Interactive Ray Tracing

You can use interactive ray tracing (Stellar Physically Correct engine) in local or distributed mode. Interactive ray tracing computes high quality and physically realistic images with advanced global illumination effects (such as accurate refractions and reflections, shadows, and caustics), and supports multiview display, materials, and ambiences.

Users that are not familiar with global illumination settings can use presets, and more advanced users can tune some settings in Live Rendering.

Before you begin:
  • Ray tracing has an impact on performance and some settings can be modified through the Visual Quality panel.
  • There are some limitations when using the Stellar Physically Correct engine.
See Also
Ray Tracing Cluster Monitoring
  1. From the View section of the action bar, click the appropriate ray tracing command.

    CommandDescription
    Stellar

    Starts interactive ray tracing in local mode using compute resources from the local machine.

    The command name reflects the hardware you choose in the Local Configuration section in the Preferences.

    Distributed Stellar

    Starts interactive ray tracing in distributed mode.

    A connection to the cluster specified in the Distributed Configuration section in the Preferences is established, and rendering starts.

    You also need to install and start the cluster to be able to connect from the 3DEXPERIENCE platform. For more information, see Ray Tracing Cluster Monitoring.

    Warning: This command is usable only if you have the DIR license.

    If an error occurs while connecting to the cluster, it is logged in the Stellar Rendering Log widget detailed in the next step.

    Important: By default, ray tracing is activated in static mode only (when you do not interact with the scene). In dynamic mode, the rasterizer (Stellar Realtime Native engine) is used instead to enable good performance when manipulating and editing the scene.

    In static mode, the scene is progressively computed which means that the ray tracing result is progressively converged and the visualization is periodically updated.

  2. Click Stellar Rendering Log (or press ALT+Shift+L) to display rendering information.

    By default, rendering information, progress information, and the rendering log are displayed. Clear or click the appropriate option at the top of the log panel anytime during the rendering phase to hide or show the associated information.

    InformationDescription
    Rendering InfoDisplays the renderer configuration, resolution, and target quality.
    Progress InfoDisplays a progress bar as well as the elapsed and estimated time for rendering the model.
    Rendering LogBy default, Verbose and Clean log on new session are activated but you can clear one or both options whenever required.
    • Verbose displays additional information in the log panel and in the log files.

      Log files are available in C:\Users\user\AppData\DassaultSystemes\CATTemp\Stellar\Cache.

    • Clean log on new session empties the log when you start a new session.

    The list below the two options lets you filter log messages based on severity: Progress (1), Info (2), Warning (3), or Error (4).

    Choosing level n displays log messages from levels n to 4.

  3. To close the log panel, click Stellar Rendering Log (or press ALT+Shift+L).
  4. To choose a ray tracing preset or to define advanced global illumination settings, do one of the following to open the Visual Quality panel:
    • From the View section of the action bar, click Visual Quality... .
    • Right-click in the 3D area, and then select Display > Visual Quality....

    Ray Tracing (active) is displayed in blue to indicate that it is the current render mode.

    Render ModeDescription
    GeneralRasterizer render mode that lets you define the static and dynamic visual quality.

    For more information, see Rasterizer Visual Quality.

    Virtual RealityLets you specify the visual quality in Virtual Reality (VR) experiences.

    For more information, see Rasterizer Visual Quality.

    Ray TracingInteractive ray tracing render mode that lets you apply predefined global illumination effects.

  5. In the Ray Tracing (active) area, choose a preset from the Static list.

    These presets are groups of settings that are provided by the app, or customized by the user. They are intended for users who are not familiar with global illumination settings, by allowing them to quickly select the most adapted configuration.

    Preset Description
    Outdoor Optimizes settings for outdoor scenes.
    Interior Optimizes settings for interiors.
    Caustics Optimizes settings for caustics.
    Custom Applies customized settings.
    User preset Applies customized settings saved in user presets.

  6. For more advanced users, click Advanced Settings .

    The Visual Quality panel is refreshed to display the settings you can customize.

    Warning: Customization is available only if Live Rendering is included in your role. In that case, advanced settings are also available from:
    • The Live Rendering section of the action bar. To do so, click Options , and then modify the appropriate settings in the Stellar area. See Live Rendering: Rendering: Rendering Concepts: About Rendering.
    • Performance preferences.

    Keep in mind that:

    • The settings available in the Visual Quality panel, in the Stellar options, or in the Preferences are identical. The manual override defined in the Preferences applies to all tabs and widgets. The quality settings defined in the Visual Quality panel or in the Stellar options apply to the current widget, and to the widgets you might open afterward.
    • Prefer the use of the Visual Quality panel or the Stellar options, unless you want to override a specific setting for all widgets. If a manual override is activated in the Preferences, the defined values supersede those defined elsewhere.

