rendering/render_albedo.py

import blenderproc as bproc
import numpy as np
import os
os.environ["OPENCV_IO_ENABLE_OPENEXR"]="1"
import json
import bpy
import cv2
from PIL import Image
import math
from mathutils import Vector, Matrix
import argparse

parser = argparse.ArgumentParser()
parser.add_argument('--glb_path', type=str)
parser.add_argument('--output_dir', type=str, default='output')
args = parser.parse_args()

# load the glb model
def load_object(object_path: str) -> None:
    """Loads a glb model into the scene."""
    if object_path.endswith(".glb") or object_path.endswith(".gltf"):
        bpy.ops.import_scene.gltf(filepath=object_path, merge_vertices=False)
    elif object_path.endswith(".fbx"):
        bpy.ops.import_scene.fbx(filepath=object_path)
    elif object_path.endswith(".obj"):
        bpy.ops.import_scene.obj(filepath=object_path)
    elif object_path.endswith(".ply"):
        bpy.ops.import_mesh.ply(filepath=object_path)
    else:
        raise ValueError(f"Unsupported file type: {object_path}")


def load_envmap(envmap_path: str) -> None:
    """Loads an environment map into the scene."""
    world = bpy.context.scene.world
    world.use_nodes = True
    bg = world.node_tree.nodes['Background']
    envmap = world.node_tree.nodes.new('ShaderNodeTexEnvironment')
    envmap.image = bpy.data.images.load(envmap_path)
    world.node_tree.links.new(bg.inputs['Color'], envmap.outputs['Color'])


def turn_off_metallic():
    # use for albedo rendering, metallic will affect the color
    materials = bproc.material.collect_all()
    for mat in materials:
        mat.set_principled_shader_value('Metallic', 0.0)


def camera_pose(azimuth, elevation, radius=1.5):
    """Camera look at the origin."""
    azimuth = np.deg2rad(azimuth)
    elevation = np.deg2rad(elevation)

    x = radius * np.cos(azimuth) * np.cos(elevation)
    y = -radius * np.sin(azimuth) * np.cos(elevation)
    z = radius * np.sin(elevation)
    camera_position = np.array([x, y, z])

    camera_forward = camera_position / np.linalg.norm(camera_position)
    camera_right = np.cross(np.array([0.0, 0.0, 1.0]), camera_forward)
    camera_right /= np.linalg.norm(camera_right)
    camera_up = np.cross(camera_forward, camera_right)
    camera_up /= np.linalg.norm(camera_up)

    camera_pose = np.eye(4)
    camera_pose[:3, 0] = camera_right
    camera_pose[:3, 1] = camera_up
    camera_pose[:3, 2] = camera_forward
    camera_pose[:3, 3] = camera_position

    return camera_pose


def scene_root_objects():
    for obj in bpy.context.scene.objects.values():
        if not obj.parent:
            yield obj


def scene_meshes():
    for obj in bpy.context.scene.objects.values():
        if isinstance(obj.data, (bpy.types.Mesh)):
            yield obj


def scene_bbox(single_obj=None, ignore_matrix=False):
    bbox_min = (math.inf,) * 3
    bbox_max = (-math.inf,) * 3
    found = False
    for obj in scene_meshes() if single_obj is None else [single_obj]:
        found = True
        for coord in obj.bound_box:
            coord = Vector(coord)
            if not ignore_matrix:
                coord = obj.matrix_world @ coord
            bbox_min = tuple(min(x, y) for x, y in zip(bbox_min, coord))
            bbox_max = tuple(max(x, y) for x, y in zip(bbox_max, coord))
    if not found:
        raise RuntimeError("no objects in scene to compute bounding box for")
    return Vector(bbox_min), Vector(bbox_max)


def normalize_scene():
    bbox_min, bbox_max = scene_bbox()

