Real-time VR rendering

Editorial Type: Interview Date: 2021-04-01 Views: 4,646 Tags: Software, CAD, Rendering, Visualisation, Architectural, CADSchool, Twinmotion, Lumion, Endscape PDF Version:
Steve Brann, MD of CAD School UK looks at the capabilities of the top three real-time 3D rendering applications: Twinmotion, Enscape and Lumion

Once upon a time a rendering of a 3D model of a house with real 3D trees, grass, people and cars could take several hours - and that was just for a still image. Add a walkthrough animation and we are talking days of rendering, and adding more than a few trees with thousands of polygons would send most machines into a flat spin!

That is now a thing of the past. Now, we have real-time rendering apps that use powerful graphics cards and gaming engines to render scenes. Scores of trees, people and moving cars can be added without bringing the system to a crawl, and direct links to the CAD system of our choice mean that the workflow is fast and efficient.

On top of this most of them are as quick and easy to learn as they are to render. At CAD School we have been teaching people to use render programs for over 20 years, and most classes for render engines such as V-Ray and the Cinema 4D render engine utilised by Vectorworks used to take well over a day to teach fully. Not so with these new programs, as a couple of them can be mastered in well under a day!

Output from these apps not only covers the main bases of stills and walkthrough animations, but two of them allow you to put on VR headsets and walk through them in real-time, or create 360 degree movies, providing another form of VR using Google cardboard devices. The third app only provides static panoramas. Before you invest in VR, I thought it would be helpful to provide an outline of which app does what.

The three apps which we come across most frequently in our industry are Twinmotion, Lumion and Enscape. To use any of them successfully you will need to have a high end graphics card in your PC. If you intend to use a VR headset then you are venturing into gaming territory. Large models will also require large video memory which usually goes hand in hand with the better cards. If you want to find out if you have a good enough graphics card head to: A score of 10,000 plus is what you'’re after! All three apps will work with lower spec settings, but investing in a new PC or graphics card will pay immense dividends in terms of design performance.

Twinmotion is the only one of the three to also run on Macs as well as PC's quite adequately with discrete graphics cards. However, to use VR headsets you will need to be running Windows. Lumion and Enscape are only Windows based.

A key area for all three apps is their ability to import and synchronise models with the rendering engine. Lumion has two ways of achieving this - LiveSync, as the name suggests, ports the model directly from the modelling software into Lumion and automatically updates the rendered view as the model develops.

All of the major AEC applications - Vectorworks, Archicad, Revit, Bentley - have LiveSync plugins, as do SketchUp, Rhino, 3ds Max and AutoCAD, and models are imported in a number of formats - Obj, Collada, Dwg, Maxfile and SketchUp.

The import function not only allows import of the main model but additional components and features, such as furniture, trees and people or secondary buildings. Rendered scenes are updated from the latest version of the building model with a single click. I have seen on some forums and blogs that there are many seasoned users who prefer the import function for their main model as it gives them more flexible control over the model density.

Enscape only uses plugins to the modelling software and most of the control of the software, such as materials and additional entourage, must therefore be done in the host modelling program.

Like Lumion the view can also be synchronised or disabled. All imports are therefore handled by the host program and the use of Enscape is limited to programs with a plugin, with the Enscape window becoming merely a render window. Plugins are however available for the four main modelling programmes and Rhino.

Like Lumion, Twinmotion has both Dynamic Link plugins and imports that can be updated, but unlike the other two applications Twinmotion neither maintains the model nor the view in real-time. If the model needs updating then you must click on the Dynamic Link plugin or else export using a supported format and update the imported file. Dynamic Links are available with Revit, Archicad, SketchUp, Rhino and RIKCAD, with a version for Vectorworks probably becoming available in their next software release (until then you can use Cinema 4D export).

Twinmotion can import all types of components - models, landscape, people and furniture features - in a very wide range of formats.

All three programs have a good array of textures that support the usual colour maps, reflection, alpha and bump maps. Lumion now additionally supports relief maps, but only for its own materials. Although reflection is supported by all programmes, refraction is only supported by Enscape. Lumion's texture library is stacked, with over 1200 different materials, and its extensive material libraries probably account for its higher cost.

In terms of render quality all three do a great job of producing realistic exteriors, which, interestingly, are less demanding than interior renders, which have to cope with soft shadows and textures. Outdoors, the ability to accurately simulate the sun's position and build realistic skies all help to give great renders for all three apps, but here again there are differences.

