Next, we will create a single blade of grass.
- Create another default grid and rename it 'grass'.
- Enter the grid geo level.
- Create a Line and set it to be visible by clicking the blue right square of the node.
- Change the Primitive Type to Bezier.
- Change the Length to 0.5.
- Change the Points to 7.
- Go back to scene level and add Arnold Properties to the grass node by tab-typing Add Arnold Properties or choosing it from the Arnold Toolbar.
- This will allow the curves to be rendered in Arnold.
- Zoom into the curve and render the grass.
We now need to assign a shader to the grass.
- Go to mat and create another Arnold Shader Network.
- Create a standard_surface shader assign it to the curve.
- Change the base_color of the grass material to green.
- Increase the sss_weight to 1.
- Change the sss_color of the grass material to green.
- Change the sss_radius of the grass material to a darker green.
- Enable thin_walled (Geometry). It can provide the effect of a translucent object being lit from behind, ideal for thin (single-sided) objects, like bubbles and grass.
Now we need to override the radius of the curve to taper the grass. To control the radius of the curve and shape the grass we need to create an Attribute.
- Go to the grass object level and attach an Attribute Create node to the line.
- Change the name of the attribute to
- We are going to be using the inbuilt variable $PT which is the Point Number along the curve. However, it needs to be modified by an expression to taper the top into a rough grass shape. See below for the process in arriving at the expression.
- The final expression is:
Now we need to make the patch of grass.
- Create another grid (Toolbar > Grid).
- Create a Scatter node.
- Increase the Force Total Count of the Scatter node to around 10,000. This will give us many more points to copy the grass across.
- Connect the grid to the Scatter node.
- Create a Copy to Points node and connect the attribcreate and Scatter nodes to it.