What Is Ray Tracing and How Does It Work?

Ray tracing stands as the most significant technical leap in computer graphics rendering of the last decade. It moves the medium from simply approximating reality to accurately simulating it.

While traditional methods rely on artistic tricks to fake lighting, ray tracing follows the physics of the real world. In plain English, it is a technique that creates an image by tracing the path of light as pixels in an image plane and simulating the effects of its encounters with virtual objects.

This process results in lifelike reflections and shadows that flat images cannot replicate.

The Mechanics of Light Simulation

Ray tracing changes how computers render 3D scenes by prioritizing physics over artistic approximation. To achieve photorealism, the software must perform complex calculations that mimic how light behaves in the physical world.

However, the computational approach is often the exact opposite of what happens in nature to ensure the process remains efficient enough for real-time applications.

Reverse Engineering Nature

In the physical world, a light source emits billions of photons. These particles bounce off objects and eventually hit the retina of your eye to form an image.

Simulating every single photon that leaves a light bulb would waste immense processing power since most of them never hit the viewer. Computer graphics solve this by reversing the process.

The engine traces rays from the “camera” or eye view back into the scene. It only calculates the light paths that actually contribute to the final pixels visible on the screen.

The Path of the Ray

The process begins with the Primary Ray. This line creates a trajectory from the camera lens through a specific pixel on the screen until it collides with a virtual object.

This collision point is known as the Intersection. Once the software identifies exactly where the ray hits a 3D model, it calculates the next step.

The ray might stop if the object blocks it, or it might generate Secondary Rays. These subsequent lines determine if the light reflects off a surface, refracts through transparent material, or travels toward a light source to determine shadow placement.

Material Interaction

When a ray intersects with an object, it does more than simply hit a geometric shape. It queries the data assigned to that specific point on the 3D model to determine what it touched.

Modern rendering engines use materials that contain detailed information about surface properties. The ray reads values for roughness, metalness, and color.

If the surface is rough like dry asphalt, the ray scatters to create a dull or matte appearance. If the surface is smooth and metallic, the ray bounces at a perfect angle to generate a sharp reflection.

This data exchange dictates exactly what color the final pixel should display.

Rasterization vs. Ray Tracing

For decades, the graphics industry relied on a specific technique to render 3D environments efficiently. While ray tracing represents the new standard for realism, the vast majority of digital content created over the last thirty years utilized a method called rasterization.

This approach prioritizes speed and performance, allowing hardware to generate complex scenes at high frame rates without the immense computational cost of simulating actual physics.

Rasterization: The Traditional Method

Rasterization works by converting three-dimensional models into two-dimensional images. Virtual objects are built from a mesh of triangles or polygons.

The computer takes these 3D shapes and projects them onto a flat plane, effectively flattening the data into the colored pixels displayed on a monitor. Since this process does not inherently calculate how light behaves, developers employ clever workarounds to simulate depth.

Techniques like shadow maps and baked lighting are pre-calculated and painted onto the objects. These static effects trick the eye into seeing realistic lighting without requiring the computer to solve complex light physics in real time.

The Fundamental Difference

The primary distinction between these two technologies is simulation versus approximation. Rasterization essentially guesses where light should be based on parameters defined by an artist.

It is an efficient estimation limited by what creators manually place in a scene. Ray tracing calculates where light actually is.

It treats light as a physical entity that interacts dynamically with the environment. Consequently, visuals are determined by mathematical interactions and material properties rather than pre-drawn illusions.

Hybrid Rendering

Running a game entirely with ray tracing places an immense strain on hardware. To manage this, modern developers often utilize a hybrid rendering pipeline.

The game engine uses rasterization to draw the main geometry and textures, which ensures the frame rate remains high and stable. It then applies ray tracing selectively for specific elements that benefit most from accuracy, such as reflections in a puddle or complex shadows.

This strategy balances performance with visual fidelity to offer high-quality graphics on current hardware.

The Three Pillars of Visual Enhancement

When you enable ray tracing settings in a game or application, the visual improvement usually stems from three specific areas. These features work together to ground objects in their environment and remove the artificial look that often plagues computer-generated imagery.

While high-resolution textures make surfaces look detailed, accurate light behavior is what makes them look real.

Reflections

Traditional rendering relies on a technique known as Screen Space Reflections. This method has a significant limitation because it can only reflect objects that are currently visible within the camera frame.

If a player looks at a mirror or a shiny car hood, the reflection will disappear or distort if the object being reflected moves off-screen. Ray tracing solves this issue entirely.

Since the computer simulates the path of light rays rather than just copying pixels from the screen, surfaces can accurately reflect objects located behind the camera, above the player, or even around corners. This capability maintains visual consistency regardless of where the player looks.

Shadows and Ambient Occlusion

Standard graphics often struggle to replicate the nuance of shadows, frequently rendering them with uniformly hard or blurry edges. Ray tracing introduces a phenomenon called contact hardening.

A shadow appears sharp and defined right where it touches the object casting it, but it naturally softens and diffuses as it stretches further away from the source. Beyond cast shadows, the technology also improves ambient occlusion.

