Roughness

거칠기

A 0–1 value for how smooth a surface is: 0 gives mirror-sharp reflections, 1 spreads light like chalk.

Also known as: Roughnessinputs['Roughness']
···
bpy — this entry
# 같은 공에 거칠기(Roughness)만 0.05 → 0.4 → 0.9 로 바꿔 세 번 찍는다.
reset('EEVEE', samples=32)
camera((0, -6, 2.2), target=(0, 0, 0.9), lens=60)
floor()
hdri('studio', strength=0.8)             # 반사에 비칠 주변 — 매끈할수록 또렷하게 보인다
light('AREA', (3, -3, 5), energy=500, size=2)

bpy.ops.mesh.primitive_uv_sphere_add(segments=64, ring_count=32, radius=0.9, location=(0, 0, 0.9))
ball = bpy.context.object
bpy.ops.object.shade_smooth()
mat = material('Ball', SKY, roughness=0.05, metallic=0.0)
paint(ball, mat)
bsdf = mat.node_tree.nodes['Principled BSDF']

for value in (0.05, 0.4, 0.9):
    bsdf.inputs['Roughness'].default_value = value   # 0 = 거울처럼 매끈, 1 = 분필처럼 퍼진다
    shoot(f'r{int(value * 100):02d}')
Full script — runs as-is in Blender 5.1.1
# roughness — Blender 5.1.1 에서 그대로 돌아가는 스크립트
# 실행: blender -b --factory-startup --python roughness.py -- <출력 폴더>
SLUG = 'roughness'

# ── 무대: 모든 항목이 같이 쓰는 준비 코드 (renders/_stage.py) ──────────────────
# 빈 장면 → 렌더 엔진·크기 → 카메라·바닥·조명·재질 도우미 → shoot() 으로 WebP 저장.
import bpy, math, os, sys
from mathutils import Vector

# 출력 폴더: blender -b --factory-startup --python 이파일.py -- <출력 폴더>
OUT = sys.argv[sys.argv.index('--') + 1] if '--' in sys.argv[:-1] else os.getcwd()
os.makedirs(OUT, exist_ok=True)

# 색은 화면에서 고르는 sRGB 0~1 값으로 적는다. 블렌더 내부는 선형(linear)이라 srgb() 로 바꿔 넣는다.
BACKDROP = (0.24, 0.25, 0.27)
CLAY = (0.80, 0.77, 0.72)
LIME = (0.64, 0.90, 0.21)
SKY = (0.22, 0.65, 0.95)
CORAL = (0.96, 0.42, 0.45)
INK = (0.08, 0.09, 0.10)
ENGINES = {'WORKBENCH': 'BLENDER_WORKBENCH', 'EEVEE': 'BLENDER_EEVEE', 'CYCLES': 'CYCLES'}


def srgb(c, alpha=1.0):
    lin = lambda v: v / 12.92 if v <= 0.04045 else ((v + 0.055) / 1.055) ** 2.4
    return (lin(c[0]), lin(c[1]), lin(c[2]), alpha)


def reset(engine='WORKBENCH', samples=16, size=(960, 600)):
    """빈 장면에서 시작한다. engine: WORKBENCH(모양 확인) · EEVEE(실시간) · CYCLES(경로 추적)."""
    bpy.ops.wm.read_factory_settings(use_empty=True)
    sc = bpy.context.scene
    sc.render.engine = ENGINES[engine]
    sc.render.resolution_x, sc.render.resolution_y = size
    sc.render.resolution_percentage = 100
    sc.render.image_settings.file_format = 'WEBP'
    sc.render.image_settings.quality = 82
    sc.world = bpy.data.worlds.new('World')
    world_color(BACKDROP)
    if engine == 'WORKBENCH':
        sh = sc.display.shading
        sh.light, sh.color_type = 'STUDIO', 'MATERIAL'
        sh.show_shadows, sh.shadow_intensity = True, 0.35
        sh.show_cavity = True
        sc.display.render_aa = '16'
        sc.view_settings.view_transform = 'Standard'  # 재질 색을 그대로 보여 준다
    elif engine == 'EEVEE':
        sc.eevee.taa_render_samples = samples
    else:
        sc.cycles.samples = samples
        sc.cycles.use_denoising = True
    return sc


def world_color(color, strength=1.0):
    """배경색. Workbench 는 world.color, EEVEE·Cycles 는 Background 노드를 쓴다."""
    w = bpy.context.scene.world
    w.color = srgb(color)[:3]
    bg = w.node_tree.nodes.get('Background') if w.node_tree else None
    if bg:
        bg.inputs['Color'].default_value = srgb(color)
        bg.inputs['Strength'].default_value = strength
    return w


