Best Of

Lighting breakdowns

This write-up looks at how some of the fundamentals of photographic composition can be applied to render setups for presenting real-time assets. Since each render engine is slightly different this is less of a deep dive into the technical nuances of how things work and more of a broad overview of how to use certain render features to enhance the overall quality of portfolio images. Keywords to aid in searching for additional information are in italics.

Lighting is an important part of creating compelling compositions and environmental elements can have a significant impact on how light interacts with the subject. In traditional photography, natural lighting is constrained by things like time, weather, terrain and nearby objects while studio lighting is controlled by things like flags, bounces, modifiers and artificial lights. All of these environmental elements can be manipulated to visually sculpt the surfaces by controlling where the light and shadow falls on the subject.

In traditional art disciplines, this use of contrast to create depth is often referred to as chiaroscuro. So this technique has roots in prior media and art movements. How this is all relevant to real-time render setups really comes down to how physical based rendering is currently implemented and how most contemporary texturing tools default to image based lighting for render previews.

With IBL setups, most of the environmental elements are already baked into the HDRI sky image. So when authoring material textures, without a controlled [calibrated] lighting setup, it's important to cycle through more than one background to get a feel for how the material values will read under various lighting conditions. This type of simple, early lighting test can be used to catch potential issues that could arise from choosing material values based solely on how something looks under a single HDRI sky image that has uneven lighting with a strong color cast or a color temperature that doesn't match the final in-engine lighting setup.

Another reason to test several different options for IBL lighting is that color temperature and environmental reflections are storytelling elements. So, when it comes to picking a HDRI sky image for the final portfolio renders, it's important to choose one that fits the overall theme of the project. In general, when the goal is to create a narrative piece it can make sense to use lighting with a strong shift in color temperature but for most run of the mill portfolio pieces it's much safer to use lighting with a more neutral color balance.

All that said... Lighting trends are definitely a thing and following what's popular can be advantageous. The only downside is that it can make it a bit more difficult for portfolio work to maintain a relatively consistent appearance across a longer period of time. Which may or may not be important for certain roles.

Using sky images as visible backgrounds can be helpful for evaluating material values during the texturing process and can provide some broader context to the stylistic theme in certain types of narrative renders but it can also be very distracting when used as the background for final portfolio renders. Blurring the sky image can provide some separation between the subject and sky but it's still possible for large parts of the model to visually blend with the background. Which can make it difficult to pick up on the details in the silhouette.

A fairly common critique of sky backgrounds is that there's too much competing detail that makes the image look busy and tends to draw the viewer's attention away from the work that went into the asset. The longstanding consensus on this is that solid background colors tend to be less distracting than visible sky images. Using a dark neutral gray or dull white color as a background is often recommended as it helps improve the consistency of the presentation and will make it easier to read the shapes and texture details.

Subtle overlays like fine dust particles, long sparks, gradients and vignettes can be used to add some depth and visual interest to the background but the fine line between interesting and distracting can be quite narrow. When in doubt: keep the focus on the subject by using a background that's clean and simple.

On it's own, basic IBL can be pretty dull. Enabling additional render features like ambient occlusion, local reflections and global illumination can help increase the perceived detail of surface lighting effects by simulating more realistic surface reflections and shadow depth. Certain render features can have significant resource overhead and while they won't always be usable in-game there's few reasons to avoid using them to improve the visual quality of portfolio renders.

When using IBL and GI, it's possible that any distinct colors or forms in the sky image might produce localized color shifts or tint effects in nearby surface reflections. So it's often helpful to completely rotate the sky image several times to find the optimal position for environmental reflections. Adjusting the relative brightness of the environmental lighting, before adding any independent light sources, can help establish a baseline for just how much additional lighting is required to achieve the desired results.

Multiple dynamic lights with shadow casting and contact refinement do tend to increase resource consumption but the complete absence of shadows tends to produce bright surface reflections that don't match the way lights work in the physical world. While intentionally disabling these render features can work well for heavily stylized work and technical constraints often mean finding a balance between visual quality and performance, most portfolio renders aren't going to be constrained by performance targets. So for assets with realistic materials it makes sense to bias shadow settings towards maximum quality.