This refers to the subtle darkening that occurs in cracks, corners, and crevices where light struggles to penetrate. Ray tracing calculates exactly how much light is blocked in these tight spaces to create deep and realistic shading rather than a generic dark outline.

Global Illumination (GI)

Global Illumination represents the most subtle but impactful effect on scene realism. It handles indirect lighting, which mimics how light bounces from one surface to another.

For example, if bright sunlight hits a red wall, the light bounces off that surface and tints the adjacent floor with a soft red hue. This is known as color bleeding.

Furthermore, global illumination manages diffuse illumination to fill a room with light naturally. In the past, artists had to manually place invisible light sources to brighten dark corners.

With ray tracing, the light propagates through the virtual space on its own to create a cohesive and naturally lit environment.

Hardware Requirements and Compatibility

Implementing ray tracing requires more than just a software update or a new game engine. The process demands a fundamental shift in computer architecture.

Because the technology relies on simulating physical interactions rather than simple projection, it places a unique and heavy load on the system. Consequently, running these advanced visuals necessitates hardware that is specifically engineered to handle the math involved.

The Computational Heavy Lifting

Standard graphics cards struggled to perform ray tracing for decades because they were not built for the task. Traditional GPUs are excellent at rasterization, which involves pushing millions of pixels onto a screen very quickly.

However, calculating light paths is a different type of workload. It requires the system to compute the intersection of millions of rays with thousands of geometric shapes every second. This volume of mathematical operations overwhelmed older processors.

Without specialized support, the sheer number of calculations would cause the frame rate to drop to unplayable levels.

Dedicated Hardware

To make real-time ray tracing viable, manufacturers introduced specialized silicon directly onto the graphics chip. Nvidia developed RT Cores, while AMD introduced Ray Accelerators.

These are dedicated processing units designed with the sole purpose of calculating ray intersections and bounding volume hierarchies. By offloading the heavy math of light simulation to these specific cores, the rest of the graphics card is left free to handle standard rendering tasks like texturing and shading.

This parallel processing allows the system to generate realistic lighting without choking the overall performance.

Platform Availability

Access to this technology is currently defined by the generation of the hardware. On the PC front, support is found in Nvidia's RTX series and AMD's Radeon RX 6000 and 7000 series cards.

These components generally offer the highest performance ceiling and visual fidelity. In the console market, the PlayStation 5 and Xbox Series X/S are equipped with the necessary architecture to support ray tracing.

However, consoles often operate within stricter thermal and power limits. As a result, they may use a more limited implementation of the technology compared to a top-tier desktop computer.

Performance Costs and Optimization

Ray tracing delivers incredible visuals, but those improvements come at a significant price. Turning these features on places a massive demand on system resources.

Consequently, users often face a difficult trade-off between fluid motion and realistic lighting. To bridge this gap, engineers rely on clever software techniques that maintain high image quality without sacrificing the speed required for a smooth experience.

The Frame Rate Tax

The most immediate side effect of enabling ray tracing is a sharp drop in performance. Calculating complex light physics in real time is computationally expensive.

Even with powerful, modern hardware, the sheer volume of math required can cause the frame rate to plummet. In many cases, a game running smoothly at 100 frames per second might drop to half that speed once these lighting effects are active.

This performance penalty is often referred to as a “tax,” and it is the primary reason many users hesitate to enable the feature during fast-paced gameplay.

The Noise Problem

Computers cannot simulate every single photon in a scene, as the calculation would take too long. To keep the process manageable, the engine traces a limited number of rays per pixel.

This creates gaps in the data, resulting in an image that looks grainy or speckled, similar to a photograph taken in low light. This visual artifact is known as noise.

To fix this, rendering engines apply denoising filters. These algorithms analyze the image to fill in the missing information and smooth out the grain, producing a clean and crisp final picture.

AI Upscaling as the Solution

The most effective way to combat performance loss is through AI upscaling technologies like Nvidia’s DLSS or AMD’s FSR. These tools allow the graphics card to render the game at a lower internal resolution, such as 1080p, which is much easier and faster to process.

Then, artificial intelligence algorithms analyze the frame and reconstruct it to look like a sharp 4K image. This process drastically reduces the workload on the GPU.

It allows players to enjoy the advanced lighting of ray tracing while reclaiming the smooth frame rates they initially lost.

Conclusion

Ray tracing represents a massive shift in how computers generate images. It trades the raw speed of traditional methods for physical accuracy to turn a convincing painting into a simulation of the real world.

While enabling these features requires expensive hardware and often reduces the frame rate, the technology delivers a level of depth and immersion that was previously impossible. It transforms flat environments into spaces that feel inhabited and tangible.

Currently, ray tracing acts as a premium feature or a hybrid option used alongside older techniques. Yet, it is effectively the inevitable destination for computer graphics. As hardware becomes more powerful and optimization tools mature, the reliance on rasterization will fade.

This technology is not merely a passing trend. It is the new foundation for the future of digital rendering.