t know it was iPad shaped.

Home Computer.

I am fortunate enough to be surrounded by amazing hardware. I have an iMac, a MacBook and (via the BBC) an iPad Pro. Thats almost £4,000s worth of hardware and i am grateful for it. My devices support my work and that keeps me fed and housed etc. All good things.

However, theres a snag. All of those devices serve double or even triple duty. None of them are really “mine”. They belong to my employer, or my company, but not really to “me”.

This is not the first time i have found myself in this position. For ages, i used to have a MacBook Pro for work and an iMac or a MacBook Air at home. I started this way back in 2011. At the time i even had this handy definition of a home computer:

For me, my home computer is the computer which i am unable to work on. It doesn’t have my software tools installed at all. My home computer is what i use once i get home to check on twitter, Facebook etc. […] I also use my ‘home’ computer for non work projects, such as study or researching lego parts.

Since getting ill my work life and my home life have merged. I certainly don’t need another Mac in my life. But i have been wanting something all of my own.

Enter the iPad Boring.

I want my personal computing to be effortless. Something i don’t have to think about or maintain. Something “good enough” is fine. The fact i cant load all my software tools onto the iPad Boring is a good thing! It does run my speech software, so the important stuff is covered.

Secondly, the iPad Boring is cheap. At £339 its a third of the cost of even an entry level MacBook and almost a quarter the cost of a Mac i’d actually want to own. If i get two years use of it then donate it to relative i’d be pretty happy.

I think thats everything. Long live the iPad Boring!

Published: 12 April 2017 | Categories: Permalink

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