Refining a Vector Display

Simcenter STAR-CCM+ allows you to view vector fields using either arrows (glyphs) or a texture-based method known as line integral convolution. For each method, multiple properties are provided for customizing the appearance.

The scene must contain a vector displayer with parts assigned. By default, the Function chosen on the Vector Field node is Velocity.
To choose between arrow or texture-based visualization:
  1. Select the [vector displayer] node and set Display Mode to either Glyph (for arrows) or Line Integral Convolution (for texture). Line integral convolution requires more computing resources.
    When using line integral convolution there is some delay before the effect of a property change is seen in the graphics window.


    Figure 1. Vector scene rendered using glyphs


    Figure 2. Vector scene rendered using Line Integral Convolution
By default, the vector field is colored according to the vector magnitude of the vector field. Other options are available including constant color, preset material, or according to an additional scalar field. This latter option is useful for when you want to detect correlations between flow direction and another quantity in the simulation.
  1. To set the method by which the vector field is colored, select the [vector displayer] node and modify Color Mode.
Other properties available on the [vector displayer] node include Projection Mode, which allows you to display only one component of the vector relative to the chosen part. For a full list of properties and their use, see Displayer Properties Reference.
  1. When using arrows (glyphs), you can apply proportionate or constant sizing as follows:
    1. Select the [vector displayer] > Glyph node and set Vector Length to either Vector Magnitude or Constant.
      This choice affects how other sizing parameters are applied, as follows:
      • Vector Magnitude: sizing parameters are applied to the largest arrow and the rest are sized in proportion
      • Constant: sizing parameters apply to all arrows equally
    2. To control the relative sizing of arrows throughout the scene, first set the Vector Scale property to one of the scaling methods and then modify the value in the Glyph > [Absolute/Relative/Direct] Length node.
      For example, to ensure that vectors appear the same size regardless of zoom level, set Vector Scale to Screen Size, select Glyph > Relative Length and set Glyph Length (%) to a suitable value.
    3. If too many arrows appear in one location, (for example, within a mesh refinement zone), then you can reduce the density using one of the following methods:
      • Set Vector Spacing to Geometric, select the Glyph > Geometric Spacing node and activate Randomize. Then, increase the On Ratio to a value higher than 1 and observe the change in vector density. For example, an On Ratio of 2 only shows every second vector in the scene.
      • Set Vector Spacing to Uniform, select the Glyph > Uniform Spacing node and set N Grid Points to the number of locations (horizontal and vertical) at which a vector is displayed. This number of arrows remains constant regardless of the zoom level.
    4. For other property descriptions, see Vector Controls Reference.
  2. To adjust the appearance of the texture when using line integral convolution:
    1. To reduce the amount by which the underlying texture shows through the rendered surfaces, select the [vector displayer] > Line Integral Convolution node. Decrease the Color Transparency closer to 0. A value closer to 1 shows more of the texture pattern at the expense of color in the scene.
    2. Line Length increases the length of the integrated line. A low setting produces a "noisy" result (short lines). With a high setting the lines appear very long.
NoteAt high resolutions, hardcopy export with line integral convolution may fail due to graphics hardware memory being exceeded. If this error occurs, try lowering the resolution to 4096 pixels or less, or alternatively enforce Mesa OpenGL for software-based rendering. (Preferably configure Mesa SWR graphics with up to 16 renderer threads.)
Experimenting with the various controls and properties is a helpful way to learn how they affect the final image. Further advice is available in the articles posted on Support Center.