Tutorial: Jewelry rendering

Tutorial demonstrating a basic Jewelry Rendering in Light Tracer Render

The techniques you'll learn in this tutorial are fundamental to creating high-quality jewelry 3D visualization in Light Tracer Render. While basic principles are similar to other 3D product visualization, the particular challenge with jewelry rendering is that metal is fully specular (meaning it reflects like a mirror), and the gemstones are highly refractive. As a result, these objects virtually do not have their own color, and their appearance depends entirely on lighting and the environment. So, we have to ensure enough contrast and light in our 3D scene to make the jewelry attractive.

Import 3D model

A good visual starts with a good model. We have downloaded a great work by Radovan G. from GrabCAD. Most jewelry models are designed in CAD tools and are available in formats, such as 3DM, STEP, IGS. All these formats are natively supported by the native version of Light Tracer, so you may just drag the downloaded 3DM file on the app window:

Compose 3D scene

Now let's add a base for our model so that it doesn't hang in the air. In Light Tracer, you may create different floors and stands, from which we will choose a simple rectangular floor:

By default, the newly created rectangular floor gets shadow catcher material. A shadow catcher is a specific material, which is invisible to the camera but capable of receiving shadows from lighting in the scene. This is useful if we want to have a 3D object added on top of a photo or background.

Let's also duplicate the entire ring using the Scene Explorer, and place it on the floor next to the first ring to create a more interesting scene. For positioning scene objects, you may use a 3D manipulator and Transform widget described in the Basic UI tutorial.

Setup lighting and materials

For photorealistic 3D jewelry rendering, it is better to use high-contrast HDRI maps with neutral lights. A clear sky map provides good contrast, but it will give a blue tint to the frame and diamonds, which is highly undesirable. On the other hand, soft indoor lighting or cloudy skies will prevent a "fire" effect on the diamond. A diamond's “fire” is produced when white light disperses into rainbow colors when it hits its facets (the angled cuts in the stone). A lot of free HDRI maps can be found on polyhaven.com. We have used Autoshop map which has neutral lights and medium contrast. Go to the Environment tab, click on the Manage map button, and then on the Load map button to open the downloaded HDRI file. Note that you can make lighting smoother by blurring the HDRI map: click the Manage mapBlur map button and set the number of blurring steps (more steps – more blur).

Now let's assign materials to scene objects. Go to the Library tab and drag the appropriate presets onto the scene objects. For example, gold preset can be found under the Metal filter:

You can also enter the name of the desired material or part of it (for example, "gold" or "go") to filter out the presets. The diamond preset can be found under the Glass filter (or just type "diamond", “dia” in the filter text box). To make the scene more interesting, let's make one of the stones colored by setting the parameters in the Attenuation section of the Properties tab.

For example, you can set the green color and adjust absorption using the Density parameter. Natural-color green diamonds are very rare and one of the most valuable. After all the above settings, we got the following result:

Adjust rendering settings

In order for diamonds look right it is better to choose “Quality” preset on the Rendering tab. Alternatively, you may adjust settings manually. First of all, set the Max bounces parameter (maximum number of light bounces) that to 20-30 bounces. For scenes with complex indirect lighting and caustics, the Power clamp parameter is also important, which is responsible for the maximum light energy that a single ray can bring to the image. For plausible results, you need to set it to 300-500 or more.

Set depth-of-field

For the realistic rendering of diamonds, it is crucial to use the physical camera model with proper depth-of-field. The point is that if the ray of dispersed light is shorter than the width of the pupil of the eye (or lens aperture), the light is recombined and perceived as white light, which is light made up of all of the colors together. So, a pinhole camera (with zero aperture) produces unrealistically high dispersion. Our goal is to adjust the camera's f/stops just right to get a result similar to the human's eye. To get the idea, compare two pictures generated with pinhole and physical camera models:

You can switch to the physical camera on the View tab by selecting Depth of Field mode:

Below the Depth of Field button, you will see one input field and three round buttons.

The input field sets the lens f-number, which determines the depth of field. The larger the f-number, the greater the depth of field.

The first button turns on/off the autofocus mode. If autofocus is on, the camera will focus automatically on subjects in the center of the frame. If you click this button, you can manually pick the object on which you want to focus. Clicking this button again will return to autofocus mode.

The second button enables automatic adjustment of camera parameters for optimal depth of field. In this mode, the appropriate sensor size and focal length of the lens are adapted to the scene size. You only need to choose the f-number. By turning the auto-adjustment off, you can manually set all camera parameters.

The third button enables the 3x3 grid displayed over the frame for a more convenient composition.

Adjust backplate…

Backplates are really fairly straightforward. Check out the Environment tab, where you will see three options. The first option is None, which allows you to use the HDRI environment map as a background. The second option is Gradient allowing us to set a solid color, gradient, or fully transparent backplate for our render. The third option is Image that brings up a file browser and allows to open any image to be used as a backplate.

Two widely used options for jewelry renders are white and transparent backgrounds. The second option is particularly useful when you need to put the render on a website or presentation on top of another background/image. To get a transparent background, just set the fourth color channel (Alpha) to 0. Below, you may find two renders made with white and transparent backgrounds:

… or set floor material

Alternatively, you can assign textured material to the floor. For jewelry rendering, textures of natural stone or fabric are a good choice. We have downloaded marble textures from the ambientCG site providing PBR textures under the Creative Commons CC0 1.0 License. To get the marble material, we need to change the type of floor material to Principal and assign textures to texture slots:

To assign the texture, click on the corresponding slot and choose the texture file. For marble material, we need to set Base color, Roughness, and Base normal maps. Note that Light Tracer supports separate normal maps for the base layer and dielectric coat. This allows for more accurate modeling of complex materials such as carbon fiber which have a different geometric surface than the varnish layer. For the marble, we do not need coating, and thus we use only the Base normal slot. The glossiness of our floor material can be controlled with the Metalness parameter.

Please keep in mind that in addition to static images, Light Tracer Render also allows you to render videos with different camera trajectories for a better presentation of jewelry products. Video generation options are available on the View tab.

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