A suitable post effect configuration can extract object outlines and control the line width to achieve a drawing style, which is familiar from technical illustrations.
Tutorial level: Advanced
Example project: 'samples/rendering/outline_drawing'
1. Load in 'outline_drawing.r3d'. To apply it to your existing geometric objects, enable 'Selected Sections Only' in the File Load window and uncheck 'Objects' section. Use 'Replace' loading if you want to clean up some unnecessary items. Otherwise clear the Replace option to add the items to your current libraries.
2. If the scene is not included in a closed environment, add a camera backdrop to the current camera. Otherwise empty space areas will render fully black.
|A backdrop plane works well in orthographic rendering. If you plan to render a perspective image, create a camera-centered analytic sphere around the scene. In orthographic rendering, backdrop plane has a constant distance from the camera. In perspective rendering, a sphere defines the constant distance background.|
3. For maximal rendering speed, you can delete all materials except perhaps some outline area definitions, which you might use, from to the material library. The example configuration outputs only black and white lines so material evaluation will not be needed. Do not delete materials if you want to customize the style and include your own effects, which use the shaded color information.
4. Go to render settings tab and drag and drop 'Outline_render' to a view window. If maximal rendering speed is important, you can raise the Undersampling x and Y values from 1*1 to a higher level. Especially when rendering a high resolution image to a disk file, undersampling can be raised up to the maximal level.
The characteristic features of the Outline_render settings are:
Distance and bump normal channels trigger more accurate sampling
Lighting and volumetric computations are turned off and antialiasing is zero
Antialiasing method is geometric to keep sampling intervals regular
5. Go to the Post Effects tab of the select window and drag&drop TechStyleLines to the view window. Check in the view property window that you do not have other 'per image' post effects applied.
6. Render a test image. If you get too many lines, select the Edge Detection post effect and increase the Threshold and Normal Threshold values. Lowering the thresholds adds more lines to the image. If some object borders are drawn with a thin line although they should be thick, select the object_boundary_lines effect and lower its threshold value.
7. 'draw_lines' effect defines the line width range from thin to thick lines. Change it if necessary.
8. If you do not want to see all surface and object borders, select the post effect include_object_outlines and set the 'Exclude object outlines' checkbox. Note that you can customize the object outline density using materials which assign Surface:Identifier channel values. This example project includes 12 such materials. For example, the hierarchy below forces object outlines between part1 and the rest of the scene. There will be no other object boundaries.
9. 'Linewidth control' effect defines line thickness categories. Currently 5 line types are available:
1. Boundary line width = Width of lines between 2 disconnected surfaces
These lines types are not exclusive. If a line meets two or more type conditions, maximum width is used.
10. For the best possible quality, select the TechStyleLines effect, open the property window, go to Scaling tab and set Output Scale X and Y to 0.1. A lower value such as 0.25 is suitable for test renders.
|Edge detection depends on the image resolution and post image's Output Scale value. High resolution means that trigger channels usually change less between adjacent pixels. It may be necessary to readjust the edge detection thresholds after selecting the final output resolution.|
|The post effect combination uses many channels, some in floating point form. The deep image requires very much ram. Use of a high number of render boxes (Render settings/Distr tab) is therefore recommended.|