All three applications offer accurate lighting that respond to the sun's position to give appropriately hued skies, as well as sunrises and sunsets. Enscape has some detailed sliders for the type and quantity of cloud cover you want, whereas Twinmotion can set a wide variety of weather patterns including rain and snow, if set in winter, which appropriately covers the entire scene in snow. Lumion has an alternative sky option called Real Skies which utilises HDR skies. They do not directly respond to the sun but instead provide 41 alternatives for different times of the day and different weather conditions. Their realism is striking but they do not have moving clouds and won't allow for animating the time of day.

This is the heart of all exterior scenes and is something that would normally bring a render program to its knees. With a decent graphics card and plenty of memory all three programs can handle copious amounts of trees which really need to react to the wind for convincing animations.

This is arguably Enscape's weakest area. Its trees wave in the breeze with the rest of them but the placement of trees is done one at a time whereas both Twinmotion and Lumion have tools to paint forests in seconds. Enscape's tree library is somewhat limited, but growing…

Twinmotion has some lovely plant tools that effectively paint plants and trees in layers that can be added to and erased in bulk. The trees also have a unique trick up their sleeves in that they all have different growth stages and respond to the seasons with varying amounts and colour of leaves and even turn white in the snow.

Lumion makes up for these features by simply having a huge library of trees - about 700 varieties just in the broadleaf section alone - but they don't respond to the seasons, which puts it in the shade compared to Twinmotion. There is a filter called Autumn colours but it is far from ideal.

Each app handles grass differently too. Lumion has some fantastic ready made lawns with all sorts of stripe patterns. Enscape has the simplest grass of all which just shows variations in height, but Twinmotion has the ability to paint with layers of grass in a number of varieties, some of which include wildflowers.

A critical part of each scene, addressed by all three apps, is the range of objects they are able to place - which can, of course, be supplemented by importing models from external databases. Lumion excels in the size of its library department but size is not the only factor here to consider here.

Twinmotion has some real aces up its sleeve here. Cars and people can easily be made to travel along roads and not just singly either, as they can use multiple lanes or paths and go in both directions with varying densities and speed. Building a public scene to include animated cars and people really sets Twinmotion apart from its rivals! You can use Lumion to animate a car, boat or plane along a path but only individually, and the models of people also have some animation capabilities. Enscape, however, cannot animate moving objects at all.

At this point I originally thought that Lumion would have to be excluded, because of its shortcomings in the Global illumination (GI) department, but by digging around I discovered their GI effect, and with a lot of effort eventually managed to turn it on and get it to recognise the two spotlights I had placed in the scene.

In Twinmotion and Enscape GI works out of the box in real-time. Twinmotion, however, uses what it calls Screen Space GI, which only shows the bounce of a light if the light is visible in the camera. This means that in animations lighting effects can change significantly as viewpoints shift, but otherwse the function is simple and effective. Reflections in Twinmotion are handled in the same way, and you can only see the reflection of objects visible to the camera. To finesse or improve these effects, you can add reflection cubes or domes.

All three solutions can easily output stills, animations and panoramas. Lumion has online cloud storage called MyLumion which can be used to share rendering tasks with colleagues, mainly used for panoramas. Walkthrough animations are very easily made in all three programs with keyframe based animation. Twinmotion can also render 360-degree videos in which the viewer can decide where to look. You can view these using Google Cardboard devices - a very cheap way of doing VR using your own phones (the Cardboard glasses typically only cost about £20 - £30).

The real deal here however is when you plug a dedicated VR headset such as an Oculus Rift or HTC Vive Pro into your system. Now we're talking! When I was able to show Paul Bulkeley of Snug Architects his amazing design for the Eternal Wall of Answered Prayer on the HTC headset his gob was well and truly smacked. "The client has got to see this" he said, "Wow, this is awesome!" The video of him walking around the design and his reactions are the only demo video you need to see. it is certainly another dimension and not one that is easy to illustrate in a review or on a website.

Lumion is not really a contender in this area. Both Enscape and Twinmotion can switch to viewing through VR headsets in seconds. Using the two HTC Vibe controllers you can instantly transport yourself to anywhere in the model and from there walk around within the limits of your VR room, or 'teleport' instantly to anywhere else in the building.

You might be surprised. Twinmotion, the solution that promises the most, is the cheapest of the bunch and is available on a perpetual license per user and, surprise, surprise, we are offering a special deal through CAD School until the end of the year for £263.00 plus VAT. Enscape is available for £351 plus VAT for an annual license, but Lumion comes in two versions, the Standard one with limited libraries, for £1345.00 Plus VAT, and a Pro version for £2690.00 plus VAT. As I said earlier, its higher cost reflects the amount of material libraries that come with it. Don’t forget to add in the cost of acquiring libraries of materials and components from elsewhere if you need them.

It all boils down to what you want to achieve and which app is available to provide it. I am happy to provide further advice, or enrol you in one of our courses to help you get the most out of your chosen solution.