manim-020-gotchas

name	manim-020-gotchas
title	Manim CE 0.20.1 Common Pitfalls
description	Gotchas and API changes specific to Manim Community Edition 0.20.1. Includes ImageMobject, animation names, and font handling.
author	Hermi
date	2026-04-16T00:00:00.000Z
tags	["manim","animation","gotchas",0.2]

Overview

Common pitfalls discovered when building Manim animations with CE v0.20.1. Prevents runtime errors during render.

Pitfalls & Fixes

1. ImageMobject cannot go in VGroup

# WRONG — raises TypeError

## When to Use
Gotchas and API changes specific to Manim Community Edition 0.20.1. Includes ImageMobject, animation names, and font handling.

VGroup(title, ImageMobject("plot.png"), caption)

# CORRECT — use Group instead
Group(title, ImageMobject("plot.png"), caption)

VGroup only accepts VMobject subclasses. ImageMobject is a PixelArtMobject, not a VMobject. Use Group (which accepts any Mobject) when mixing images with text/shapes.

2. GrowIn does not exist in 0.20.1

Available animation aliases for images:

• FadeIn(mob) — fade from transparent
• FadeOut(mob) — fade to transparent
• GrowFromPoint(mob, point) — grow from a specific point
• GrowFromCenter(mob) — grow from center

GrowIn was removed/renamed. Use FadeIn for image appearances.

3. Font name fallback

Manim 0.20.1 warns if a requested font is not installed. Common fallback:

# Instead of font="Courier" (may warn)
font="DejaVu Sans Mono"  # usually available

# Or use default (no font= parameter, uses DejaVu Sans)
Text("Hello")  # Uses default sans-serif

4. partial_movie_files cache corruption

If a render crashes mid-way, the next render may use corrupted cached animations. Fix: delete the specific partial file or the whole cache:

rm -rf media/videos/*/partial_movie_files/SCENE_NAME/

5. run_time vs wait for scene pacing

Use explicit wait() between animated sections instead of inflating run_time on the last animation — wait() is more predictable and easier to debug timing:

self.play(Write(text), run_time=2.0)
self.wait(2.0)  # clear separation of animation and reading time

6. Random state in animations

If using np.random in animation loops, seed it at the scene level:

def construct(self):
    np.random.seed(42)  # reproducible star positions, etc.

7. ParametricFunction uses t_range, NOT t_min/t_max

# WRONG — raises TypeError: Mobject.__init__() got an unexpected keyword argument 't_min'
ParametricFunction(
    lambda t: np.array([t, np.sin(t), 0]),
    t_min=-PI, t_max=PI, color=GREEN
)

# CORRECT — tuple of (min, max, step)
ParametricFunction(
    lambda t: np.array([t, np.sin(t), 0]),
    t_range=(-PI, PI, 0.05),
    color=GREEN
)

8. MathTex does NOT accept font or font_size parameters

# WRONG — raises TypeError: Mobject.__init__() got an unexpected keyword argument 'font'
MathTex(r"\frac{a}{b}", font="DejaVu Sans Mono", font_size=30)

# CORRECT — use .scale() for sizing
formula = MathTex(r"\frac{a}{b}")
formula.scale(0.8)

MathTex inherits from SVG objects — it uses system LaTeX fonts. For custom fonts/size, use Text() instead.

9. MathTex.get_part_by_tex() often returns None

# WRONG — may return None, then .set_color() crashes
eq.get_part_by_tex("sin(\\theta)").set_color(GREEN)
eq.get_part_by_tex("y").set_color(GREEN)

# CORRECT — use set_color_by_tex() which searches all submobjects
eq.set_color_by_tex("sin", GREEN)
eq.set_color_by_tex("y", GREEN)
eq.set_color_by_tex("r", YELLOW)

get_part_by_tex() looks for exact tex string matches in submobjects, which often fail because Manim splits the equation into many individual submobjects. set_color_by_tex() is more reliable.

10. DOWN_RIGHT does NOT exist in Manim 0.20.1

# WRONG — raises NameError
Line(ORIGIN, DOWN_RIGHT * 2.5, color=DIM)

# CORRECT — compose from unit vectors
Line(ORIGIN, RIGHT * 2 - DOWN * 1.5, color=DIM)

Available direction shortcuts: UP, DOWN, LEFT, RIGHT, UP_LEFT, UP_RIGHT, DOWN_LEFT, DOWN_RIGHT — NONE of these exist in Manim CE. Always compose: RIGHT * 2 - DOWN * 1.5.

