Mysterious Perimeter and Overhangs appear with Arachne

[MartinMajewski]

Description of the bug

Printing features that are in the range of two perimeters printed only (no infill needed, the wall-thickness is only two perimeters), mysterious glitches appear. These glitches show as perimeters and overhanging perimeters where none should be.

I have attached pictures of the object and the sliced result.

Project file & How to reproduce

IssuesWithMysteriousPerimeters.3mf.zip

Please find attached the project file.

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

2.5.0 - Release Version

Operating system

macOS 12.5.1

Printer model

Prusa MK3S

[MartinMajewski]

Btw.: this glitch appears as shown in the screenshots with the 0.6mm nozzle profile. Changing the nozzle profile to 0.4mm just changes the expression of the glitches but does not remove them.

[MartinMajewski]

Here is the wrongly produced gcode (on a newer version of the model):

[hejllukas]

Thank you for reporting this issue. Your issue is caused by an issue in the Boost Voronoi diagram generator library that Arachne uses. The boost Voronoi diagram generator is producing a non-planar Voronoi diagram that isn't correct.
It should happen only in very rare cases, but we are investigating this issue.

For now, you can workaround this issue by any of those two workarounds:

• Slightly rotate (1° is enough) the model around the Z axis.
• Change Perimeter generator settings from Arachne to Classic (The model will be sliced in the same way as in 2.4.2).

The G-code line that you mentioned is correct. G-code specification allows instead of -0.05 to produce just -.05, and printers process it correctly. We started emitting those G-code lines in PrusaSlicer 2.4.0 release.

[benkrejci]

Here's an extreme example which I assume is caused by the same thing:

Rotation by 1° did solve it for me!

If you want to test with it, here's the file:
120mmFanDesiccant.zip

Default prusament petg profile
Default prusa mini+ 0.6mm nozzle profile
Default settings with arachne

PrusaSlicer
Version: 2.5.0+win64
Build: PrusaSlicer-2.5.0+win64-202209060714

Operating System: Windows
System Architecture: 64 bit
Windows Version: Windows 10 (build 19044), 64-bit edition
Total RAM size [MB]: 34,301MB
OpenGL installation
GL version: 4.6.0 NVIDIA 516.59
Vendor: NVIDIA Corporation
Renderer: NVIDIA GeForce RTX 3070 Ti/PCIe/SSE2
GLSL version: 4.60 NVIDIA

Installed extensions:

GL_AMD_multi_draw_indirect GL_AMD_seamless_cubemap_per_texture GL_AMD_vertex_shader_layer GL_AMD_vertex_shader_viewport_index GL_ARB_ES2_compatibility GL_ARB_ES3_1_compatibility GL_ARB_ES3_2_compatibility GL_ARB_ES3_compatibility GL_ARB_arrays_of_arrays GL_ARB_base_instance GL_ARB_bindless_texture GL_ARB_blend_func_extended GL_ARB_buffer_storage GL_ARB_clear_buffer_object GL_ARB_clear_texture GL_ARB_clip_control GL_ARB_color_buffer_float GL_ARB_compatibility GL_ARB_compressed_texture_pixel_storage GL_ARB_compute_shader GL_ARB_compute_variable_group_size GL_ARB_conditional_render_inverted GL_ARB_conservative_depth GL_ARB_copy_buffer GL_ARB_copy_image GL_ARB_cull_distance GL_ARB_debug_output GL_ARB_depth_buffer_float GL_ARB_depth_clamp GL_ARB_depth_texture GL_ARB_derivative_control GL_ARB_direct_state_access GL_ARB_draw_buffers GL_ARB_draw_buffers_blend GL_ARB_draw_elements_base_vertex GL_ARB_draw_indirect GL_ARB_draw_instanced GL_ARB_enhanced_layouts GL_ARB_explicit_attrib_location GL_ARB_explicit_uniform_location GL_ARB_fragment_coord_conventions GL_ARB_fragment_layer_viewport GL_ARB_fragment_program GL_ARB_fragment_program_shadow GL_ARB_fragment_shader GL_ARB_fragment_shader_interlock GL_ARB_framebuffer_no_attachments GL_ARB_framebuffer_object GL_ARB_framebuffer_sRGB GL_ARB_geometry_shader4 GL_ARB_get_program_binary GL_ARB_get_texture_sub_image GL_ARB_gl_spirv GL_ARB_gpu_shader5 GL_ARB_gpu_shader_fp64 GL_ARB_gpu_shader_int64 GL_ARB_half_float_pixel GL_ARB_half_float_vertex GL_ARB_imaging GL_ARB_indirect_parameters GL_ARB_instanced_arrays GL_ARB_internalformat_query GL_ARB_internalformat_query2 GL_ARB_invalidate_subdata GL_ARB_map_buffer_alignment GL_ARB_map_buffer_range GL_ARB_multi_bind GL_ARB_multi_draw_indirect GL_ARB_multisample GL_ARB_multitexture GL_ARB_occlusion_query GL_ARB_occlusion_query2 GL_ARB_parallel_shader_compile GL_ARB_pipeline_statistics_query GL_ARB_pixel_buffer_object GL_ARB_point_parameters GL_ARB_point_sprite GL_ARB_polygon_offset_clamp 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GL_EXT_framebuffer_multisample_blit_scaled GL_EXT_framebuffer_object GL_EXT_framebuffer_sRGB GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters GL_EXT_gpu_shader4 GL_EXT_import_sync_object GL_EXT_memory_object GL_EXT_memory_object_win32 GL_EXT_multi_draw_arrays GL_EXT_multiview_texture_multisample GL_EXT_multiview_timer_query GL_EXT_packed_depth_stencil GL_EXT_packed_float GL_EXT_packed_pixels GL_EXT_pixel_buffer_object GL_EXT_point_parameters GL_EXT_polygon_offset_clamp GL_EXT_post_depth_coverage GL_EXT_provoking_vertex GL_EXT_raster_multisample GL_EXT_rescale_normal GL_EXT_secondary_color GL_EXT_semaphore GL_EXT_semaphore_win32 GL_EXT_separate_shader_objects GL_EXT_separate_specular_color GL_EXT_shader_image_load_formatted GL_EXT_shader_image_load_store GL_EXT_shader_integer_mix GL_EXT_shadow_funcs GL_EXT_sparse_texture2 GL_EXT_stencil_two_side GL_EXT_stencil_wrap GL_EXT_texture3D GL_EXT_texture_array GL_EXT_texture_buffer_object GL_EXT_texture_compression_dxt1 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[garethky]

+1, spotted this in one of my parts with x/y planar "thin" walls. Its producing infill in these areas and then producing strange perimeters that exit the model on top of the infill. Subscribed.

Sorting Box Support Rails.3mf.zip

[kubispe1]

These problems related to the Voronoi diagram generator are fixed in the next release 2.6.0. Here, I attach pictures and close the GH issue as resolved.