What Is Ray Tracing? Light, Shadows and Reflections in Games
Ray tracing explained for PC players: how games follow rays of light, what changes on screen, why it costs frame rate and when the setting is worth turning on.
Open the graphics menu of almost any recent PC game and a switch labelled ray tracing sits somewhere near the top, often with its own sub-menu of options. Flip it on and the scene changes in ways that are sometimes dramatic and sometimes hard to spot, while the frame counter usually drops. This guide explains what the technique actually does, why it is so demanding and how to decide whether it belongs in your settings.
The short answer
Ray tracing is a way of drawing a 3D scene by simulating the paths that light takes. The renderer sends out rays from the camera, works out what each ray hits, and then asks follow-up questions: is this point in shadow, does the surface reflect something else, how much light bounces in from nearby walls? The answers decide the colour of each pixel.
Film studios have used the approach for decades because it produces convincing light. Games avoided it for a long time because every frame has to be finished in a small fraction of a second, and tracing millions of rays per frame was simply too slow for consumer hardware.
How games drew light before
The traditional method is called rasterisation. Instead of following light, the graphics card projects every triangle in the scene onto the screen and colours the pixels it covers. It is extremely fast, but it knows nothing about what lies off screen or behind an object. Developers fill that gap with clever approximations:
- Shadow maps, which render the scene from a light's point of view to guess what sits in shade.
- Screen-space reflections, which mirror only what is already visible, so reflections vanish when the source moves out of view.
- Baked lighting, calculated in advance and stored with the level, which looks lovely until something in the room moves.
These tricks are the reason older games can look superb on modest hardware. They are also the reason a puddle sometimes fails to reflect a passing car, or a character's shadow looks oddly soft.
What ray tracing changes on screen
Most games do not trace the whole image. They keep rasterisation for the basic picture and use rays for specific effects, which is why the settings menu often lists them separately.
Reflections
Ray-traced reflections can show objects that are off screen or behind the camera. Shop windows, wet streets and polished floors are where the difference stands out most.
Shadows
Shadows sharpen near the object that casts them and soften as they stretch away, the way they do in daylight. Several overlapping lights produce believable overlapping shadows.
Global illumination and ambient occlusion
Light bouncing off a red wall tints the floor beside it, and corners darken naturally where little light reaches. This is often the most transformative effect, because it changes the mood of an entire room rather than one surface.
Some titles go further and apply what is sometimes called path tracing, where nearly all lighting comes from traced rays. The results can look striking, and the hardware demands rise sharply.
Why it costs frame rate
Every effect needs extra rays, and every ray has to be tested against the scene's geometry. Modern graphics cards include dedicated hardware for those tests, but the work still competes with everything else the card does in a frame. That is why switching ray tracing on usually lowers the frame rate, and why the drop varies so much from one game to another: a title with one subtle effect asks for far less than one that traces reflections, shadows and bounce light together.
Games also trace far fewer rays than a film renderer would, then clean up the grainy result with a denoiser. When that clean-up struggles, you may notice smearing on moving objects or a faint shimmer on reflections.
Upscaling: the usual partner
Because ray tracing is so heavy, it is commonly paired with upscaling, which renders the game at a lower resolution and rebuilds a sharper image for your display. Our explainer on DLSS and other upscalers covers how that works and what to watch for. Many players find the combination the only practical way to enjoy ray-traced effects at a smooth frame rate.
Should you turn it on?
There is no universal answer, but a few questions help:
- What kind of game is it? Slow, atmospheric games with lots of glass, water and indoor lighting benefit most. Fast competitive shooters usually reward a high, steady frame rate instead.
- Does your card support it in hardware? Check the requirements listed on the game's store page and your graphics card's specifications.
- Which single effect matters most? Try turning on only reflections or only global illumination. One effect often delivers most of the visual gain at a fraction of the cost.
- Does it feel smooth? Judge with a controller or mouse in hand, not from screenshots. If movement feels sluggish, step back a level.
Ray tracing is not a pass-or-fail feature. It is a set of dials, and the best setting is the one that makes the game look better without making it feel worse. If you are still assembling the rest of your setup, our roundup of gadgets PC gamers like to have covers the accessories around the screen.
