Ghosted Illustration from 3D CAD

Using NX Non-Photo-Realistic render

method to generate source images for

technical illustration.

Step by Step

2015-12-14 Matthias Ahrens

Ghosted Illustration from 3D CAD

2 2015-12-14 / Ghosted Illustration from 3D CAD / M. Ahrens

• Present inner parts in context of the outer product design

• Using SIEMENS PLM NX 3D CAD model as source for a technical illustration

• Using NX embedded Lightwork Design Ltd. render engine

• Reduce utilization of external tools to a minimum to react faster on design

changes

The intention


• Identify components of interest

• Define a accurate camera for reuse

• Define (Section) views for the different levels of depth

• Set background

• Set lights

• Set floor

• Define Visualization Scene for synchronizing multiple Model Views

• Set resolution, size and quality for rendering process

• Render multiple passes of artistic images

• Compose final image in graphic tools (e.g. GIMP)

The process


• Analyze the CAD model and identify the components resp. areas of interest,

which should be presented in context and focused via the illustration.

• The “View Section” command can be used to identify inner areas.

Identify components of interest


• Define a Camera and take care for “Perspective” and “Lens” settings.

• Recommendation: Use a “Zoom to” value of 50mm

Define a accurate camera for reuse


• Based on the areas of interest define multiple “Model Views”.

• Create “Cutouts” to provide direct views from camera position to details.

• Recommendation: Use the following steps to define such views.

Define (Section) views for the different levels of depth

L00 L01 L02


• Create a set of closed curves for the cutout section on a new datum plane.

• Remember camera’s point of view to get best section lines (red & magenta)


L00 L01 L02


• Use the “PMI” function “Section View…” to generate related cutouts.

• Attention: “Lightweight Section View…” cannot be used for rendering!



• If components are not tackled by the “Section View…” command, the

Assembly – Context Control command “Hide Components in View…” can be

used to hide components in the current work view only.



• Switch to Advanced Studio mode and enter Scene Editor.

• Take care that the lights producing shadows to provide information of depth.

• HDRI resp. Image Based Lighting is not required here.

Enter visualization environment


• Often a white, plain background is preferred for technical illustrations.

Set background


• Switch to Advanced Lights setting and generate simple lighting schema.

• Take care for intensity and shadow generation!

• Verify lights definition in “Scene Editor” to ensure accurate setup!

Set lights


• Ensure that IBL (Image-Based Lighting) is not used!

• Even if IBL is producing sometimes more realistic

results for High Quality Images the shadow control

can become worst for Artistic Image renderings!

Set lights

Artistic Image:

High Quality Image:


• Similar to the standard Three-Point Lighting for

photographs the light setup for artistic images is

important to compose accurate shadow results.

• A dedicated RIM resp. Back Light is not required here!

Set lights

By an accurate intensity setting for the

Key Light and the Fill Light a shadow

result at two levels can be achieved!


• Activate the floor as Shadow Catcher to nail the product to the ground.

Set floor


• The most of the scene settings will be defined and stored in context of the

model view!

• Therefore it is recommended to generate a dedicated “Visualization Scene”

for this product shot in a new “Palette”!

Define Visualization Scene for synchronizing multiple Model Views


• Apply the new, custom “Visualization Scene” to all custom model views,

which will be used for the ghosted illustration.

• You have to update and reapply these “Visualization Scene” whenever an

adjustment of the lighting is required.

Define Visualization Scene for synchronizing multiple Model Views


• Use the High Quality Image dialog to adjust preferences for the Lightwork

Design Ltd. software render engine.

• Settings like “resolution” will be honored by the Artistic Image algorithms too.

Set resolution, size and quality for rendering process

Example of required image sizes and resolutions:

Width: 297mm 7016px 3508px

Height: 210mm 4961px 2480px

Resolution: 600dpi 300dpi

• Be carefully with the size of the

image!

• Larger bit planes can increase

render processing time dramatically!


• Run a few tests at lower resolution with the “Artistic Image” - “Cartoon” or

“Color Wash” and “Lines and Shadows” to check shadows and colors.

• If required, adjust colors of bodies to realize better contrast.

Set resolution, size and quality for rendering process


• Render “Color Wash” and two times “Lines and Shadows” at final resolution.

• Take care that is activated for “Shadow” cycles only.

• Flip black/white for “Lines and Shadows” to separate them into two passes.

• After each pass use the “High Quality Image” save dialog without closing the

“Artistic Image” dialog to store the images.

• In the “Save Image” dialog enter the file name extension “.jpg” to force JPEG.

Render multiple passes of artistic images


• Based on detailing level process “Artistic Image” for each slice of illustration.

• Hide unwanted bodies and components per slice.

• Take care for camera position (reapply camera upfront each rendering cycle!)

• Take care that at least the zero layer shadow image contains ground

shadows by activating the stage floor.

Render multiple passes of artistic images

L00 L01 L02


• Load all images as “layers” into image manipulation tool (e.g. drag and drop).

• Sort them in a logical order with the nearest layer on top.

Compose final image in graphic tools (e.g. GIMP)


• Make the “white” the transparent area in the “Lines” and “Shadow” layers.



• Ad a “Layer Mask” to the “Color Wash” layers and paint the areas, which

should become transparent with the “Airbrush” tool.



• Use the various Hide/Show options and the Black/White colors to adjust level

of transparency and review result across multiple layers.



• Use the “Opacity” slider to adjust “Shadow” intensity.



• Add “Layer Mask” to “Lines” layers too and vary area of transparency to let

the lines become a little bit longer or shorter than the shaded areas.



• Use “Gaussian Blur” effect with larger values on “Layer Masks” to smoothen

transition between opacity and transparency areas.



• Use “Gaussian Blur” effect with smaller values on outer “Color Wash” and

“Shadow” layers to achieve a kind of “Out of focus” effect.



• Export the image into a common format (e.g. jpg) and keep the image in

GIMP file (.xcf) format for later adjustments or fine tunings.

• Keep in mind… the camera position and color settings are still stored in the

NX CAD file.

• In cases of iterations a redo of the rendering and the composing is required.

• But maybe only a few “slices” have to be revised while the outer shell is still

valid?



The result


• The 3D model “Axial Pump”,

used for this illustration, was

gathered from GRABCAD and

was designed by

Kostiantyn Abramov

The 3D model source

Ghosted Illustration from 3D CAD

Engineering