Light Tracer Render 2.0

Light Tracer Render
7 min readOct 29, 2021

We are proud to announce Light Tracer Render 2.0 (, both Native and Web versions!

Thanks to our users' support and feedback we were able to actively develop Light Tracer during the past year. We sincerely appreciate your insight because it helps us build a better product for everyone. To express our gratitude we have decided to provide this huge upgrade for free for all Light Tracer users who purchased subscriptions or perpetual licenses for previous versions!

This release took a bit longer than usual, and the reason is that we have packed in a lot more new content and features that take your visuals to the next level. We invite you to take a look at the changelog and see what’s new.

Caustic Mode / Path Guiding

Some 3D scenes encountered in product visualization, automotive industry, architectural visualization, and jewelry design often cannot be efficiently rendered with the conventional path tracing, leading to significant render times. For such cases, we have developed a new Path guiding technique that uses online learning to guide light paths during rendering based on an estimate of incoming radiance. Path guiding can make the convergence faster than unaltered path tracing in complex light transport phenomena, such as caustics. This is why we called it Caustic mode, although it can be useful for other scenes with a predominance of indirect illumination. In the video below, you may see how the caustics scene is rendered with conventional path tracing and Caustic mode:

Rendering using conventional path tracing and “Caustic mode

The good news for Light Tracer users is that this new mode does not require tuning any new parameters. Just turn it on in case conventional path tracing converges slowly.

Caustic mode” can be activated with the shortcut button on the toolbar

The only reason this mode is not enabled by default is its high computational complexity. It actively loads not only the GPU but also the CPU for processing statistics continuously received from the GPU. Therefore, for simple and well-lit scenes, which are already effectively handled by conventional path tracing, its use is impractical.

Transparent Shadows

For collecting direct illumination at each surface point, one or more shadow rays are cast to the light sources. In conventional path tracing, if a shadow ray hits an occluder object (even a glass window), a corresponding surface point is in shadow. The surface can still receive light through indirect illumination, but it is much more difficult to calculate, resulting in higher noise levels and longer rendering time. That is why path tracing can easily handle the directly illuminated outdoor scenes but struggles with the indirectly lit interiors.

To address this issue, the new release introduces a Transparent shadows technique. If shadow rays hit semi-opaque objects, they will be attenuated and keep traversing until they either encounter an opaque object on their way to the light or reach the light itself. That allows to dramatically increase the convergence in situations when the light is coming through the glass windows (interior scenes) or surfaces those transparency specified using alpha-map (vegetation, tree foliage, grass).

To demonstrate the improvement, let us showcase the render of a Minecraft-style scene that widely uses alpha-map transparency:

Light can pass through transparent textures, so there are no artifacts and dark areas

Another good example is rendering the interior of a car, which is now possible at almost the same speed as rendering the exterior:

Rendering of a car interior visible and illuminated through glass windows

Mesh emitters

With Light Tracer Render, any mesh can be turned into an emitter (“mesh light”) where the triangles making up the surface act as a large collection of emitters. The improved ray tracing engine now performs direct sampling of arbitrarily defined mesh lights. That significantly reduces the shading noise and is especially useful when rendering architectural and interior scenes.

Rendering of the scene illuminated with mesh emitters

More importantly, mesh lights will be effectively processed even when obscured by (semi-) transparent objects (such as lampshades, car headlight glass, etc.). That is possible thanks to the Transparent shadows technique presented above.

IES profiles

Along with efficient light sampling, the fresh release introduces support for IES profiles used to describe the angular distribution of the emitting light. It is particularly useful when the light source is partially covered and/or some lensing occurs. The light distribution would “bake” the complex occlusion and lensing phenomena allowing for faster rendering. As a result, it is possible to create a light setup that might show how the lights will look in reality, which is especially important for architectural visualization.

Light Tracer Render supports industry-standard files in a format called IES. In this file, we can find the physical properties of a lamp, all ready to be used in rendering. Just attach the IES file to the new IES profile slot like any other texture:

IES file can be inserted into the new “IES profile” slot

The IES profile can be attached to any mesh light. However, it is wise to set it for small sources modeled as a disk or rectangle. Below, you find interior rendering produced in Light Trace Render 2.0:

Rendering interior scene with IES profiles specified

Physically-based dielectric coat

The coating model was reworked, and as a result, the previously available clearcoat model was replaced with a physically correct layered model. That allows modeling custom materials like car paint, glazed metal, lacquered wood, and ceramics.

Metallic car paint with dielectric coating

The coating layer can be optionally tinted (filled with an absorbing media). In such a case, the coating will account for the directionally dependent absorption within the varnish layer. Another important application of the coating is plausible modeling of thin transparent objects like glass windows, glassware, car headlights, etc.

New shadow catcher

Shadow сatcher is crucial for the product rendering, so we put a lot of attention into improving it. Also, a new Reflection catcher is now available that captures glossy reflections of the scene. With both catchers, you are able to use any background or keep it transparent, so you may easily drop the render into slides or on the website.

Shadow (left) and glossy reflection (right) catchers

Other improvements

Numerous additional improvements have been made to the ray tracing engine and UI. Notable examples include:

Geometry builder / Extended floors

Light Tracer now provides a Modeling widget that makes it easy to add primitives to the 3D scene. Primitives can be added either by mouse click or using drag-and-drop. In particular, such primitives are useful for adding light sources to the scene.

Along with this, the fresh release offers an extended set of scene floors/stands that will help you quickly and easily create the environment for a nice shot.

Revised texture slots

The texture slots UI has been significantly improved. In addition to better usability, a new IES profile slot has been added into the Emission section, as well as an Opacity slot allowing explicit management of transparency map.

Camera slots

The new version has got support for Camera slots. Now you can quickly switch between different views for easy scene setup. The camera slot stores not only the view itself but also the lens and depth of field settings.

Hide objects to the camera

The fresh release introduces a new object visibility state. Now an object can be hidden only from the camera, but not excluded from the scene. As a result, the object itself is no longer visible in the render, but its impact on scene illumination still remains. For example, in this way, you may hide the mesh light source, but it will continue to illuminate the scene or hide the ceiling in the room to render a top view.

We need your feedback!

You are welcome to a free 14-day trial period without any restrictions in functionality and watermarks. Get it right now at!

Committed to our users, we’ve been working hard on this release, and so we welcome your feedback! Let us know about your experience! Help us improve by sharing in our Discord community.

3D models used:
— Porsche 911 Carrera 4S by Karol Miklas
— LuxCoreRender caustic test by dade916
— Forest demo
patrix (
— Interior scene by Allay Design
— Honda E (Detailed Interior) 2021 by Xlay3D
Wankel pendant by Hans de Ridder (



Light Tracer Render

Light Tracer Render is an easy to use tool for photorealistic rendering. It works in browser and have a native version. It’s fast and works on any GPU!