Prevent Scale and Rotation to affect Hair Simulation?

Support Particles and Physics Simulations
1

I have this Suzzanne with Hair that I created:

image (36)
image (36)1186×837 555 KB

And I created an animation for the monkey object that makes it appears and disappears using scaling and rotation. This is the animation in question:

The issue is that, as you can see, the rotation and mainly the scaling is causing too much of a problem to my hair:

image (37)
image (37)801×679 338 KB

I want it to look as close to the first image as possible, this is more important than having the hair physically simulated properly. So how can I fix it?

My initial idea is to figure out how to disable the object scale from influencing the hair… but how?

I’ve made a Video Explaining it:

Thanks!

2

I think parenting it to an empty and scaling that should work, while the simulation might still make some funky stuff.

1 Like
3

Thanks! So I decided to completely disable Physics… but still:

4

Then its a modifier thing. The order is very important on what gets calculated first…

But i am not even sure if its supported to scale down a mesh with hair.

5

dada
dada332×589 24.8 KB

Try to rotate in the same setting as the image.
Some of the settings in the Orientation Axis are moved, and some are fixed.

For scale issue, make Empty and connect Suzanne to Empty, and apply animation to Empty.

※ If you apply rotation animation to Empty, the rotation is not fixed.

6

Hi, y’all! thanks for the replies!

I don’t have any modifiers other than the Particle. The Rotation also didn’t changed what I described in the video. Same with applying the transforms with an empty parent instead of the object.

If I render it frame by frame, it works. If I render it as an animation, it doesn’t. Disabling Motion Blur did not change the issue too. I’ve also tried different file output formats (png, mkv, bmp, etc).

Workaround:

So I made a small script that renders the animation frame by frame manually and saves it to disk. I’ll share it here just in case anyone needs it:

import bpy
import os

# Set the output directory
output_dir = "C:/tmp/monkey/"

# Frame Range:
frame_start = 0
frame_end   = 80

os.makedirs(output_dir, exist_ok=True)

# Loop through each frame and render
for frame_num in range(frame_start, frame_end + 1):
    bpy.context.scene.frame_set(frame_num)
    bpy.ops.render.render(write_still=True)
    
    print(f"Rendering Frame {frame_num}...")

    # Saving the rendered image...
    frame_num_str = str(frame_num).zfill(2)
    file_path = os.path.join(output_dir, f"{frame_num_str}.png")
    bpy.data.images['Render Result'].save_render(filepath=file_path)
1 Like