Perceived lighting quality can also be affected by the size of the lights. Using smaller direct lights will tend to produce highlights and shadows with sharp edges. Which creates a stark, artificial look that can seem unnatural when paired with outdoor environments or interior scenes with natural light components. Increasing the size of the light or the area from which the light is emitted will tend to produce softer highlights and shadows that mimic natural sunlight.

In theory, setting up studio lighting to mimic natural sunlight light is fairly straightforward: add a large light with a high intensity and rotate it so the highlight and shadow fall in line with the existing natural light in the environment. Reality is often a bit more complex. Incoming light bounces off near by surfaces and creates indirect lighting that lifts the value of areas that would otherwise be occluded.

IBL and GI help simulate this effect but depending on the environment and lighting style it may be necessary to tune both the direct and indirect lighting inputs to produce the desired results. Adjustments to other light settings like type, shape, intensity and color all tend to mirror the behavior of the light modifiers (bulbs, flags, scrims, gels, etc.) used in [studio] photography.

Basic lighting setups are generally given labels that describe the number of lights used in the scene. Single point lighting setups can be both simple and realistic but just because something is realistic looking doesn't mean it's going to be interesting to look at. In contrast to this, multi point lighting setups do tend to provide more options for creating visual interest but the use of additional light sources also introduces some unique challenges. Most of which come from having to blend highlights and shadows from competing angles while also managing any stray lighting effects caused by secondary bounces.

When it comes to basic studio lighting arrangements: One point lighting setups generally use a strong key light that's placed off to one side so it illuminates that side of the object while the shadow obscures the opposite side. Two point lighting setups generally use a strong key light placed on one side with a weaker fill light placed on the other side to boost the light levels in the shadows. Three point lighting setups generally follow the same lighting arrangement as two point lighting but with an additional rim light that's generally placed behind the subject to produce a visible highlight around the outer edges of the shapes.

These basic studio lighting setups can be modified to produce different lighting styles. High-key lighting is a good example of a lighting style that uses a modified 3 point lighting system where the key and fill lights have similar intensity levels and lights are positioned to minimize shadows. Low-key lighting tends to be on the opposite end of the spectrum. Often using single or two point lighting setups with strong key and rim lights that create harsh contrast between patches of light and shadow. So it's acceptable to adjust the type, position and intensity of each individual light to achieve the desired results.

An image circle's field of view will be determined by the focal length of the lens. How much of this image circle will be captured is determined by the size of the light sensitive media. Though there's been a wide range of film and sensor sizes, the de-facto standard format is usually represented by a 35mm film equivalent.

Some real-time render engines support using focal length as an input to drive FOV settings, which makes it a lot easier to follow photography tutorials without having to consult conversion tables. If an engine only supports entering FOV angles then it will be necessary to find the focal length and sensor size used in any particular photography tutorial and find a conversion table that provides the closest FOV angle.

Without getting too far into technical minutia, due to the differences between how the human eye and various camera systems function, there's several different schools of thought on which focal lengths mimic what the average person sees. A lens with a 50mm focal length is often quoted as being THE normal lens for 35mm film format cameras. However there are convincing arguments for using wider lenses. With 24mm being near or past the limit for acceptable distortion. More traditional thinking usually limits the range of widely accepted normal lenses to between 35mm and 50mm.

This all becomes important because, when a subject completely fills the captured area of the image circle, lenses with shorter focal lengths will tend to produce strong barrel distortion and lenses with longer focal lengths will tend to produce pincushion distortion. Some lens distortion is generally acceptable but too much outwards image distortion can create the illusion that the subject is much larger than it actually is.

Lens compression is used to describe the PERCEIVED difference in flatness between two focal lengths, when the subject is kept a consistent size in the image circle, by moving the position of the camera. Again, without getting into a very convoluted and often misunderstood phenomena, the basic idea here is that longer focal lengths allow the subject to fill the frame while being further away from the camera. It's this increased distance between the subject and the image plane that tends to result in relative changes to the perspective of distance objects that appears to produce straighter lines, flatter shapes and less depth between the subject's features.

A lens's depth of field is basically the area it can keep in focus at a given distance. Setting the point of focus determines what area of the subject will be visibly sharp. Areas in front of and behind the POF will be out of focus. Placing the POF on key details and adjusting the width of the DOF will help guide the viewer's eyes to important areas in the image.

