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Color Mapping and Rendering#

Color mapping converts scientific values into colors. Select the values on the operator, then adjust the material or Colormap that renders the result.

Select a Color Field#

Use Colors [Field Selection] on an operator:

  1. Select Add Field under Field Name(s).

  2. Choose a scalar field, a vector-valued field, or several scalar components.

  3. Set Mode:

    • unchanged keeps the selected values.

    • vector_magnitude calculates one scalar magnitude from vector components.

    • selected_component uses Component Index from a vector.

Use unchanged for a scalar field such as pressure or temperature. For a vector stored as one (N, 3) array or as three separate scalar components, use vector_magnitude to color by magnitude. Use selected_component to color by one component of a vector-valued field. Adding a valid color field enables scalar coloring automatically.

Streamlines field selections with velocity components and Pressure color

Materials and Colormaps#

Surface operators such as Faces, Points, Glyphs, Iso Surfaces, Streamlines, and Planar Slices create an NVIDIA Material Definition Language (MDL) material below the operator. Select its Shader prim to edit:

  • domain: The numeric interval mapped to the lookup table

  • lut: The lookup-table texture

Kit-CAE includes afmhot, cividis, gist_gray, and gist_rainbow lookup-table textures.

Scalar-color Shader inputs for domain, lookup table, and color enablement

Volume and Volume Slice operators use a Colormap prim. Its color and opacity control points define the transfer function. Domain Boundary Mode controls values outside the domain:

  • clampToEdge uses the nearest endpoint color.

  • clampToTransparent makes out-of-range values transparent.

You can also create a reusable Colormap with Create > CAE Sources > Colormap.

Colormap source with domain, boundary mode, color ramp, and opacity control points

Control Automatic Rescaling#

Operators initialize material ranges from the selected field. Use Rescale Mode for the colors selection to control later updates:

  • clamp sets the range to the current field range.

  • grow expands the range when later values fall outside it.

  • disable preserves a manually authored range.

Set disable before authoring a fixed domain or Colormap range.

Colormap domain and control-point properties used for a fixed range

You can also lock an individual property. Set the value, right-click its field, then select Locks > Lock. Unlock it when the operator should update the value again.

Map Opacity from a Field#

Kit-CAE supports an independent opacity field on Faces, Points, Glyphs, Iso Surfaces, Streamlines, and Planar Slices.

  1. Under Opacity [Field Selection], add one scalar field with Add Field.

  2. Select the operator’s Shader prim.

  3. Adjust Opacity Domain, Opacity LUT, and the Opacity multiplier.

  4. Set the opacity Rescale Mode to disable when using a fixed domain.

Color and opacity can use different fields and lookup tables. A Colormap source publishes both its color ramp and the opacity values from its alpha control points.

Independent Pressure field selected for operator opacity

Try It: Tune the Color Mapping#

Continue from Try It: Visualize the Vehicle Dataset.

Volume#

  1. Select the Volume operator. Confirm that Colors contains the three velocity components and Mode is vector_magnitude.

  2. Set the colors Rescale Mode to disable.

  3. Expand the Volume to Material > Colormap. Set Domain to 0 through 30.

    Volume Colormap with a domain of 0 through 30 and clampToTransparent selected

  4. Set Domain Boundary Mode to clampToTransparent and adjust the opacity control points to reveal the wake.

Velocity volume with a tuned domain and transfer function

Planar Slices#

Continue with the independent Planar Slices created directly from Fluid_Domain in the previous section.

  1. Hide the Volume and show the Planar Slices operator.

  2. On the Planar Slices operator, confirm that Colors contains Pressure and set the colors Rescale Mode to disable.

  3. Select Materials > UnlitScalarColor > Shader and set domain to -400 through 400. Leave gist_rainbow selected or choose another lut.

    Planar Slices Shader with a pressure domain of minus 400 through 400
Pressure field around the vehicle after setting the color-map domain

Streamlines#

  1. Show the Streamlines and Faces operators. Hide other visualizations.

  2. On Streamlines, add Pressure under Colors [Field Selection] and leave Mode set to unchanged.

    Pressure selected as the Streamlines color field

  3. Set the colors Rescale Mode to disable. Select Materials > ScalarColor > Shader, set domain to -400 through 400, and choose a lut.

    Color ramp and domain controls for Streamlines

Move the Unit Sphere. Streamlines recompute from the new seed positions while the fixed color domain remains unchanged.

Pressure-colored Streamlines around the vehicle

Try Field-Driven Opacity#

  1. Hide Streamlines and show the Planar Slices operator again.

  2. Under Opacity [Field Selection], add Velocity_0, Velocity_1, and Velocity_2. Set Mode to vector_magnitude and the opacity Rescale Mode to disable.

  3. On Materials > UnlitScalarColor > Shader, set Opacity Domain to 0 through 30. Use Opacity LUT to control how values within that range fade, and use Opacity as an overall multiplier.

    Planar Slices using pressure for color and velocity magnitude for opacity

Color continues to use Pressure and its -400 through 400 domain. Opacity now uses velocity magnitude and its independent 0 through 30 domain.