    scale = 1 / max(bbox_max - bbox_min)
    for obj in scene_root_objects():
        obj.scale = obj.scale * scale
    # Apply scale to matrix_world.
    bpy.context.view_layer.update()
    bbox_min, bbox_max = scene_bbox()
    offset = -(bbox_min + bbox_max) / 2
    for obj in scene_root_objects():
        obj.matrix_world.translation += offset
    bpy.ops.object.select_all(action="DESELECT")

    return scale, offset


def reset_normal():
    """experimental!!!
    reset normal
    """
    for obj in scene_meshes():
        bpy.context.view_layer.objects.active = obj
        bpy.ops.object.mode_set(mode='EDIT')
        bpy.ops.mesh.normals_tools(mode='RESET')
        bpy.ops.object.mode_set(mode='OBJECT')


def change_to_orm():
    materials = bproc.material.collect_all()
    for mat in materials:
        orm_color = mat.nodes.new(type='ShaderNodeCombineRGB')
        principled_bsdf = mat.get_the_one_node_with_type("BsdfPrincipled")

        # metallic -> Blue
        if principled_bsdf.inputs['Metallic'].links:
            metallic_from_socket = principled_bsdf.inputs['Metallic'].links[0].from_socket
            metallic_link = mat.links.new(metallic_from_socket, orm_color.inputs['B'])
            mat.links.remove(principled_bsdf.inputs['Metallic'].links[0])
        else:
            metallic_value = principled_bsdf.inputs['Metallic'].default_value
            orm_color.inputs['B'].default_value = metallic_value
        principled_bsdf.inputs['Metallic'].default_value = 0.0
        # roughness -> Green
        if principled_bsdf.inputs['Roughness'].links:
            roughness_from_socket = principled_bsdf.inputs['Roughness'].links[0].from_socket
            roughness_link = mat.links.new(roughness_from_socket, orm_color.inputs['G'])
            mat.links.remove(principled_bsdf.inputs['Roughness'].links[0])
        else:
            roughness_value = principled_bsdf.inputs['Roughness'].default_value
            orm_color.inputs['G'].default_value = roughness_value
        principled_bsdf.inputs['Roughness'].default_value = 0.5

        # link orm_color to principled_bsdf as base color
        mat.links.new(orm_color.outputs['Image'], principled_bsdf.inputs['Base Color'])


def is_bsdf():
    for mat in bproc.material.collect_all():
        node = mat.get_nodes_with_type('BsdfPrincipled')
        if node and len(node) == 1:
            pass
        else:
            return False
    return True


def sample_sphere(num_samples):
    radiuss = np.random.uniform(1.5, 2.0, size=num_samples)
    azimuth = np.random.uniform(0, 360, size=num_samples)
    elevation = np.random.uniform(-90, 90, size=num_samples)
    return radiuss, azimuth, elevation


bproc.init()
# bproc.renderer.set_render_devices(use_only_cpu=True)
# bpy.context.scene.view_settings.view_transform = 'Raw' # do not use sRGB

glb_path = args.glb_path
output_dir = args.output_dir
obj_name = os.path.basename(glb_path).split('.')[0]
load_object(glb_path)

scale, offset = normalize_scene()

reset_normal()
turn_off_metallic()

# load camera info
with open(os.path.join(output_dir, obj_name, 'camera.json'), 'r') as f:
    meta_info = json.load(f)
radiuss = np.array(meta_info['raidus'])
azimuths = np.array(meta_info['azimuths'])
elevations = np.array(meta_info['elevations'])
# set camera
bproc.camera.set_resolution(512, 512)
for radius, azimuth, elevation in zip(radiuss, azimuths, elevations):
    cam_pose = camera_pose(azimuth, elevation, radius=radius)
    bproc.camera.add_camera_pose(cam_pose)

bproc.renderer.enable_diffuse_color_output()

bproc.renderer.set_output_format(enable_transparency=True)

data = bproc.renderer.render()

for i in range(len(azimuths)):
    image = data['diffuse'][i]
    Image.fromarray(image).save(os.path.join(output_dir, obj_name, f'albedo_{i:02d}.png'))