This page provides a tutorial for creating grass in V-Ray for Modo.
To download the scene and assets used in this tutorial, please click on the button below.
Making the Hills
First, we need to create the hills on which the grass will appear.
1. Open an empty Modo project and create a plane. Scale its size up to 1000%.
2. Change the mode from Item to Component using the Shift + Space shortcut, then subdivide the plane five times (Shift + D).
3. Add a new empty mesh (N) and change the 3D viewport to Top view. Draw a couple of curves. Press Shift on every new one to reactivate the tool. Rename the mesh to Curves_for_hills. We will use it to shape the hills.
4. Go to the Setup layout and select the Plane geometry. With the plane selected, add a Curve Constraint Effector from the Deformers tab.
5. A pop-up window will appear. Select the Curve_for_hills mesh to assign the effector to the curves and click OK.
6. You should be able to notice the effect of one of the curves on the plane immediately. To enable the effector for all of the curves we drew, turn on the Use All Curves option from the Curve Constraint Effector's Properties. You can also increase its Threshold value to make the effect of the curves stronger, as well as use the transform tool to manipulate the position and shape of the curves until you have a hill-like looking plane.
Making the Grass
Now that we have a plane for our hills we are almost ready to create the grass. First, we need to make the scene flexible for randomization. We will divide the plane into three material tags - Foreground, Midground, and Background.
1. From the Top view, select one-third of the polygons and assign the material tag (M) Foreground to them. Repeat the step for Midground and Background, making sure that all polygons of the plane are assigned to one of the three tags.
2. We are now ready to add V-Ray Fur and assign it to our plane. Press the Add Item button in the Items list tab, navigate to the V-Ray Fur geometry and double-click it. Go to the Properties tab and assign the Plane to V-Ray Fur from the Geometry Items parameter drop-down menu. Duplicate V-Ray Fur twice so that there is one for each of the three sections of the plane.
3. Assign each individual V-Ray Fur to the Foreground, Midground, and Background materials we just created. This is done from the Material Tag drop-down menu of V-Ray Fur's Properties tab seen above.
4. Next, we are going to add the V-Ray Hair material to the three sections of the plane. Go to the Shading tab, select the Foreground material, click the Add Layer button and add V-Ray Hair. Repeat the step for the Midground and Background shaders.
Grass texture randomization
Now that we have V-Ray Hair assigned to all three sections of the plane, we can proceed with the grass texture randomization.
1. Open the Preset menu (F6) and navigate to the Grass images (Assets > Images > Organic > Grass). Drag and drop Grass01 above V-Ray Hair within the Foreground material. Change the Effect of the image to vhair Overall Color and duplicate it twice. Distribute the two duplicated images above V-Ray Hair for the Midground and Background materials in the same way.
Next, we will set up Grass01 as a texture map for a V-Ray Color Correct texture.
2. Go to the Shading tab and select the Foreground material. Click Add Layer, add a V-Ray Color Correct texture, and change its Effect to vhair Overall Color. Then enable the HSL On parameter and set a higher value for HSL Hue Offset. Group the two textures together (Ctrl + G). Repeat for the Midground and Background materials.
3. Open the Schematic layout then drag and drop the three pairs of textures in it. Link the Grass01 Texture Color channel to the Texture Map slots of the three V-Ray Color Correct textures.
We have successfully created our first texture group. However, in order to achieve more realistic grass color variation, we need to repeat the process with another grass texture.
4. Pick Grass03 and repeat steps 1 - 3, this time making sure a negative HSL Hue Offset value is set to each new instance of V-Ray Color Correct.
5. Add a V-Ray Noise texture at the top of each newly created texture group and change its Effect to Group Mask.
Grass geometry randomization with V-Ray Fur
Next, we are going to set up V-Ray Fur for grass geometry randomization. By default, V-Ray Fur uses 1000 units per area. This is a good starting point but its not enough for good looking grass. First, we will make sure that the grass is dense enough by assigning selection sets to the three sections of the plane and duplicating V-Ray Fur.
- Change the 3D view to Render Camera and select all visible polygons from the Foreground material, right-click and choose Add to Selection Set. Enter Foreground as a name for the selection set in the pop-up window that appears and click OK.
2. Go to the Items tab and select one of the three instances of V-Ray Fur we created in the beginning of the tutorial. Go to its Properties and change its Selection Tag to Foreground.
3. Duplicate that particular instance of V-Ray Fur twice, and rename the new ones to V-Ray Fur_4_short_strands and V-Ray Fur_4_long_strands respectively. Group them together as V-Ray Fur_Foreground.
4. Select V-Ray Fur_4_short_strands and go to its Properties. Change Hairs per unit area to 5000 and reduce the Length. Do the same for V-Ray Fur_4_long_strands, but this time set a lower value for Hairs per unit area and higher for Length.
5. Repeat steps 1-4 for Midground and Background. Feel free to input different values for the Length and Hairs per unit area parameters of the three different sections of the plane as this will produce greater randomization. You can also increase the Knots value to make fur strands uniform if the Length value is too high.
6. Render and observe the final result.
The scene was further enhanced with replicators and asset geometries from Modo's default library (rocks and boulders), V-Ray Sun and Sky, an HDRI environment map, a V-Ray Camera enabled, and minor post-production corrections. All assets used for the final render are available for download within the assets folder.