[BUG FIX] Update texrepeat handling for mjcf

[bxtbold]

Description

Replaced converting numpy array elements (array.astype(int)) with np.ceil operation (np.ceil(array).astype(int)). The reason I used this operation is texrepeat values are positive.

Related Issue

Resolves #616

Motivation and Context

When mjcf texrepeat is handled, it is converted to integer. That causes some issues for values such as [0.5, 0.5] which is rounded down to [0, 0]. The zeros array ends up emptying the image_array at 307 and 341 of utils/mjcf.py.

How Has This Been / Can This Be Tested?

This is a minimal example to reproduce the bug.

import numpy as np

def reproduce_error():
    # emulating utils/mjcf.py from line 305 to 307
    image_array_before = np.ones((2048, 2048, 4))
    tex_repeat = np.array([0.5, 0.5]).astype(int)
    image_array_after = np.tile(
        image_array_before, (tex_repeat[0], tex_repeat[1], 1)
    )  # this becomes an empty array
    print(
        image_array_before.shape, image_array_after.shape
    )  # (2048, 2048, 4) (0, 0, 4)

    # emulate options/textures.py line 155
    np.max(image_array_after, axis=(0, 1))  # This will throw ValueError

def fix_error():
    # emulating utils/mjcf.py from line 305 to 307
    image_array_before = np.ones((2048, 2048, 4))
    tex_repeat = np.ceil([0.5, 0.5]).astype(int)
    image_array_after = np.tile(image_array_before, (tex_repeat[0], tex_repeat[1], 1))
    print(
        image_array_before.shape, image_array_after.shape
    )  # (2048, 2048, 4) (2048, 2048, 4)

    # emulate options/textures.py line 155
    np.max(image_array_after, axis=(0, 1))  # Works yeay

if __name__ == "__main__":
    reproduce_error()
    fix_error()

To test the changes in Genesis, download the zip folder from #616 and run the following:

import genesis as gs
import time

gs.init(backend=gs.cpu)
scene = gs.Scene(show_FPS=False, show_viewer=True)
scene.add_entity(gs.morphs.MJCF(file='floor_backing_room/model.xml'))

scene.build()

i = 0
while i < 100:
    scene.step()
    time.sleep(0.1)
    i += 1

Screenshots (if appropriate):

Checklist:

• I read the CONTRIBUTING document.
• I followed the Submitting Code Changes section of CONTRIBUTING document.
• I tagged the title correctly (including BUG FIX/FEATURE/MISC/BREAKING)
• I updated the documentation accordingly or no change is needed.
• I tested my changes and added instructions on how to test it for reviewers.

• I have added tests to cover my changes.
• All new and existing tests passed.

[YilingQiao]

Thank you!