def hdri(name='studio', strength=1.0, show=False):
    """블렌더에 들어 있는 HDRI 로 장면을 비춘다(CC0 · Poly Haven). name: studio · city · courtyard · forest · interior · night · sunrise · sunset.
    show=False 면 빛과 반사에만 쓰고, 카메라에는 BACKDROP 색 배경이 보인다(Light Path 의 Is Camera Ray 로 가른다)."""
    nt = bpy.context.scene.world.node_tree
    nodes, links = nt.nodes, nt.links
    env = nodes.new('ShaderNodeTexEnvironment')
    env.image = bpy.data.images.load(os.path.join(bpy.utils.system_resource('DATAFILES'), 'studiolights', 'world', f'{name}.exr'))
    bg = nodes['Background']
    bg.inputs['Strength'].default_value = strength
    links.new(env.outputs['Color'], bg.inputs['Color'])
    if not show:
        flat = nodes.new('ShaderNodeBackground')
        flat.inputs['Color'].default_value = srgb(BACKDROP)
        ray, mix = nodes.new('ShaderNodeLightPath'), nodes.new('ShaderNodeMixShader')
        links.new(ray.outputs['Is Camera Ray'], mix.inputs['Fac'])
        links.new(bg.outputs['Background'], mix.inputs[1])
        links.new(flat.outputs['Background'], mix.inputs[2])
        links.new(mix.outputs['Shader'], nodes['World Output'].inputs['Surface'])
    return env


def look_at(obj, target):
    obj.rotation_euler = (Vector(target) - obj.location).to_track_quat('-Z', 'Y').to_euler()


def camera(location=(7, -7, 5), target=(0, 0, 0.5), lens=50):
    cam = bpy.data.objects.new('Camera', bpy.data.cameras.new('Camera'))
    bpy.context.scene.collection.objects.link(cam)
    cam.location = location
    look_at(cam, target)
    cam.data.lens = lens
    bpy.context.scene.camera = cam
    return cam


def frame(*objs, margin=1.15):
    """카메라 방향은 그대로 두고, objs 가 화면에 다 들어오게 카메라를 앞뒤로 옮긴다."""
    sc = bpy.context.scene
    dg = bpy.context.evaluated_depsgraph_get()
    pts = [o.matrix_world @ Vector(c) for o in objs for c in o.evaluated_get(dg).bound_box]
    mid = sum(pts, Vector()) / len(pts)
    coords = [c for p in pts for c in (mid + (p - mid) * margin)]
    loc, _scale = sc.camera.camera_fit_coords(dg, coords)
    sc.camera.location = loc
    return sc.camera


def light(kind='AREA', location=(4, -4, 6), target=(0, 0, 0), energy=600, size=3.0, color=(1, 1, 1)):
    """kind: POINT · SUN · SPOT · AREA. energy 는 와트(SUN 은 W/m²에 해당하는 세기)."""
    data = bpy.data.lights.new(kind.title(), kind)
    data.energy, data.color = energy, color
    if kind == 'AREA':
        data.size = size
    obj = bpy.data.objects.new(data.name, data)
    bpy.context.scene.collection.objects.link(obj)
    obj.location = location
    look_at(obj, target)
    return obj


def studio(key=700, fill=200, rim=450):
    """기본 3점 조명(키·필·림). EEVEE·Cycles 용 — Workbench 는 자체 스튜디오 조명을 쓴다."""
    return [light('AREA', (5, -4, 6), energy=key, size=4),
            light('AREA', (-6, -3, 3), energy=fill, size=5),
            light('AREA', (0, 6, 5), energy=rim, size=3)]


def material(name, color=CLAY, roughness=0.5, metallic=0.0, **inputs):
    """원리 BSDF 재질. inputs 는 소켓 이름(공백은 _ 로): Emission_Strength=3."""
    mat = bpy.data.materials.new(name)
    mat.diffuse_color = srgb(color)  # Workbench 가 보는 색
    bsdf = mat.node_tree.nodes['Principled BSDF']
    bsdf.inputs['Base Color'].default_value = srgb(color)
    bsdf.inputs['Roughness'].default_value = roughness
    bsdf.inputs['Metallic'].default_value = metallic
    for key, value in inputs.items():
        bsdf.inputs[key.replace('_', ' ')].default_value = value
    return mat


def paint(obj, mat):
    obj.data.materials.clear()
    obj.data.materials.append(mat)
    return obj


