Setting Image Frame and Quality Parameters


This task shows how to define the rendering style and quality parameters. 
Open the Shooting.CATProduct document and make sure that Shading with Material is selected in the View toolbar.
  1. Click Create Shooting to open the Shooting Definition dialog box the select Shooting 1 from the Shooting Name list:

    In the Frame tab, the Scene area lets you specify the elements to be rendered as well as the way of rendering them. By default, the active environment and any other active source are rendered.
  2. In the the appropriate boxes of the Scene area, select the Camera, Environment and Available Lights you want to render.

    If no light is selected, a default directional light orthogonal to the image plane is used (therefore producing very few shadows).
    As it might take a very long time to compute the preview when working with large models, no preview is displayed by default.
    However, you can now click the Camera View button to display a preview of the camera or of the current viewpoint (depending on what you selected in the Camera list).
    In our scenario, the result looks like this when clicking the Camera View button:
    Once the preview is displayed, the Camera View button is grayed out and remains deactivated unless you select another value in the Camera list.
  3. In the Image size area, define the size of the rendered image using the slider or manually. 

  4. Indicate the ratio between the frame height and width in the Custom box.

    By default, the pixel number is locked: . However, the pixel number and the ratio can be linked together so that, whenever you change the pixel number, the ratio value is adjusted according to this number and reciprocally. To do so, click the Lock Size Ratio button (which turns green ).
    You can also click Predefined to retrieve standard ratios. The corresponding ratio and pixel number is then displayed accordingly.
  5. In the Output area, select On disk to modify the name of the computed image. By default, it is saved in a temporary folder under the name "CatiaRender.tif".

    The On disk option also lets you change the default location. For more information, refer to the Saving Pictures task in this guide.
  6. The Quality tab lets you specify rendering, shadow and accuracy parameters, all of them impacting the rendering computation duration.

  7. Indicate the maximum number for:

    • Reflections
    • Refractions
    • Rebounds (the maximum number of times a ray, either reflected or refracted, can rebound onto a surface).

    For instance, if you choose 2 reflections and have two parallel mirrors in your scene, you will see the reflections of the reflections in each mirror ; choosing 1 instead, you will not see the secondary reflections.

    Note: the number of rebounds cannot exceed the sum (Reflections + Refractions) and cannot be lower than 1.

    No texture rendering means that only the material lighting characteristics is taken into account for the rendering and the environment wall texture are not rendered as well. This option can be used to speed up rendering at early stage for example.

    If you select the Show shadows check box, only the shadows produced by the active lights are rendered, otherwise no shadows are computed. This can be useful to speed up rendering.

    Now, let's define the accuracy parameters that control the oversampling of the final image:
  8. Select the accuracy type.

    Predefined: sets a fixed sag value for calculating tessellation on all objects.

    • a low value means that a very fine mesh is used to render surfaces, but the drawback is that pre-processing and rendering will take more time

    • a high value means that a very coarse mesh is used, but the advantage is that pre-processing and rendering will take less time.

    Custom: these parameters are defined through three values: a minimum number of samples, a maximum number of samples and a threshold.

    • minimum sample: specifies the minimum number of samples, i.e. minimum number of
      rays taken at each corner of a pixel square to measure the color. In our example, we 
      have chosen a minimum of 1 ray at each corner of a square of 4 × 4 pixels
    • threshold: specifies the percentage over which an oversampling is done if the contrast
      in any RGB component between the currently calculated pixels and the neighboring
      pixels weighted by their sum is greater than this threshold.
      The lower this value, the more oversampling and the longer the rendering time
    • maximum sample: specifies the maximum number of samples, i.e. rays, per pixel. 
      In our example, we have chosen a maximum of 1 ray per pixel.

    The preview area to the right shows you the effect of each setting.

    Anti-aliasing sets a better oversampling by modifying the appearance of lines in order to make the jagged edges look smoother. To do so, the square pixels composing the lines are put in shades of gray or in-between color.
  9. Click the Animation tab to define the animation parameters. For more information on the animation, refer to the Defining Animation Parameters task in this guide.

  10. Click OK.

    The next step is to render the shooting you have defined.
  11. Click Render Shooting to open the Render dialog box.

    A summary of the selected scene characteristics (viewpoint, number of active lights, shadows activated or not, etc.) is displayed.

  12. Select a shooting then click the Render Single Frame button or the Render Animation button, depending on the type of render you want to create.

    The Rendering Output window opens and displays the rendering result.
    You can also render an animation or a single frame by right-clicking the desired shooting in the specification tree then selecting Render Animation or Render Single Frame.
    The background colour of the Rendering Output window depends on the background color set in Tools > Options > General > Display > Visualization.
    After selecting an animation as the current shooting, the Compressor Setup... button is activated to let you set the type of compressor from the Choose Compressor dialog box:
    This dialog box allows you to choose a CODEC from the list of CODECs installed on your computer, then configure it. The role of the CODEC is to compress your video files.

    Installing Version 5 does NOT install CODECs on your computer. The list of CODECs differs from one platform to another. For information about how to configure the CODEC, refer to the CODEC supplier's documentation.

    On Windows, the Compressor list contains several options among which "Full Frames (Uncompressed)". Selecting this option prior to recording has the following effects:

    • the resulting video file is larger (because it is not compressed)
    • but performance during the recording is enhanced (because each frame is not compressed as soon as it is recorded).

    Note that if you installed DirectShow on your computer, you will be able to use all CODECs and compression options provided by the DirectShow multimedia architecture. Therefore, additional CODECs will be available in the Compressor list.

The following images illustrate different types of rendering:

Textures off, two active lights, shadows off and an
average accuracy

Textures on, two active lights, shadows on,
anti-aliasing off and the lowest accuracy

Textures on, two active lights, shadows on
and the lowest accuracy

Textures on, two active lights, shadows on 
and an average accuracy

In the specification tree, the icon identifies the most recently rendered shooting, the other shootings being identified by the icon.
Click Redo Render if you want to redo the last render performed, whether it was a single frame or an animation.
Once a shooting has been defined, you can edit its parameters afterwards by re-accessing the Shooting Definition dialog box. To do so, right-click the shooting to be modified in the specification tree then select Shooting object > Definition.