Dev Blog: Physically Based Rendering and Post Effects

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rise_of_the_tomb_raider_Dev_Blog_Physically_Based_Rendering_and_Post_Effects

Mike Oliver, Technical Art Director

One of the main goals in Rise of the Tomb Raider is to create rich, believable environments that are grounded in reality. Environments where players feel connected with Lara and her journey on a personal level. This is a very difficult challenge because of the limitations of a game environment and the constantly evolving world. Physically Based Rendering and Post Effects greatly help solve this visual challenge.  

Physically Based Rendering is a relatively new technique to video games but has been extensively used in film production for many years. It allows artists to accurately simulate real-world materials and lighting conditions. Surfaces accurately reflect and refract light based on their absorption and diffusion properties. Essentially, they look and behave more realistically and naturally. Lighting is achieved through the use of images that simulate real lighting conditions. These techniques, when combined, contribute heavily to creating believable and realistic environments.

Post effects also play another important role in creating the believable world. They are filters that are applied to the world and provide the final level of polish and cohesiveness. 

Read on for a breakdown of commonly used techniques and effects in Rise of the Tomb Raider

Image Based Lighting

Image Based Lighting is a technique where light information is stored in a texture, called a probe. Probes project this light information into the surrounding area, simulating realistic lighting conditions. Below is an example of a room lit with a single directional light (left) and the same room with an applied light probe (right). This technique provides artists the flexibility to create their scenes with significantly less lights, while offering greatly increased flexibility and quality.

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Physically Based Materials

In order to take advantage of the new image based lighting model used in Rise of the Tomb Raider we also improved our material pipeline to support Physically Based Materials. Physically based materials allow for more accurate and natural looking surfaces that retain their quality in a variety of lighting conditions. These materials are comprised of 3 parts. Albedo, roughness, and reflectance. Albedo defines the colour intensity of a surface. Reflectance defines the metallic properties of a surface, and roughness defines how much of the reflected light is scattered.  

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Post FX

In addition to our PBR workflow we added and improved a number of post process effects. Post process effects are the final touches that artists apply to a scene to help bring all the elements together. They represent a significant portion of the look and feel of Rise of the Tomb Raider.

Colour Grading

Colour grading is a post effect used substantially throughout Rise of theTomb Raider. Colour grading allows artists to make adjustments to the final rendered image such as brightness, saturation, contrast and colour remapping. This is achieved through the use of a ‘look up table’ (LUT). A LUT is represented as a 256 x 16 texture that contains all the colour adjustment information. It is a very powerful feature in Rise of the Tomb Raider because it is the final polish that reinforces the mood, storytelling and emotional state of a level.

Below are a few variations of what can be achieved using colour grading. The Base LUT is a raw render from the game with no colour grading applied.  Final is the LUT currently being used in this particular level.  Warm and Fantasy LUT’s are just further examples of how you can easily change the tone and mood of a space.

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Adaptive Tone Mapping

Adaptive Tone Mapping is another feature in modern video games that was introduced because of Physically Based Rendering. Scenes are now lit in High Dynamic Range (HDR), essentially meaning they can be extremely bright. 

Televisions, like our eyes, are unable to visualize this light range without making adjustments. Adaptive Tone Mapping automatically converts this extreme range of light into a range that monitors can display. In Rise of the Tomb Raider, this is best represented by the brightness shift while walking from a dark space into a bright area. It behaves just as your eyes naturally would, by dilating.

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Screen Space Ambient Occlusion

Ambient Occlusion is a rendering technique used to calculate how much a surface is affected by ambient light. Areas that are less affected appear darker or shadowed. In the world of Rise of the Tomb Raider, Ambient Occlusion plays a very critical role because it helps integrate objects with their surroundings and makes them feel grounded in reality.

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Motion Blur

Motion Blur is a post effect used frequently in Rise of the Tomb Raider. Because a large portion of our gameplay focuses on exploration and traversal we used motion blur to help create a believable environment by providing a sense of speed, fluidity, and cohesiveness.

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Depth of Field

Depth of Field is the range between a near and far point that appears in focus. In Rise of the Tomb Raider we used depth of field to separate foreground and background elements as well as draw the attention of the player to key areas.

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Screen space reflections

Screen space reflections are another new feature added in Rise of the Tomb Raider. They are a cost effective way of reflecting the environment which helps to integrate Lara into her surroundings and create a believable world.

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Screen Glare

Screen glare is a subtle feature we use extensively throughout the game. It represents the grunge on the lens of a camera that is captured during various lighting conditions, usually consisting of small dust particulates or drops of moisture. We use this technique to enhance the overall atmosphere and feeling of  Rise of the Tomb Raider.

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Volumetric Lighting

Volumetric Lighting is a 3D effect that simulates beams of light in an environment, such as light passing through a window. It helps create a believable atmosphere that the character can interact with. Additionally it is an excellent story telling mechanism that is used to direct the player to locations of interest

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Mike Oliver
Technical Art Director, Rise of the Tomb Raider