The new grass extension in Maxwell Render 2.7 allows you to quickly add grass to selected geometry and has many parameters to control the look of the grass. Its implemented in SI as an object property, which allows you to have as many separate grass "components" as you want, attached to one object.

To learn more about the Grass extension, please see the Grass page in the Maxwell Render documentation, and the Grass Examples in the Knowledgebase for some example settings and materials.

Applying grass to an object

Select the object(s) and go to Property>Maxwell Grass. A new custom property set will be added to the object, along with a hidden point cloud parented to the object (used for displaying the blades in the viewport using SI Strands). Changes in the grass parameters such as density, length, nr of points per blade, and any maps you add to a parameter, such as a density map, will be reflected in the viewport display of the strands.

Maxwell Grass previewed in FIRE

Applying materials to the grass

A material in SI must be specified by name, and it must be attached to an object or the material won't be exported to Maxwell. For these reasons, you need to apply the grass material to an object in the scene (which should probably be out of view). Then open the MaxwellGrassAttrs parameter set, click on "Pick Material" and select the object with the grass material applied to it.

Each MaxwellGrassAttrs parameter set can use its own material and settings.

Mapping the grass parameters

Most of the grass parameters can be mapped, such as Density, Length, Cutoff, Angle etc. More information can be found in the Grass page in the Maxwell Render documentation.

Softimage does not support connecting textures to nodes which aren't shaders. Therefore, the maps must be specified as file paths and there are no settings (invert, tiling, adjustments).

"Global scale factor" vs Grass parameters

The Global scale factor in Renderer Options (Globals tab), controls how Maxwell interprets 1 SI unit. The default setting of 1 means 1 SI unit = 1 meter in Maxwell. If you change the Global Scale factor, the grass viewport display will update to reflect how the Density and Length would look with the new Global scale factor.

In the example below, on the left, grass was applied to a default grid of 8x8 SI units. The Global scale factor is at the default 1, meaning to Maxwell this grid is 8m x 8m big. The default grass settings with 2000 blades/m were used and Display percentage in the Grass parameters was set to 100 so that all the blades are visible in the viewport.

In the right image, the Global scale factor was changed from 1 to 0.1, meaning to Maxwell the grid is now 80cm x 80cm. The grass display updates to reflect what the current settings would look like when rendered.

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