Images produced by 3D rendering software require further finesse – post production is where precise fine tuning occurs.
There was a time when this topic did not exist for most 3D architectural renderers. We simply hit the “render” button and the image or animation that resulted was the final product. The use of post production techniques migrated from movie production studios, in particular all-digital studios like Pixar. The enormous positive effect these techniques have had on architectural visualization cannot be overstated.
What it is and Why it’s Used
The definition of post production varies with the thing being produced. Music, movie and TV producers all have different post production processes. The definition of post production as it pertains to creating architectural visualizations is the manipulation and elaboration of the 2D imagery output by the 3D software. If the end product is a still, post production means fine tuning the image’s color values, sharpness, saturation and other visual properties. If the end product is an animation, post production manipulates the same properties as the still but can also mean the addition of sound effects, music, narratives, text overlays, etc. There are three main reasons for using post production: to fine tune the image, to allow quick edits without having to re-render, and to add effects that can’t be produced by 3D rendering software.
The main method that architectural renderers use to refine their images is compositing. Compositing is the use of software such as Adobe Photoshop (for stills) or Adobe After Effects (for animations) to separate an image into distinct layers with the aim of isolating edits to that layer only.
Let’s illustrate with an example. Figure 11.1 shows the final rendering of the house we’ve been using throughout this guide. We want to brighten the sky – and only the sky – and give the slightest hint of glow at the edges where the sky meets the foreground objects. This manipulation replicates an effect that occurs in actual photographs. Real skies radiate light energy across their entire surfaces and cameras record this luminance; the virtual 3D cameras that create computer generated renderings don’t. (This is only partially true; some 3D rendering programs can record this effect, but it’s easier and more efficient to control it in post production). Knowing beforehand that we wanted to brighten the sky in isolation of everything else, we rendered the sky on its own layer. (All professional grade 3D software provides a toolset to render in layers like this) By pulling this sky layer into our compositing software, we select the area of the sky and adjust the brightness of the sky only, leaving the rest of the image unaltered. The glow around the edges requires a couple of steps more, but is achieved using the same layer.
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This example illustrates the base method used for all post processing – isolate an image component, adjust it, repeat for other areas until you’re satisfied with the result.
There are dozens of manipulations that can be performed in post production; here’s a list of the main ones that concern architectural imagery:
- Adjust hue, saturation and brightness of the entire image or selected areas. For example, we can increase the contrast of an entire image or change the color of selected walls and make them brighter or darker.
- Add optical effects. The physics of light bending through a lens causes real-world cameras to distort the images they record. These are known as optical effects and they include lens flares, halo glows, depth of field and motion blur. Optical effects are not typically rendered by 3D cameras – they can be, but it’s not the most efficient way of achieving this effect. We can introduce all of these effects in our compositing software efficiently, and if we decide that they need to be changed or eliminated altogether, we can make these changes without having to re-render.
Rendering in Layers
Besides allowing layer-based image editing, the other huge advantage of using post production is that it allows us to make changes without having to re-render. In the Rendering section of this guide, we discussed the impact that rendering final images can have on a production schedule. Render times – that is the amount of time a computer requires to produce an image – can be very long for final images. If we have to render and re-render final images, our whole production pipeline can get clogged. Combining a smart rendering strategy with the image manipulation that compositing software makes possible, we can make many revisions without having to re-render. Need to quickly fine-tune the color of a wall? No problem. And no re-render. Need a last minute change on the saturation of the shrubbery? No problem, and no re-render. No problem, this is, if we use a smart rendering strategy. Our studio uses the following rendering/layering strategy. It helps us maximize our render quality and minimize re-renders:
For Exterior Renderings:
- Architectural & Site Layers – when a client has given official approval to the 3D model, texturing and lighting, we render the architecture and site. Layers for trees, shrubbery, sky, background, foreground, etc. are all turned off. The architecture and site layers are the most “expensive” in terms of render time.
- Landscaping Layers – trees and shrubs need a special set of post processing to get the look right. We also find that this part of the image needs to be carefully balanced with the architectural layers so as to not overpower them. This is usually the second most expensive layer in terms of time required to render.
- Background Layer – usually this means the sky, but it can mean anything that shows up in the background of the image, for example, distant trees or buildings.
- Special Effects Layers – This usually means grass. It can also mean things like fire in a fireplace, water trickling down a fountain, fireworks for a Fourth of July night time rendering, etc.
- Car Layer – experience has taught us that clients can be very particular about the location and type of cars. We therefore render them separately to avoid lengthy re-renders.
- People Layer – like cars, the placement and characteristics of people can generate strong opinions. By keeping them on their own layer, we maintain maximum editing flexibility.
- Illuminated Object Layer – if we are creating a night time rendering, anything that is a source of illumination is rendered separately. This way we can add a touch of glow around the edges.
For Interior Renderings:
- Architectural Layer – just like for exterior renderings, when we have client approval for the 3D model, texturing and lighting, we render the architecture. These renderings look like a vacant home. The layers with furniture, window coverings, area rugs, people, plants, etc. are all turned off.
- Furniture Layers – depending on the type of furnishings that are to be rendered, we sometimes break this layer into sub-layers. For example, some types of fabrics might require specialized image enhancement in our compositing software, so these objects will be rendered on their own layers. Semi-opaque window coverings that have strong sunlight showing through are another example – these require further editing in the compositing software to get the look right.
- Illuminated Object Layer – anything that is illuminated is rendered on a separate layer. This way we can add a touch of luminescent glow to enhance a sense of photographic light.
- Miscellaneous Layers – this usually takes the form of specialized renders that can add subtle enhancements to the image. One such render “pass” helps emphasize corner and edge spaces, helping to give a room or building a crisp, clean feel.
Most 3D software packages allow the user to isolate “elements” that are created as part of the underlying image calculation process. For example, 3DS Max’s native renderer and the rendering plugin that our studio uses – V-Ray – can output layers that isolate shadows, reflections, refractions, velocity, luminance and some 25 other layers too esoteric to name. This allows a further dimension of surgical precision control over the final image outcome.