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LineArt wrong intersection detection on scene collections containing intersecting object #104562

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opened 2023-02-10 12:07:25 +01:00 by Ivan Cappiello · 8 comments
Ivan Cappiello commented 2023-02-10 12:07:25 +01:00
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System Information
Operating system: macOS-13.1-arm64-arm-64bit 64 Bits
Graphics card: Apple M1 Max Apple 4.1 Metal - 83

Blender Version
Broken: version: 3.3.3, branch: master, commit date: 2023-01-17 08:40, hash: rB8d94aeb604fa
Worked: N.A.

Short description of error
LineArt always create intersection lines if in the scene there is a collection that includes intersecting objects.

Exact steps for others to reproduce the error
open the attached lineart_intersection.blend. The file containss 2 collections:

  1. no_lineart - includes a suzanne and torus.
  2. lineart - includes just the default cube

A LineArt is created from lineart collection, even if the other collection is not involed, its intersections are incorrectly drawn on in the LineArt.

**System Information** Operating system: macOS-13.1-arm64-arm-64bit 64 Bits Graphics card: Apple M1 Max Apple 4.1 Metal - 83 **Blender Version** Broken: version: 3.3.3, branch: master, commit date: 2023-01-17 08:40, hash: `rB8d94aeb604fa` Worked: N.A. **Short description of error** LineArt always create intersection lines if in the scene there is a collection that includes intersecting objects. **Exact steps for others to reproduce the error** open the attached lineart_intersection.blend. The file containss 2 collections: 1. no_lineart - includes a suzanne and torus. 2. lineart - includes just the default cube A LineArt is created from lineart collection, even if the other collection is not involed, its intersections are incorrectly drawn on in the LineArt.
lineart_intersections.blend
963 KiB
LineArt_Intersections.png
896 KiB
LineArt_Intersections.png
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 labels 2023-02-10 12:07:26 +01:00
Ivan Cappiello changed title from LineArt wrong intersection detection on collections with intersecting object to LineArt wrong intersection detection on scene collections containing intersecting object 2023-02-10 12:08:19 +01:00
Ivan Cappiello commented 2023-02-10 12:32:06 +01:00
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@ChengduLittleA

@ChengduLittleA
Ivan Cappiello commented 2023-02-10 16:25:18 +01:00
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update: As a temporary workaround issue can be fixed by using Collection Masks with Exact Match option. Still not ideal since this is limited to 8 masking layers, but at least makes the LineArt workable in such situations.

update: As a temporary workaround issue can be fixed by using Collection Masks with Exact Match option. Still not ideal since this is limited to 8 masking layers, but at least makes the LineArt workable in such situations.
Germano Cavalcante commented 2023-02-10 20:42:16 +01:00
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It is indeed strange.
Those intersections in the other objects don't seem to have any relation to the objects within the set collection.
Is it the interface that is a bit misleading?

It indeed looks like a bug to me (but I could be wrong).

It is indeed strange. Those intersections in the other objects don't seem to have any relation to the objects within the set collection. Is it the interface that is a bit misleading? It indeed looks like a bug to me (but I could be wrong).
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YimingWu commented 2023-02-14 04:14:02 +01:00
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It's currently expected for LineArt to behave this way. Initially LineArt is designed to only handle triangle and its flags so when it gets into computing, individual triangles doesn't have "which collection(s) does it belong to", otherwise it will cost a lot of memory. hence there's a separate intersection flag thingy for you to specify custom filtering.

I think we can keep this issue open because it's a concern since the beginning of LineArt, we need to think of a way to make it more convenient.

A benefit of current setup is that it's easy to choose collection flags and combine them in one line art selection without having to regroup the objects into one collection, and a lot of times your scene doesn't allow that.