def floor(size=80.0, color=None, z=0.0, wall=30.0, curve=6.0):
    """바닥과 뒷벽(+Y 쪽)이 둥글게 이어진 스튜디오 배경 — 지평선이 보이지 않는다. 카메라는 -Y 쪽에서 +Y 를 보게 둔다."""
    import bmesh
    back = size / 2
    steps = 12
    profile = [(-back, 0.0)]  # (y, z) 단면: 앞 → 둥근 모서리 → 벽 위
    for i in range(steps + 1):
        a = (math.pi / 2) * i / steps
        profile.append((back - curve + curve * math.sin(a), curve - curve * math.cos(a)))
    profile.append((back, wall))
    bm = bmesh.new()
    left = [bm.verts.new((-back, y, z + h)) for y, h in profile]
    right = [bm.verts.new((back, y, z + h)) for y, h in profile]
    for i in range(len(profile) - 1):
        bm.faces.new((left[i], right[i], right[i + 1], left[i + 1]))
    me = bpy.data.meshes.new('Floor')
    bm.to_mesh(me)
    bm.free()
    obj = bpy.data.objects.new('Floor', me)
    bpy.context.scene.collection.objects.link(obj)
    for poly in me.polygons:
        poly.use_smooth = True
    return paint(obj, material('Floor', color or BACKDROP, roughness=0.9))


def edges(obj, thickness=0.012, color=INK):
    """메시의 선(엣지)을 렌더에 보이게 한다 — 모디파이어까지 적용된 모양에 와이어프레임을 씌운 복제본."""
    dg = bpy.context.evaluated_depsgraph_get()
    wire = bpy.data.objects.new(obj.name + '.edges', bpy.data.meshes.new_from_object(obj.evaluated_get(dg)))
    bpy.context.scene.collection.objects.link(wire)
    wire.matrix_world = obj.matrix_world.copy()
    mod = wire.modifiers.new('Wireframe', 'WIREFRAME')
    mod.thickness, mod.use_even_offset = thickness, True
    return paint(wire, material(obj.name + '.edges', color, roughness=0.8))


def shoot(name):
    """지금 장면을 <출력 폴더>/<항목>-<name>.webp 로 렌더한다."""
    sc = bpy.context.scene
    sc.render.filepath = os.path.join(OUT, f'{SLUG}-{name}.webp')
    bpy.ops.render.render(write_still=True)
    return sc.render.filepath


# ── 이 항목 ──
# 같은 공에 거칠기(Roughness)만 0.05 → 0.4 → 0.9 로 바꿔 세 번 찍는다.
reset('EEVEE', samples=32)
camera((0, -6, 2.2), target=(0, 0, 0.9), lens=60)
floor()
hdri('studio', strength=0.8)             # 반사에 비칠 주변 — 매끈할수록 또렷하게 보인다
light('AREA', (3, -3, 5), energy=500, size=2)

bpy.ops.mesh.primitive_uv_sphere_add(segments=64, ring_count=32, radius=0.9, location=(0, 0, 0.9))
ball = bpy.context.object
bpy.ops.object.shade_smooth()
mat = material('Ball', SKY, roughness=0.05, metallic=0.0)
paint(ball, mat)
bsdf = mat.node_tree.nodes['Principled BSDF']

for value in (0.05, 0.4, 0.9):
    bsdf.inputs['Roughness'].default_value = value   # 0 = 거울처럼 매끈, 1 = 분필처럼 퍼진다
    shoot(f'r{int(value * 100):02d}')

A pool ball, a rubber ball and a stick of chalk can share a color and still return light differently. Roughness folds the amount of microscopic bumpiness into one number. Low values keep reflections in one direction, so the surroundings (a studio HDRI here) show up crisp; higher values scatter them, so highlights grow wide and soft. In the UI: Properties editor ▸ Material tab ▸ Surface ▸ Principled BSDF ▸ Roughness.

In code you find the Principled BSDF node and set its input socket: mat.node_tree.nodes['Principled BSDF'].inputs['Roughness'].default_value = 0.4. In Blender 5.x materials always use nodes, so mat.use_nodes = True is unnecessary (it warns that the property goes away in 6.0). To paint the value with an image or noise, connect a texture node's output to this socket with links.new.

Roughness changes the shape of reflections, not the color. If you see no highlight, check that there is something to reflect (lights, an HDRI) before lowering roughness — on a pure black world even 0 shows nothing.

When to use

After color, this is the first value to tune when a surface should read as plastic, rubber or metal. Fingerprints and scratches go in as a roughness texture.

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