Bug for rendering normal map?

[Uio96]

Describe the issue

I find that when rendering normals map, the bproc.renderer.enable_normals_output() operation has to be put after bproc.camera.add_camera_pose() to make it function properly. Otherwise, the output will be blank.

I am not sure if that is a special design or a potential bug. I do not go into the details of enable_normals_output operation. But if it is a special design, maybe it is better to state it in the tutorial or some examples.

Minimal code example

import blenderproc as bproc
import argparse

parser = argparse.ArgumentParser()
parser.add_argument('camera', help="Path to the camera file, should be examples/resources/camera_positions")
parser.add_argument('scene', help="Path to the scene.obj file, should be examples/resources/scene.obj")
parser.add_argument('output_dir', help="Path to where the final files, will be saved, could be examples/basics/basic/output")
args = parser.parse_args()

bproc.init()

# load the objects into the scene
objs = bproc.loader.load_obj(args.scene)

# define a light and set its location and energy level
light = bproc.types.Light()
light.set_type("POINT")
light.set_location([5, -5, 5])
light.set_energy(1000)

# define the camera resolution
bproc.camera.set_resolution(512, 512)

# Move here
bproc.renderer.enable_normals_output()

# read the camera positions file and convert into homogeneous camera-world transformation
with open(args.camera, "r") as f:
    for line in f.readlines():
        line = [float(x) for x in line.split()]
        position, euler_rotation = line[:3], line[3:6]
        matrix_world = bproc.math.build_transformation_mat(position, euler_rotation)
        bproc.camera.add_camera_pose(matrix_world)

# activate normal and depth rendering
# bproc.renderer.enable_normals_output()
bproc.renderer.enable_depth_output(activate_antialiasing=False)

# render the whole pipeline
data = bproc.renderer.render()

# write the data to a .hdf5 container
bproc.writer.write_hdf5(args.output_dir, data)

Files required to run the code

No response

Expected behavior

I simply modify the examples in examples/basics/basic/main.py by changing bproc.renderer.enable_normals_output(). The output of the normals rendering will be blank, while the original one's output is good.

BlenderProc version

Github main branch

[cornerfarmer]

Indeed the enable_normals_output needs to know the camera poses, such that normals can be transformed into the camera frame. You are right this should be better documented.