The render engine analysis series: Redshift

12.10.2017 Home >Blog >The render engine analysis series: Redshift

In this series, we take you through some of the different render engines that are out there. There are plenty of them, all with their perks and downsides. This series explores Arnold, V-Ray, mental ray, and Redshift – all for Maya 2017. The lighting set up will be the same, and we’ll see if it’s possible to get the same results.
In this scene, our Render Wrangler Iris will use a HDRI for the overall lighting, four lights at the doors to mimic strong light falling through the door openings, and some extra small lights to highlight details or to light up the overall scene.

Redshift is a render engine that is fully GPU-accelerated and biased renderer. What this means is that it calculates approximates and interpolates light to give a grain-free result.

I have never lit a scene with Redshift so this will be an adventure for both of us. I will once again create my basic set up but probably render a bit more often to see my progress.

I will start off with a Redshift rsDomeLight, link the HDRI in the dome map and render.

Redshift 3D render of a barn

Very dark and mysterious, I’ll give you that! Let’s have a look at the settings, as there are quite a few things we can tweak. I would not touch the gamma for now and first try to achieve a lighter scene through exposure and adding lights. I am going to double the exposure to 2.0.

This is a good point to start from I think. It is not too bright but we can see some nice light come through the door openings and the little window in the back. We can see some bounce light on the ceiling so this is looking good so far!

As with the other setups in Arnold, V-ray, and mental ray, I am going to bring in my four lights at the door. I am setting them to temperature mode at 5000.00. For now, I will leave the intensity at 100 as this is the default start point and as good a starting point as any. On my first render, I did not get any light coming in through the left-hand door openings. I tried to increase the intensity but this made no difference. I looked at the object in my viewport, but I don’t actually get a light shape. Nevertheless I tried turning the object around 180 degrees, and sure enough, there was the light. This just goes to show how important it is to check if your lights are pointing in the correct direction!

What a lovely result – and how nice to see the 2 lights within the front door openings not completely merging, but having those nice hard edges. We can soften them up later if we want to, and we probably want to, but for now it is convenient to see where exactly the light hits the surfaces.

Although this result is good, I do not like the black shadow in the right-hand door opening. We do not have to up the intensity; instead, I will move the light a bit and see if this gets me the result I want. And sure enough, it makes a huge difference on where the light goes.

(Old position in the upper half, new position in the lower half)

The next thing on my list is to make the overall scene a bit lighter using an ambient light. Here I discovered the first thing that I do not like about Redshift. It does not pick up the “normal” lights from Maya. I just want to pop in an ambient but this does not work, so I have to think of a way around it with the Redshift lights. Nothing a bit of rational thinking won’t solve!

An ambient light is a sphere-shaped light that emits light without decay. That could be a great solution, so let’s make it. I create another rsPhysicallight and set the shape to Sphere. I switch decay to none, and the multiplier to 0.1.

There we go, now to get rid of the grey globe a.k.a. our ambient light. Go to the lightshape in the attribute editor and under Area, untick Visible.

Time to tackle some of that grain. A good thing to note at this point is that the render time is a lovely two seconds. As I am going to increase the samples on the lights it would be good to monitor and see how this affects the render time. As per default the samples are set at 16, so I am going to double that to 32 and see what happens.

(32 samples, 11 second render time)

This is not really a grand improvement, but my render time went up by almost 6 times. If you start from 2 secs this is not really an issue, but if it was 2 minutes and you go up to 11 minutes, it starts to get annoying. I have undone this for now and set everything back to 16. I think a different approach might be better, perhaps adding in some more lights. I will do one more of my self-made ambient lights a bit closer to the camera. Now the lights are almost the same as in my previous set up, I just need a little more light to soften the shadows on the walls.

I have added in yet another physical light as these seem to be the most versatile and do the job, and this one is placed just behind my render camera. I have set my 2 “ambient” lights to have 32 samples as they do take away a bit of the grain, and I have set their light decay to linear instead of none as I want a bit more darkness on the back wall. When I render, I get the following result. Current render time? 9 seconds.

As there is still quite a bit of grain, let’s have a look at the global render settings and see if we can fine tune the image some more. The first tab I am going to start at is the Output tab. Here I am going to increase the minimum and maximum samples to get rid of it. I have started with raising the min samples to 16 and the max to 128.

And I love Redshift again! Although it is a bit fiddly, especially as you cannot use the Maya lights, it does give you beautiful shadows right from the default settings. The light and shadows blend beautifully and are quite easy to manipulate. I have not even started to fine tune things, but even now I feel that I might get away with leaving my render like this. Although it did raise the render time from 9 seconds to 35, I feel that it is really worth it. And to be honest, 35 seconds is still almost nothing.

I have tried going up another step, min to 32 and max to 268, but for me I don’t see a huge difference and therefore it is not worth the extra render time as render time is now 53 seconds.

This is all I am going to do in the render settings. I am not going to touch any of the overrides or filters, as I don’t believe they will be very useful at this point, and any changes might just mess it all up. So, this is it. The final render. I am happy and it falls well in line with the other renders. The rendering speed is much reduced, and I am sure once you have worked with it a few more times, setting up a scene with the lights will go a whole lot faster.

What do you think of the way that we lit and rendered this still? Have you fallen in love with Redshift like our Render Wrangler? Would you rather have more detail and a much longer render time? Make sure you read our results to see which render engine is best for you!



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