The automotive lighting industry has evolved considerably in the last years and the demand for complex optical structures requires advanced design capabilities. Speos 3D Texture is a unique feature that allows to design and simulation of micro textures in the form of patterns on a given body’s surface. Its advantage relies on an optical simulation model of the patterns (mesh) instead of using an actual CAD geometry. The computation time and file size are thus reduced.
This example explains how to design, validate, and manufacture light-extracting patterns on a rear lamp lens using Speos 3D Texture.
Software Prerequisites
To be able to use this example, the following products and solutions need to be installed on your computer:
- Ansys Speos 2023 R1 or later
Overview
Understand the simulation workflow and key results
Predicting the light performance and appearance of automotive lighting devices requires the use of advanced software tools like Speos 3D Texture . Both design and validation of such lighting devices can be conducted virtually in Speos to then manufacture a physical part. The simulation results fidelity gives enough confidence to ensure a lower number of development iterations, reducing cost and time of the project.
Step 1: 3D Texture Design
The first step is to employ the unique Speos modeling capability dedicated to advanced patterns: 3D Texture. A parametric definition is completed to generate a simulation file to be validated.
Step 2: 3D Texture Validation
The 3D Texture is visualized and simulated in Speos. Qualitative and quantitative targets can be evaluated for different types of measurements.
Step 3: 3D Texture Manufacturing
The generation of 3D Texture in Speos outputs a data file containing the relevant information to manufacture a physical part.
This example requires Ansys Speos for steps 1 and 2 only.
Run and Results
Instructions for running the model and discussion of key results
Step 1: 3D Texture Design
- Extract files from [[3DTexture_RearLamps.zip]]
- Open [[3DTexture_RearLighting.scdocx]] from the ‘3DTexture_Automotive_START’ folder
- Define 3D Textures from the left and right sides based on the given parameters
- Compute 3D Textures
The design parameters of the 3D Texture will depend on the employed manufacturing technology, the required aesthetical appearance, and the existing optical design expertise. With Speos, it is possible to experiment with different inputs to achieve a design that meets all conditions.
In this specific use case, a clear polymer lens is utilized as a light medium with the intension to extract light from the 3D Texture patterns removed from it (see figure below). This ‘lamp’ is then used as a taillight device in a vehicle.
To achieve a proper luminance and lit-surface homogeneity, Speos 3D Texture needs the definition of multiple parameters including axis system, support, operation, pattern, and mapping (see definition panel below).
Axis system
First, the axis system must be defined. 3D Texture relies on a planar reference before it is projected onto any flat or non-flat solid support and, therefore, an origin point and two orthogonal lines are required. For this scenario, the selected axis system is oriented 45 degrees from the horizontal plane (third option below).
Support
The support is the target geometry where the pattern will be applied. Because a Boolean operation is conducted, the support is required to be solid and have a Speos material applied to it. For this lighting application, an optically clear material is applied to the support because light will travel through it.
Operation
Different Boolean operations are available to execute between the solid support and pattern. Speos, however, always displays the meshed patterns in blue. The actual behavior of the pattern is dictated by the selected operation as explained below.
|
Operation |
Actual behavior of the pattern |
| Remove |
|
| Add on different material |
|
| Add on same material |
|
| Add in |
|
| Insert |
|
The ‘Remove’ option was used in this case to build prisms that extract the light on the visible side of the lamp. The spacing between patterns and their intersection with the support is also crucial. More information can be found here .
Pattern
The geometry to be patterned shall be saved independently (as .scdocx). It is possible to scale it globally or relative to its X, Y and Z axes. A scale factor of "1" means 100% of the original pattern size. If the size of the pattern is changed with these scaling options, the parameters should be provided to the tool manufacturer as only Speos knows when a change in the pattern scale is applied.
Furthermore, the orientation of the patterns can be specified. Two options are available: ‘Constant’ and ‘Normal to support’. Because light extraction is expected to travel in one direction (rear direction of the vehicle), a ‘Constant’ orientation was selected.
Mapping
The mapping defines the details of the distribution of the patterns on the support. In Speos, there are rectangular, circular, hexagonal, and variable-pitch automatic mappings, but it is also possible to generate customized types.
The rectangular mapping used in this use case, for example, requires the designation of the distance between patterns along X and Y , the mapping length (size), and angular offset (tilt).
