How to set terrain texture?

[tesslerc]

When spawning a terrain from height_field it is rendered as a smooth white surface. As opposed to the standard MuJoCo blue checkered plane.

How can we set the terrain texture? This is very important to enable proper visualization of the motions.

[jgillick]

Basically, you need to apply a surface in the add_entity call, and there are two ways to do it to acheive what youre asking:

Stretched Image

Stretches an image across the entire plane. This is likely not ideal if you want smaller tiling.

terrain = scene.add_entity(
    surface=gs.surfaces.Rough(
        diffuse_texture=gs.textures.ImageTexture(
            image_path="textures/checker.png",
        )
    ),
    morph=gs.morphs.Terrain(
        n_subterrains=(2, 2),
        subterrain_size=(6.0, 6.0),
        horizontal_scale=0.25,
        vertical_scale=0.005,
        subterrain_types=[
            [ "random_uniform_terrain", "discrete_obstacles_terrain" ],
            [ "wave_terrain", "pyramid_stairs_terrain" ],
        ],
    ),
)

Tiled image

You can use numpy to tile your image texture across the plane. In this example, I told numpy to create a 10x10 image grid from the original image. This new tiled image will be stretched across your plane. If you want the tiles to be a specific size, you can calculate the desired grid number by the overall plane size.

import numpy as np
from PIL import Image

...

# Create a numpy array of shape (4, 4, 3) and type int8 with alternating values of (255, 255, 255) and (0, 0, 255)
checker_image = Image.open(os.path.join(gs.utils.get_assets_dir(), "textures/checker.png"))
image_arr = np.array(checker_image)
tiled_image = np.tile(image_arr, (10, 10, 1))

terrain = scene.add_entity(
    surface=gs.surfaces.Rough(
        diffuse_texture=gs.textures.ImageTexture(
            image_array=tiled_image,
        )
    ),
    morph=gs.morphs.Terrain(
        n_subterrains=(2, 2),
        subterrain_size=(6.0, 6.0),
        horizontal_scale=0.25,
        vertical_scale=0.005,
        subterrain_types=[
            ["random_uniform_terrain", "discrete_obstacles_terrain"],
            ["wave_terrain", "pyramid_stairs_terrain"],
        ],
    ),
)