Getting Started
with VNS 3: Fields
& Forest
Part 5F. Building Ecosystems (Understory) & Distance Dissolve
1. We have an Overstory of pine
snags and stumps and an underlying texture. All we need is a
young lodgepole pine Understory and the Pine Burn Ecosystem
is finished. Go back to the Pine Burn Ecosystem Editor Foliage
page.
2. Select the Understory Ecotype
and Add Ecotype  . Turn
to the Settings tab and change the Absolute Size
to Foliage Group and Absolute Density to Foliage
Group. Leave the Area Units at hectare.
3. Add Foliage Group and
name it Lodgepole Pine.
4. Set the Group Max Height
to 8 meters, Group Min Height to 5 meters,
and the Group Density to 200 stems per hectare.
5. Add Foliage Object.
6. Choose New Image Object
from the Image Object dropdown list.
7. Go to the Components\Image\Foliage\Conifer
folder. Multiple-select the Lodgepole11, Lodgepole12,
and Lodgepole13 images. The image extensions may be iff
or iff24. The iff24 extension is an older nomenclature
used to identify 24-bit color images and set them apart from
8-bit grayscale images with the iff8 extension. Either
way, VNS will load the images because it pulls image information
from the file itself and doesn't rely on the extension.
8. VNS will create Image Objects
for the additional foliage images loaded.
9. Save the project and render
a preview.
10. Save the Pine Burn
Ecosystem as a Component with Save the Component  .
11. Load the VNSLastRender.png
thumbnail from the WCSFrames folder.
12. Add your description in the
Comments section and Save to Disk & Close.
Madison Canyon, Yellowstone NP
Regrowth forest 10 yrs after major fire. Overstory of 20-30m
pine snags and 1-2m stumps. Understory of 5-8m young lodgepole
pines.
13. Move to the Grassland
Ecosystem. We had disabled its Understory to speed up rendering
during Ecosystem setup. Enable the Understory Ecotype.
14. Save the project and render
a preview.
15. The foreground Grassland
foliage rendered slowly until it got to a certain point, then
accelerated. The Understory has Distance Dissolve enabled,
which causes Foliage Objects to be replaced by texture when the
foliage renders at less than a Dissolve Height of 4
pixels. This is a render-saving option to keep VNS from rendering
every stem of foliage as far as the camera can see, which can
take a long time for a field of grass. When rendered Foliage
Objects drop below a height of 4 pixels, Dissolve Color is rendered
in place of the images.
16. Select Dissolve Color Texture
Operations and Edit Texture.
17. The texture is Fractal
Noise with 2 shades of grassy green. The Grassland Ecosystem
was designed for close views, so a complex Dissolve Texture wasn't
created. We just happen to have a Dissolve Texture that is more
appropriate for the scene, so Load Component  .
18. Load the Grassland Dissolve
Color from the Component Gallery.
19. Close the Texture Editor and reduce the Dissolve Height
to 2 pixels. Keep in mind that a dissolve height in pixels
will cause the dissolve to occur at different places in the view
depending on the size of the rendered image. If you want the
dissolve distance to be consistent between images of different
sizes, use Relative to Image Height.
20. Save the project and render
a preview.
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