11. run_time(...) syntax error (function-call style)

# WRONG — run_time is a keyword argument, not a function call
self.play(Create(mob), run_time(0.3))

# CORRECT — keyword argument
self.play(Create(mob), run_time=0.3)

Common typo from copying/manually editing. Always check run_time=, not run_time(...).

12. Text() does NOT accept font_weight parameter

# WRONG — raises TypeError: unexpected keyword argument 'font_weight'
Text("Hello", font_size=44, font_weight=8)

# CORRECT — no font_weight
Text("Hello", font_size=44)

Manim 0.20.1's Text class (Pango-based) does not support font_weight. For bold text, use Text("Hello", font="DejaVu Sans Bold") or just rely on default rendering.

13. Arc does NOT accept start_position parameter

# WRONG — raises TypeError: unexpected keyword argument 'start_position'
Arc(radius=0.5, start_angle=0, angle=theta, start_position=LEFT * 3)

# CORRECT — use .add_updater() or .move_to() to position
arc = Arc(radius=0.5, start_angle=0, angle=theta)
arc.add_updater(lambda m: m.move_to(LEFT * 3))
# OR just create it at the right position after creation

The start_position parameter is not part of Manim CE's Arc API. Use move_to() or an updater to position.

14. Frame rate limits minimum wait() duration

# At 15 FPS, self.wait(0.03) → Manim warns and uses 0.067s minimum
self.wait(0.03)  # WARNING: too short for current frame rate

# At 60 FPS (high quality render), self.wait(0.03) works fine

Low-quality draft renders (-ql) use 15 FPS, so wait() under ~0.067s gets silently extended. High-quality renders (-qh) use 60 FPS where 0.03s is fine. Design animations assuming -ql pacing if you want draft renders to look correct.

15. MathTex does NOT accept color in .scale()

# WRONG — raises TypeError: unexpected keyword argument 'color'
MathTex("+", color=RED).scale(0.6, color=RED)

# CORRECT — set color in constructor OR use .set_color()
MathTex("+", color=RED).scale(0.6)
# OR
MathTex("+").scale(0.6).set_color(RED)

.scale() only accepts sizing arguments. Pass color= to the constructor, or call .set_color() after scaling.

16. CYAN does NOT exist in Manim 0.20.1

# WRONG — raises NameError: name 'CYAN' is not defined
Text("minus", color=CYAN)

# CORRECT — use TEAL, TEAL_A..E, or PURE_CYAN
Text("minus", color=TEAL)
# OR
Text("minus", color=PURE_CYAN)

Check available color names with: python3 -c "from manim import *; print(dir())" | tr ',' '\n' | grep -iE "cyan|teal|blue"

17. Unicode minus − (U+2212) crashes MathTex LaTeX compilation

# WRONG — raises ValueError: latex error converting to dvi
#          "! LaTeX Error: Unicode character − (U+2212) not set up for use with LaTeX."
MathTex(r"−", color=WHITE)

# CORRECT — use plain ASCII dash, or use Text() instead
MathTex(r"-", color=WHITE)
# OR
Text("-", color=WHITE)

MathTex goes through LaTeX which has no Unicode minus support. Use ASCII "-" in MathTex, or use Text() (Pango-based, no LaTeX) for arbitrary Unicode characters.

18. Arrow does NOT accept tip_width_factor

# WRONG — raises TypeError: unexpected keyword argument 'tip_width_factor'
Arrow(start, end, tip_width_factor=0.4)

# CORRECT — use max_tip_length_to_length_ratio and stroke_width
Arrow(start, end, stroke_width=5, max_tip_length_to_length_ratio=0.3)

Check Arrow's signature: python3 -c "from manim import Arrow; import inspect; print(inspect.signature(Arrow.__init__))" Relevant params: stroke_width, buff, max_tip_length_to_length_ratio, max_stroke_width_to_length_ratio.

Verification Checklist

• ImageMobject in Group, not VGroup
• FadeIn instead of GrowIn
• Fonts exist on system (check with fc-list | grep fontname)
• Partial cache cleaned after any crash
• wait() calls between major sections
• np.random.seed() set for reproducible elements
• color= in constructor, NOT in .scale()
• TEAL/PURE_CYAN not CYAN
• ASCII "-" in MathTex(), use Text() for Unicode
• max_tip_length_to_length_ratio not tip_width_factor in Arrow()
• No Polyline — use VGroup of Line segments
• No side_length on Triangle — use .scale() after creation
• VGroup() already groups, no need to wrap again

Additional Pitfalls

19. Polyline does NOT exist in Manim 0.20.1

# WRONG — raises NameError: name 'Polyline' is not defined
Polyline(points, color=GREEN, stroke_width=4)

# CORRECT — use VGroup of Line segments
segments = VGroup()
for i in range(len(points)-1):
    segments.add(Line(points[i], points[i+1], color=GREEN, stroke_width=4))

For zigzag resistors or any polyline, build it from individual Line objects in a VGroup.

