Blender Scene to LLFF data

[Robin-Zoe]

Hello! Thanks a lot for sharing your code and data. How can I convert a scene in Blender into an LLFF file? I currently have a Blender scene that I've created, similar to Classroom, and now I need to convert it into the LLFF dataset format. Could you provide some assistance?

[ug-kim]

In the Blender synthetic dataset cases, we did not use the LLFF dataset format. Rather than this, we used blender rendering code with Python, which is shared in NeRF synthetic dataset.

It is some examples with NeRF synthetic dataset, class is chair. You can find it in the scripting section of Blender.

# A simple script that uses blender to render views of a single object by rotation the camera around it.
# Also produces depth map at the same time.

import argparse, sys, os
import json
import bpy
import mathutils
import numpy as np

DEBUG = False

VIEWS = 200
RESOLUTION = 800
RESULTS_PATH = 'results_test_200'
DEPTH_SCALE = 1.4
COLOR_DEPTH = 8
FORMAT = 'PNG'
UPPER_VIEWS = True
CIRCLE_FIXED_START = (0,0,0)
CIRCLE_FIXED_END = (.7,0,0)

fp = bpy.path.abspath(f"//{RESULTS_PATH}")

def listify_matrix(matrix):
    matrix_list = []
    for row in matrix:
        matrix_list.append(list(row))
    return matrix_list

if not os.path.exists(fp):
    os.makedirs(fp)

# Data to store in JSON file
out_data = {
    'camera_angle_x': bpy.data.objects['Camera'].data.angle_x,
}

# Render Optimizations
bpy.context.scene.render.use_persistent_data = True

# Set up rendering of depth map.
bpy.context.scene.use_nodes = True
tree = bpy.context.scene.node_tree
links = tree.links

# Add passes for additionally dumping albedo and normals.
bpy.context.scene.view_layers["RenderLayer"].use_pass_normal = True
bpy.context.scene.render.image_settings.file_format = str(FORMAT)
bpy.context.scene.render.image_settings.color_depth = str(COLOR_DEPTH)

if 'Custom Outputs' not in tree.nodes:
    # Create input render layer node.
    render_layers = tree.nodes.new('CompositorNodeRLayers')
    render_layers.label = 'Custom Outputs'
    render_layers.name = 'Custom Outputs'

    depth_file_output = tree.nodes.new(type="CompositorNodeOutputFile")
    depth_file_output.label = 'Depth Output'
    depth_file_output.name = 'Depth Output'
    if FORMAT == 'OPEN_EXR':
      links.new(render_layers.outputs['Depth'], depth_file_output.inputs[0])
    else:
      # Remap as other types can not represent the full range of depth.
      map = tree.nodes.new(type="CompositorNodeMapRange")
      # Size is chosen kind of arbitrarily, try out until you're satisfied with resulting depth map.
      map.inputs['From Min'].default_value = 0
      map.inputs['From Max'].default_value = 8
      map.inputs['To Min'].default_value = 1
      map.inputs['To Max'].default_value = 0
      links.new(render_layers.outputs['Depth'], map.inputs[0])

      links.new(map.outputs[0], depth_file_output.inputs[0])

    normal_file_output = tree.nodes.new(type="CompositorNodeOutputFile")
    normal_file_output.label = 'Normal Output'
    normal_file_output.name = 'Normal Output'
    links.new(render_layers.outputs['Normal'], normal_file_output.inputs[0])

# Background
bpy.context.scene.render.dither_intensity = 0.0
bpy.context.scene.render.film_transparent = True

# Create collection for objects not to render with background

objs = [ob for ob in bpy.context.scene.objects if ob.type in ('EMPTY') and 'Empty' in ob.name]
bpy.ops.object.delete({"selected_objects": objs})

def parent_obj_to_camera(b_camera):
    origin = (0, 0, 0)
    b_empty = bpy.data.objects.new("Empty", None)
    b_empty.location = origin
    b_camera.parent = b_empty  # setup parenting

    scn = bpy.context.scene
    scn.collection.objects.link(b_empty)
    bpy.context.view_layer.objects.active = b_empty
    # scn.objects.active = b_empty
    return b_empty

scene = bpy.context.scene
scene.render.resolution_x = RESOLUTION
scene.render.resolution_y = RESOLUTION
scene.render.resolution_percentage = 100

cam = scene.objects['Camera']
cam.location = (0, 4.0, 0.5)
cam_constraint = cam.constraints.new(type='TRACK_TO')
cam_constraint.track_axis = 'TRACK_NEGATIVE_Z'
cam_constraint.up_axis = 'UP_Y'
b_empty = parent_obj_to_camera(cam)
cam_constraint.target = b_empty

scene.render.image_settings.file_format = 'PNG'  # set output format to .png

from math import radians

stepsize = 360.0 / VIEWS
vertical_diff = CIRCLE_FIXED_END[0] - CIRCLE_FIXED_START[0]
rotation_mode = 'XYZ'

if not DEBUG:
    for output_node in [tree.nodes['Depth Output'], tree.nodes['Normal Output']]:
        output_node.base_path = ''

out_data['frames'] = []

b_empty.rotation_euler = CIRCLE_FIXED_START[0] + vertical_diff

for i in range(0, VIEWS):
    if DEBUG:
        i = np.random.randint(0,VIEWS)
        b_empty.rotation_euler[0] = CIRCLE_FIXED_START[0] + (np.cos(radians(stepsize*i))+1)/2 * vertical_diff
        b_empty.rotation_euler[2] += radians(2*stepsize*i)

    print("Rotation {}, {}".format((stepsize * i), radians(stepsize * i)))
    scene.render.filepath = fp + '/r_' + str(i)

    tree.nodes['Depth Output'].file_slots[0].path = scene.render.filepath + "_depth_"
    tree.nodes['Normal Output'].file_slots[0].path = scene.render.filepath + "_normal_"

    if DEBUG:
        break
    else:
        bpy.ops.render.render(write_still=True)  # render still

    frame_data = {
        'file_path': scene.render.filepath,
        'rotation': radians(stepsize),
        'transform_matrix': listify_matrix(cam.matrix_world)
    }
    out_data['frames'].append(frame_data)

    b_empty.rotation_euler[0] = CIRCLE_FIXED_START[0] + (np.cos(radians(stepsize*i))+1)/2 * vertical_diff
    b_empty.rotation_euler[2] += radians(2*stepsize)

if not DEBUG:
    with open(fp + '/' + 'transforms.json', 'w') as out_file:
        json.dump(out_data, out_file, indent=4)

[Robin-Zoe]

Thank you very much for your reply! However, what I meant is similar to the datasets you provided, such as book, kitchen, monk, room data. These data are in LLFF format and have corresponding .blender files. What I'm asking is how to convert these .blender files into LLFF format datasets.