Creating Grass using ScatterTutorial By Aaron Dabelow, Using 3DS Max 8
Creating Textures: The first, and most important step to creating visually appealing 3-D grass, is creating the proper textures. We will need to create 3 texture maps for this tutorial; the diffuse channel for the grass, the alpha channel for the grass, and the diffuse channel for the ground.
The Ground: The Diffuse channel for the ground is what will appear underneath the grass, there are two ways to do this. The first is use an actual image of the ground, which is what I did. I took this picture in some nearby woods, after climbing a tree, and you can download this low-res version. You can easily create your own, or find one online.
Alternate: If you are going to have very thick grass, or don’t wish to use an image, you may simply apply a noise map to your ground plane. I chose a de-saturated brown, and a de-saturated green, set the noise type to fractal and set the size to 10.
The Grass: For this step, I took an Image of a tuft of grass, and removed the background in Photoshop; you could use any photo manipulation software to do this, so all that is left is the silhouette of the grass. Duplicate the layer and gausian blur it, make sure that the blurred layer is beneath the original one. Duplicate the blurred layer, and combine both blurred layers. What this has done is bleed the color out around the image of the grass, and still kept the original image. You have now completed the diffuse map for the grass.
The Grass Alpha: Now, take the file we were just working with and duplicate the original image layer, without the blurring. Bring its saturation to zero, and play with the contrast to make it mostly white. Duplicate, and gausian blur but only slightly! make sure it is less than the diffuse bleeding. All you want this blur to do is take the sharpness off of the edge of the leaf. This is done so the grass won’t appear aliased (jagged edged) in the final renders. This is what the earlier bleeding was for, to allow the alpha mask to be smooth, but not catch any of the diffuse channel that wasn’t the right color.
Final Texture file: Now combine all of the alpha mask layers together onto a black background, and place that at the top of your layer stack in Photoshop. So it looks like the image I have here. Make sure you have only the diffuse chanels turned on, and the alpha mask turned off. This will be important later when we are composing our material in 3D Studio Max.
Creating Materials: Open up the material editor in Max, and create a standard Blinn, Under the “Shader Basic Paramaters” Check the “2-sided” box, and the “face map” box. This will make the texture show from both sides, and display properly in our field. Then under the Maps rollout, in the diffuse channel load up our Photoshop file. Click Open, and under the .psd input options, click okay. Next move on to your Opacity map, start off doing the same thing, load up our Photoshop file, but this time when prompted with the .psd input options, click on “individual layer” and even though we have the mask layer turned off, it appears, and we can select it. Do so. I really like this method of selecting individual layers, so I can keep all of my maps in one file for one material. Very useful for keeping Bump, Opacity, Specular, and Diffuse maps all in one file, and this shows the importance of labeling your layers, and keeping things neat.
Setting up our scene: Now we are ready to create our scene in max. Create a plane with several subdivisions, and bend it around to look like you want it, Soft selection and noise are very useful for these tasks. Then apply the ground material that we discussed in the first step.
Then create a plane, with no subdivisions, just one polygon, and make it proportionate to your ground and scene for one tuft of grass. This will end up being the geometry for all of the grass. Duplicate and rotate the single face twice, so you have a total of three planes, in a star pattern. Then make one of the planes taller, and the other shorter. This will give some variation to the grass clumps. Now under the Edit Geometry menu in the Modify Panel, attach all three of the planes together, so now it is one piece of geometry, and add our grass material to it.
Finishing up: Select the newly made tuft of grass and go to the create panel, and under compound objects, click on “scatter”. Under “pick distribution object” select the ground plane. Go down to “distribution object parameters” and uncheck “perpendicular” this will stand your grass upright. Go down to “display” and change the percent of scatter objects from 100% to something more manageable, like 10%, and check the box that reads “hide distribution object” Now this is where it gets tricky. You will need to play with all of these settings to get your desired result, but here is what worked for me.
Final Image: Trow in some lights and set it to render, Let me caution you against Final Gather, or Skylight, despite the fact that it makes it look awesome, it can seriously slow you down. If you really want to use it, turn your shadow samples down to around 5 to 7. And with any luck and some time you’ll end up with something looking about like this, or better.
If this helped, i’d like to hear back from you, of if you have any amendments to make.
Here is the newest version of the Dabelow tool box. It is the updated version of the tool box below. I closed off the unfinished scripts with dialog boxes, and added two new features.
