Introduction
Ray tracing has become an increasingly popular rendering technique in recent years, especially for animated films. But is it truly a viable solution compared to rasterization? In this article, I will examine the pros and cons of ray tracing for animated films to determine if it is a rendering technique that is here to stay.
What is Ray Tracing?
Ray tracing is a rendering technique that traces the path of light rays as they interact with objects in a 3D scene. It simulates the physical behavior of light to create highly realistic lighting, shadows, reflections and refractions.
Here’s a quick overview of how it works:
- Rays are emitted from the camera into the 3D scene
- When a ray hits an object, additional rays may spawn like reflection, refraction and shadow rays
- The rays are traced recursively as they interact with objects, simulating real light behavior
- The rays ultimately hit light sources, allowing light and color values to be calculated
- The final image is computed by combining the light values of all rays
The end result is photo-realistic rendering with accurate lighting and lifelike materials. Ray tracing solves many of the limitations of rasterization methods used in traditional rendering.
Benefits of Ray Tracing
Here are some of the main advantages of using ray tracing for animated films:
Realistic Lighting and Shadows
Ray tracing excelmodels at creating soft, natural lighting and shadows. Light sources like the sun or bulbs emit rays that can bounce around a scene just like in real life. This gives artists much more control over lighting mood and intensity.
Subtle effects like light bleeding and colored bounces are also possible. Ray traced shadows have natural penumbras and smooth edges, avoiding the jagged aliarasing seen in rasterized shadows.
Accurate Reflections and Refractions
Smooth reflective and transparent materials are very difficult to render correctly with rasterization. But ray tracing handles them perfectly by accurately tracing reflection and refraction rays.
Ray traced reflections and refractions have the proper perspective, intensity and distortion as rays bend when passing through different mediums. This allows highly realistic materials like glass, water and metals.
Detailed Ambient Occlusion
Ambient occlusion adds contact shadows where two surfaces meet, adding depth and realism to a scene. Ray tracing calculates ambient occlusion by tracing rays in all directions from a shaded point.
The result is a smooth and detailed ambient occlusion pass that brings out all the subtle crevices and contours of intricate 3D models. Rasterized ambient occlusion lacks this level of accuracy.
Unified Rendering Pipeline
With ray tracing, lighting, shadows, reflections and global illumination can be handled by the same universal workflow. Artists don’t have to composite multiple rendered passes or use “cheat” techniques.
This unified rendering pipeline is intuitive and makes iterative improvements much faster. Ray tracing streamlines the entire rendering process for animated films.
Challenges of Ray Tracing
However, there are some significant downsides to ray tracing that need to be considered:
Rendering Speed
Ray tracing is incredibly computationally intensive. Each pixel requires tracing many rays through the scene as they bounce around interacting with objects.
Render times can be orders of magnitude slower compared to rasterization. This can become highly problematic for animated films where frames need to be rendered quickly. Often complex optimizations are required to make ray tracing feasible.
Memory Usage
In addition to rendering times, ray tracing also requires far more memory than rasterization. All of the scene data needs to be accessible to calculate ray intersections and lighting.
For complex animated films with detailed models and environments, the memory overhead of ray tracing can be substantial.
Difficult Lighting and Material Setup
While ray tracing makes some aspects of lighting easier, in other ways it is far more difficult. Light sources, material shaders and scene properties need very fine tuning to get appealing visual results.
It takes significant skill and experience to light and craft materials optimally for ray tracing. This can lengthen development time for films using the technique.
Limited Flexibility for Stylization
The highly realistic nature of ray tracing makes it best suited for photorealistic rendering. It is far more difficult to use ray tracing for non-photorealistic or stylized animation.
Rasterization offers more flexibility for creating exaggerated shapes, outlines and unlimited art styles that may be needed for many animated films.
Ray Tracing in Animated Feature Films
Despite the challenges, ray tracing has been making inroads into animated features. Here are some examples:
Cars 2
In 2011, Pixar’s Cars 2 became the first animated film to use ray tracing for car materials and environments. This added tremendous realism to the shiny car paint and reflective surfaces.
Frozen
Disney’s Frozen extensively used ray traced environments to build the icy world of Arendelle. Ray tracing provided high accuracy for refracting and dispersing light through frozen ice and snow.
Spies in Disguise
For the spy gadgets in Spies in Disguise, the developers ray traced reflective and metallic surfaces to bring them to life realistically. Ray tracing provided the accuracy needed.
The Mitchells vs. The Machines
Sony Pictures Animation’s film The Mitchells vs. The Machines contained extensive ray traced lighting, reflections and refractions throughout. The team found ray tracing crucial for rendering the robot’s shiny metallic materials.
These examples illustrate that ray tracing can definitely provide significant benefits for certain aspects of animated films where accuracy is critical. The challenges can be mitigated by using it selectively and integrating it into existing rasterized pipelines.
Conclusion
Ray tracing brings unmatched realism and accuracy to animated films when used properly. For photorealistic rendering and specific material types, it can be a game changer. However, rasterization still excels at performance and flexibility for stylized films.
The answer seems to be integrating ray tracing carefully into existing workflows. Used selectively where it provides the most impact, ray tracing can be a viable solution for animated film rendering as evidenced by major productions already leveraging it.
With rendering algorithms and hardware improving rapidly, ray tracing has an exciting future ahead in animation. Artists are just beginning to tap into its potential for crafting innovative animated stories. We can expect ray tracing to become an indispensable part of an animator’s toolkit in the coming years.