20. Triangle(side_length=...) is NOT supported

# WRONG — raises TypeError: unexpected keyword argument 'side_length'
Triangle(side_length=0.3, color=RED)

# CORRECT — create and scale, or use Dot/regular polygon
Triangle().scale(0.15).set_color(RED)
# OR
Dot(radius=0.15, color=RED, fill_opacity=0.8)

Triangle (which is a RegularPolygram) only accepts **kwargs for styling. For triangles use .scale() after creation. For LED-like indicators, Dot is often simpler.

21. VGroup unpacking confusion

# WRONG — VGroup already takes items, not unpacked list
wires = VGroup(L1, L2, L3, L4)
self.play(Create(v_group(*wires)))  # 'v_group' undefined, and * doesn't apply here

# CORRECT
wires = VGroup(L1, L2, L3, L4)
self.play(Create(wires))

VGroup() takes items directly as arguments. There is no v_group() — it's VGroup. And wires is already a single Mobject, so just pass wires, not *wires.

22. Arrow stroke_width affects both line and arrowhead

If you want a thick line but proportional arrowhead, use stroke_width together with max_tip_length_to_length_ratio. The stroke_width sets both the shaft and the arrowhead bar thickness.

23. set_color_by_tex() on a copy doesn't affect original

# WRONG — modifying the copy doesn't highlight the original
formula_red = formula.copy()
formula_red.set_color_by_tex("V", RED)
# formula is still yellow!

# CORRECT — modify in place or re-render with the colored version
formula.set_color_by_tex("V", RED)

When highlighting parts of a MathTex, either call set_color_by_tex() on the original or use the copy for the entire animation replacing the original.

25. tip_width_ratio does NOT exist on Arrow()

# WRONG — raises TypeError: unexpected keyword argument 'tip_width_ratio'
Arrow(start, end, tip_width_ratio=0.3)

# CORRECT — Arrow supports these tip-related params:
#   stroke_width, buff, tip_length, max_tip_length_to_length_ratio,
#   max_stroke_width_to_length_ratio
Arrow(start, end, stroke_width=4, max_tip_length_to_length_ratio=0.3)

tip_width_ratio is NOT a valid Arrow parameter in Manim CE. The closest alternatives are max_tip_length_to_length_ratio and tip_length. See also pitfall 18 (tip_width_factor also invalid).

26. Degenerate Arrow (start == end) crashes deep in numpy

# WRONG — start and end are the same point, crashes with
#        ValueError: At least one array has zero dimension
line = DashedLine(ORIGIN, ORIGIN, color=DIM)
# OR
line = Arrow(P, P, color=DIM)  # P is any Mobject position

# CORRECT — ensure start != end
# Use a non-zero distance, or use a different mobject entirely
line = Line(ORIGIN, RIGHT * 0.1, color=DIM, stroke_width=1.5)

When start and end are identical, Arrow.put_start_and_end_on() calls np.cross(zero_vector, zero_vector) which raises. Even DashedLine(ORIGIN, ORIGIN) crashes. If you need a zero-length decorative element, use Dot() or a short Line() instead.

27. FadeOut(Group(...)) can crash with assertion errors

# WRONG — may crash: AssertionError in updater
self.play(FadeOut(Group(mob1, mob2, mob3)))

# CORRECT — fade individually
self.play(FadeOut(mob1), FadeOut(mob2), FadeOut(mob3))
# OR use AnimationGroup
self.play(AnimationGroup(FadeOut(mob1), FadeOut(mob2), FadeOut(mob3)))

FadeOut on a Group can trigger assertion errors inside Manim's updater system, especially when the group contains mobjects with conflicting states. Fade individual mobjects or use AnimationGroup instead.

24. Axes.get_tick_labels() does NOT exist

# WRONG — raises AttributeError: 'Axes' object has no attribute 'tick_labels'
x_ticks = axes.get_tick_labels()
self.play(FadeIn(x_ticks))

# CORRECT — Manim renders axis ticks by default
# No extra call needed

Manim's Axes renders tick marks and labels automatically. If you need custom tick labels, use axes.get_axis_labels() or create them manually with MathTex/Text and axes.c2p().