Often grass textures make your scene suffer as they look 'flat' and unrealistic as a bump map can't really represent the thousands of grass blades realistically. This is a really quick tutorial to demonstrate how you can use any rendering engine with the ability to displace geometry to create realistic-looking grass. Get suitable maps
As the default scanline renderer in Max doesn't support displacement rendering, the first thing to do is ensure you have set the renderer to mental ray, vray or whatever alternative one you use.
Ok make your shape as you normally would - I've picked an interesting torus knot just to show how flexible this technique can be. Apply a new material to it and pick a grass texture for the diffuse map. I've picked one from Medieval Textures, if you don't have an appropriate texture collection with displacement maps included, then click the two thumbnails below to load a couple of preview samples from Medieval Textures.
(note these maps have been reduced to 512 x 512 from the original 2048 x 2048)
The problem
Render this and you'll see it really highlights the issues with this technique - it'll look fine from a great distance, but up close like this, it doesn't really look like grass at all. However, you may want to spend some time ensuring that it is tiling correctly and not stretching the texture too much.
Displacing
Go back into the material editor and add a displacement map into the displacement slot and set the displacement amount to around 40.
This will tell the renderer how to displace the map itself.
If you now hit render, you'll see a much more impressive result, the renderer is now using your displacement map to modify and subdivide the geometry at render time to create some really good-looking grass.
Your object now has the detail you'd expect from grass, or indeed any similar real-life object.
The render
It looks much better and you could obviously use this technique for anything from garden lawns, to bushes and trees. Note that the render time will increase significantly, so you'll probably learn that you need to control what you displace and maybe have grass in the foreground using this shader whilst distant grass can use the more standard style texture.
Also if you want to make your grass more, or less detailed you'll find displacement controls under your renderer settings. Edge length and max subdivisions are the two key settings to look out for - increasing edge length and reducing subdivs will speed up your render at the expense of less detailed grass.
Anyway, hope this very quick technique demonstration will help you with your renders!