Since most real-time render systems don't simulate the complex physical limitations of optical systems, that determine the width of the DOF, there's no real benefit to discussing that particular topic in any depth. The DOF inputs can simply be adjusted until the final results look appealing.

As a final word of caution: an extremely narrow DOF can also cause issues with the perceived scale of an object. So it's often helpful to find some reference images of both snapshots and art photos to compare the minimum and maximum depth of field that's achievable at a given scale.

Camera angles are generally something that's more or less left up the individual artist's tastes. While there's a lot of different philosophies on the topic and a virtually endless loop of upcoming trends, there's always the risk that unconventional compositions will turn away most viewers who are just looking for traditional breakdown shots of in-game assets.

Since consistency and ease of viewing is important for most general portfolio projects it's often going to make sense to just use the traditional mix of three-quarters, front, side and back angles for the majority of the images. When it comes to thumbnails, leading covers and narrative images there's a lot more latitude for creative compositions. So having the right mix of creative and conventional camera angles should make for broader appeal.

One thing to be especially mindful of is that certain extreme low and high camera angles can make things appear out of scale. When combined with lens distortion this effect can produce some unique but often unrelatable results. There's a fine line between interesting and incomprehensible. So really take the time to work through several iterations of any unconventional camera angles and try to find the most visually appealing variant that still aligns with the stylistic goals for the project.

The multi point lighting setups used to author the textures were mostly bright, outdoor scenes with warm to neutral color casts. This type of lighting setup made it really easy to simulate a wide variety of environmental lighting conditions by turning individual lights on and off. After the textures were mostly completed, the final materials and textures were put through a series of lighting tests with a few different HDRI sky images and very basic single point lighting.

So coming up with idea for a very dark, high contrast two point lighting setup for the final renders was more the result of an iterative process of testing the textures than anything else. While testing the material separation between the details in the normal and roughness channels, the text details on the bottom cover really stood out when lit from behind with a single rim light.

This eventually lead to adjusting the rim light to become a strong key light and adding a softer fill light to the same side to pickup some of the details in the shadows. Additional lighting test started moving in a similar direction but with slightly deeper shadows and less rotational separation between the key and fill lights. A fairly strong highlight from the key light helps lift out the subtle details in the normal and roughness channels at different times and the softer fill light brings up the shadows just enough to expose the major shapes on the other side of the model.

Adding a strong rim light did help by adding some visual interest to some of the tests but due to the mix of flat and curved shapes on the model it often just got in the way and caused some really distracting highlights. So the final setup used for most of the renders is fundamentally a two point lighting system .Though a few of the renders do have supplemental kicker lights that are masked off so they only interact with a very small part of the model.

Standard zoom lenses can handle a wide range of situations but as a trade-off they also tend to have comparatively long minimum focal distances for relatively short focal lengths. Which can make it difficult to photograph small objects up close with these types of lenses. For small subjects and closeups of fine surface details it often makes sense to use a dedicated macro lens that has a short close focus distance and reasonably long focal length. This allows the lens to keep things in focus while getting reasonably close to the subject without introducing a lot of outwards distortion. Using a longer focal length like 100mm provides a bit of lens compression that will help fill the frame while also rendering the image circle with a perspective that keeps the linear elements fairly crisp.

Composition in the first image is pretty basic. Standard side view with a slight down angle. A strong key light comes in from the upper left side of the image, from behind the subject, to act as a partial rim light while obscuring the foreground elements with shadows. It's also positioned a bit lower than normal so picks up a lot of the minor surface imperfections with a wide highlight that rolls off into the base color of the paint.

The fill light is a bit softer and much lower. Almost completely parallel with the flat surface in the center of the image. It also has a slightly warmer color temperature that provides a bit of contrasting color that makes the surface a bit more interesting and easier to read. There's a lot of text on the back cover so the DOF is kept fairly thin and the focus point is set near the bottom of the frame to draw attention to that single line of text at the bottom.

Modified three-quarters front view with the camera placed slightly above and a slight downward tilt. Camera angle and lighting are both positioned to place a strong emphasis on the linear forms. Key light is in front of the subject and enters the frame from the top right. This creates strong highlights on the top of the shapes and partial shadows over some of the flatter areas that are empty.