  7. In the Ray Tracing tab, do one of the following:
    • Choose a quality from the Static list to apply the same quality to all the settings in all the panel.
    • Choose a quality in the list next to each settings group to apply the same quality to all the settings in the group. The quality automatically switches to Custom.
    • Click to expand a settings group and define a value for each setting in this group. When you modify a value, the quality automatically switches to Custom.
  8. To specify your own values for each setting, use the sliders, the lists, or the boxes as required.

    The following settings are available:

    Accumulative Settings
    Option Description
    Target quality (dB) Defines the quality of the converged image as peak signal to noise ratio (PSNR).

    Low values (between 10 and 20) result in noisy images and a quickly finishing convergence and are suitable for preview rendering.

    High values (between 40 and 70) result in images without apparent noise but with a convergence time that might be very long. Such values are suitable for final frame rendering.
    Samples per frame Defines how many samples per pixel are traced before displaying the first ray tracing image.

    1 enables maximum interactivity. Set to values above 1 makes the first image less noisy at the cost of lower interactivity.

    Recommendation: Use values above 1 only for compute setups with high compute power like multi-GPU and cluster setups.

    The value of this option varies exponentially (1, 2, 4, 8, and so on).

    Max sample luminance Lets you activate or deactivate the maximum sample luminance option.

    If you activate this option, some parts of the computed images may be darker than they should be in reality. In return, image noise converges more quickly.
    Base value Defines the clamping value of result pixels.

    Lower values result in faster convergence but darken bright effects like highlights or emissive objects.

    This value is used as maximum sample luminance value for sample paths consisting of many ray bounces. For paths including just few ray bounces, or only specular bounces, higher max sample luminance values are used.
    Filtering Lets you activate or deactivate the Gauss anti-aliasing filter.
    Strength Defines the Gauss filter curve used for smoothing. The higher the value, the smoother the result.

    This option is available only when Filtering is activated.
    Denoiser Converts a noisy image into a smooth image and improves convergence time for a rendering.

    Click Denoiser, and then use Start iteration option to specify after how many frames the denoiser is enabled.

    Recommendation: Enable denoising only if the amount of video memory (VRAM) is above 8 GB.

    The Denoiser option can be activated if your GPU is:

    • a NVIDIA GPU with a compatible NVIDIA driver installed.
    • generation Maxwell or newer (for example, Maxwell, Volta, Turing, Ampere).

    Note: About the denoiser:
    • There is a kind of artistically painted style effect in the early stages, but this effect is removed when the image has converged more.
    • Enabling the denoiser automatically grays out the Denoiser option in the Visual Quality Manager.
    Start iteration Applies the denoiser after the specified number of iterations.
    Global Illumination
    OptionDescription
    Max path depth Defines the maximum number of ray bounces.
    Light TracingOptimizes simulation of caustics effects and indirect illumination.

    Recommendation:
    • Use this option for scenes with small light emitters or very glossy surfaces, and for interior scenes.
    • Clear this option in standard scenes for faster interactivity and convergence.

    Fast subsurface scatteringLets you switch between fast and accurate subsurface scattering simulation (SSS).

    • Fast SSS converges significantly faster but is only an approximation to reality.
      Recommendation: Use it for concept design and marketing.
    • Accurate SSS is physically-based but converges a lot slower.
      Recommendation: Use it for concept validation and light visualization.

    Ray offset (mm)Specifies the offset from a ray hit point at which new rays start.
    Downsampling factor
    Lets you enhance the rendering performance by applying a downsampling factor to the image displayed on screen.

    The image is generated with a lower resolution to have better performance but with a lower visual quality (the image looks slightly blurry).

  9. To save your customized settings in a dedicated user preset, click Save Preset .
    Important:
    • This command is available only if you choose Custom in the Static list.
    • You can save up to 10 user presets.

    The Save Preset dialog box indicates that the Static settings are associated with the new user preset and lets you enter a name for this preset.

    After clicking OK, the new preset is added at the end of the Static list and is automatically activated instead of Custom.

    User presets are stored across sessions, which means that you recover them next time you open the Visual Quality panel.

  10. To remove a user preset, make sure it is active, click , and then click OK to confirm.

    Note: You can only remove user presets created through the Visual Quality panel or the Stellar settings, not those created through Manage User Presets in the preferences.

  11. Click OK to store your customization in the Preferences, and recover it next time you apply the Custom preset.

    If you are not satisfied with your changes, click Cancel to restore the previous values.

  12. To exit ray tracing view mode, click Stellar or Distributed Stellar from the View section of the action bar.