Lastly, the Limiting Surface must be selected for the 3D Texture to know where to reside. Since only one surface from the support body can be selected per 3D Texture, the left and right sides must be computed separately. The following image shows the left-side Limiting Surface selected on the support.
Step 2: 3D Texture Validation
- Add 3D Textures to provided simulations as geometries
- Compute simulations
Upon the completion of the 3D Texture design, virtual validation must be conducted in Speos. The lit appearance was defined as the most important metric of the design (i.e., light uniformity, color, luminance, etc.) but photometric performance can be evaluated, too.
The required optical properties for the geometries must be applied, and the specified light sources need to be created. Then, a Radiance Sensor is placed in front and side of the geometry that contains the 3D Texture to quantify the output luminance in cd/m ² .
An Inverse Simulation was concluded to be more efficient in terms of computation time and result quality for the appearance evaluation (luminance map). The obtained results are displayed below after the lit and unlit renderings are combined.
Thanks to the Speos Virtual Human Vision results, it is possible to quickly assess the light uniformity across the tail lamp considering the human eye factor. This wouldn’t be easy using a false color map containing a linear distribution of light.
Additionally, the photometric performance of the result can be evaluated against specific lighting standards such as SAE and ECE (most common in this industry). An Intensity Sensor is used for this purpose as shown in the Photometry test setup below.
The measurement results in candelas (cd) are shown below:
The rules from SAE J585 for taillights are list below:
Steps 1 and 2 for 3D Texture design and validation can be repeated as many times as necessary until the expected metrics are achieved.
Step 3: 3D Texture Manufacturing
- From the ‘SPEOS input files’ folder, open the generated OPT3DMapping files with Notepad
A Speos 3D Texture is materialized in two forms: a 3D mesh that can be visualized and simulated in Speos, and a mapping file defining the position, orientation and scale of each element in the 3D Texture over the support. The mapping file is a text file format with an *.OPT3DMapping extension.
The *.OPT3DMapping file is built according to the following structure:
First line: number of patterns to be built in the texture. 4,690 patterns in the example above.
Following lines: x y z ix iy iz jx jy jz kx ky kz
- x y z: coordinates of the pattern's origin according to the axis system selected (see ‘0, 0, 0’ below)
- ix iy iz: orientation of the pattern for X direction of the axis system.
- jx jy jz: orientation of the pattern for Y direction of the axis system.
- kx ky kz: pattern scale values for x y and z directions. A value of "1" means 100% of the original pattern size.
Ultimately, the information contained in the OPT3DMapping file should serve as the recipe for the creation of a physical part. The text information for the position, orientation and scale of the patterns may be reformatted to be compatible with other programs reading the 3D Texture data. The responsible party for manufacturing the physical version of the patterns should also receive the CAD model of the support body (lens) and the element to be patterned (in this example, the ‘A’ shape body), along with the axis system used for the position and orientation of the 3D Texture (point ‘0, 0, 0’ above).
In the image below, a physical small section of the 3D Texture geometry designed in Speos is shown.
Important Model Settings
Description of important objects and settings used in this model
Materials
It is recommended to employ the same optical properties to the 3D Texture support and patterns.
Sensors
For Radiance Sensors (appearance), make sure to position the sensor’s origin as close as possible to the lamp to ease the definition of the pixel size (resolution). For example, if the 3D Texture pattern size is 0.1mm, you must use a sensor resolution of 0.1mm or smaller to capture this detail in the result.
3D Texture visualization (bounding box)
Right-click on a 3D Texture on the Simulation panel and select ‘Options’. The XYZ coordinates and size allow for adjusting the visualization of the patterns in the 3D view. These values do not affect the content of the 3D Texture, but are for visualization purposes only. The images below show the bodies placed outside and inside of the visualization bounding box.
Meshing
The meshing values shown below were used in this example but are not universal. Start with default values and change these numbers as needed.
Additional Resources
Additional documentation, examples and training material
Related Articles
- Backlight Unit Analysis and Optimization . (Co-optimization of uniformity and brightness using 3D Texture feature)
Ansys Learning Hub courses
- Speos Getting Started
- Speos Workflow and Geometry Management
- Speos 3D Texture
- Speos Photometric Analysis Advanced