Fill light matches the intensity of the key light and comes in from the left of the frame. The direct side lighting is slightly lower than the subject and points upwards to lift some of the shadows on the underside of the shapes. Overall the lighting setup for this image is a lot brighter since it needs to catch the details in the roughness textures. Focus point is kept towards the front of the hinge to draw attention to the paint chips, scratches and grime layers. DOF is still pretty thin since the recessed details on the top of the lid aren't that interesting when viewed from such a low angle.

Another modified three-quarters view that's slightly down and off to one side. Other version of this composition had a lower camera angle but this created a forced perspective that felt out of scale when shown along side the previous images. Key light is placed to the right side and slightly above, shining down to highlight the details in the normal textures. Shadows from the key light do obscure some of the empty space between the top and bottom half of the shapes to provide a visual rest and some additional depth.

A soft fill light shines from right to left. It's placed slightly above and behind the center line so it only catches a limited number of surfaces that are facing the right side of the frame. There's also an orange kicker light that's shining up from almost directly below. This helps catch some of the subtle shape transitions around the bottom edges and provides a nice boost to the color in the worn brass parts.

Point of focus is still very close to the edge of the object but the way it's rotated means more of the shapes towards the front are in focus. Since there's lots of repetitive details on this side the DOF is still fairly shallow to keep the attention focused on the details closet to the camera.

More conventional high angle three-quarters view that's slightly rotated more towards one side to match the previous composition. A fairly strong key light comes in from the upper left side of the image. Placed further in the background this key light rakes across the surface at a slightly lower height with a slight downward tilt to highlight the details in both the normal and roughness textures.

The softer fill light shines down from the upper right side of the image and highlights details in the roughness channel as it wraps around the curves on this side of the subject. There's also a kicker light that comes in from the middle left side of the image and shines towards the right side to simulate a light bounce from the fill light. This additional lighting detail is just there to help lift some of the darker shadows on the left side of the image and makes it a bit easier to read the shapes. Deeper DOF shows off a bit more of the detail on the top cover and the focus is more towards the middle of the image.

A direct top down view makes the text on the dial and ruler is easier to read. Rotating the top cover up slightly helps fit more of the subject in the frame and also provides an opportunity to shape the light with the opening in the center. The strong key light shines down from the top of the frame and has a slightly weaker kicker light that simulates a bounce from the fill light. This supplemental lighting effect helps lift the values along the top edge of the ruler so a consistent highlight is visible across the base that's laying flat and the top cover that's tilted upwards.

Bright fill light is placed on the right side of the image and shines across the flat areas along the top of the base. There's an additional kicker light that's shining through the slot and down onto the bezel. When it comes to replicating complex studio lighting setups in real-time engines it sometimes makes sense to do thing the easy way. Technically this setup uses four lights: key, fill and two kickers but it could be done using just the key and fill but adding additional mesh objects to act like bounces and flags would take a lot more time and effort than just adding a couple extra lights and masking them in post.

Wider DOF in this composition is needed to handle the increased surface depth caused by rotating the cover up towards the camera. Focus point is somewhere between the text on the dial and the text on the ruler. This setup uses a background focus where the closer something is the softer it appears to be as it enters the out-of-focus zone while everything behind the POF remains relatively sharp.

There's definitely some risk in opening with more abstract camera angles and high contrast lighting setups. This is just a quick example of what a more conventional set of camera angles would look like with this particular lighting setup. Not the most interesting composition but it does provide a decent overview of the model and textures. Which is probably what a lot of people care about more than anything else. Very similar lighting setup to the previous five images but the camera angles make for a very different type of presentation.

This comparison of the low-key two point lighting setup and a more conventional three point lighting setup illustrates just how much the lighting can influence how the model and textures are perceived. Under normal lighting conditions the more subtle surface details won't be visible unless the lighting hits just right.

That's where there's certain trade-offs in terms of just how far to push the lighting and composition. Too bland and it's just not all that compelling. Too intense and it becomes unrelatable. So a large part of the challenge of creating unique portfolio renders is balancing what the audience expects to see with the artistic vision for the piece.

For portfolio renders, where the goal is to show off as much of the work as quickly as possible, it's hard to beat a standard 3 point lighting setup with DOF turned off. That way everything is evenly lit and clearly visible. While it may not be the most exciting approach to lighting a scene it does provide a certain level of consistency while also putting the modeling and texturing skills that went into creating the asset front and center.