It's currently expected for LineArt to behave this way. Initially LineArt is designed to only handle triangle and its flags so when it gets into computing, individual triangles doesn't have "which collection(s) does it belong to", otherwise it will cost a lot of memory. hence there's a separate intersection flag thingy for you to specify custom filtering. I think we can keep this issue open because it's a concern since the beginning of LineArt, we need to think of a way to make it more convenient. A benefit of current setup is that it's easy to choose collection flags and combine them in one line art selection without having to regroup the objects into one collection, and a lot of times your scene doesn't allow that.
Ivan Cappiello commented 2023-02-14 08:20:02 +01:00
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@ChengduLittleA
this behaviour is totally unexpected from an user point if view.
adding a lineart is generally made by specifying a collection / object / scene to be used as source.

the current setup is consistent only whit the scene as source for lineart.
in the other two cases evaluating intersections from object outside the source you asked the user to specify for generating the lineart is not a good design choice imo.

in animation you most often (i would say always) want to separate linearts between character(s) and background.
the current design choice is not clear to the user and will generate by default overlapping intersections coming from any lineart in the file. this is trivial and difficult to troubleshoot. most users won't even get what's happening and why small segments and dots are drawn (apparently whitout a reason) in their frames.

i beleive that at least there should be a clear flag for that. like "use scene intersections (faster)" enabled by default.

while this is discussed i'd encourage you to at least update the manual to:

• reflect this actual limitation clearly

• better detail the supposed workflow for collection masks, since there is no actual description on how to use them other than the simple link to their existance. And since you are stating that at current time the users should use mask and filtering by default, i believe they should find at least a detailed information about how those wors.

also, if masking and filtering has to be intensively used for restricting intersections, raising collection layers to more than just 8 would be a good idea.

@ChengduLittleA this behaviour is totally unexpected from an user point if view. adding a lineart is generally made by specifying a collection / object / scene to be used as source. the current setup is consistent only whit the scene as source for lineart. in the other two cases evaluating intersections from object outside the source you asked the user to specify for generating the lineart is not a good design choice imo. in animation you most often (i would say always) want to separate linearts between character(s) and background. the current design choice is not clear to the user and will generate by default overlapping intersections coming from any lineart in the file. this is trivial and difficult to troubleshoot. most users won't even get what's happening and why small segments and dots are drawn (apparently whitout a reason) in their frames. i beleive that at least there should be a clear flag for that. like "use scene intersections (faster)" enabled by default. while this is discussed i'd encourage you to at least update the manual to: • reflect this actual limitation clearly • better detail the supposed workflow for collection masks, since there is no actual description on how to use them other than the simple link to their existance. And since you are stating that at current time the users should use mask and filtering by default, i believe they should find at least a detailed information about how those wors. also, if masking and filtering has to be intensively used for restricting intersections, raising collection layers to more than just 8 would be a good idea.
YimingWu commented 2023-02-14 09:25:52 +01:00
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i beleive that at least there should be a clear flag for that. like "use scene intersections (faster)" enabled by default.

The problem with LineArt is that it's not capable of doing intersection by collections. So I think the best way here is to show a warning label below the intersection checkbox and tell the user to use intersection masks.

I'll write up a better description for the manual. (Hopefully directly on the new gitea thingy? I heard it's much easier this way... Looks like the GIT version of the doc hasn't been migrated here yet ehh)

also, if masking and filtering has to be intensively used for restricting intersections, raising collection layers to more than just 8 would be a good idea.

Maybe I'll raise it to 16 bits. Even this will use more memory because this mask is recorded for each triangle/edge/edge-segment in the scene and this do accumulate... Another way is to directly record collection reference in the triangle, but then every edge segment needs to record a list of collections for later filtering and it's gonna be much more complex both during the computation and filtering. So if memory wise being acceptable, I can increase the flag bits to 16.

> i beleive that at least there should be a clear flag for that. like "use scene intersections (faster)" enabled by default. The problem with LineArt is that it's not capable of doing intersection by collections. So I think the best way here is to show a warning label below the intersection checkbox and tell the user to use intersection masks. I'll write up a better description for the manual. (~~Hopefully directly on the new gitea thingy? I heard it's much easier this way...~~ Looks like the GIT version of the doc hasn't been migrated here yet ehh) > also, if masking and filtering has to be intensively used for restricting intersections, raising collection layers to more than just 8 would be a good idea. Maybe I'll raise it to 16 bits. Even this will use more memory because this mask is recorded for each triangle/edge/edge-segment in the scene and this do accumulate... Another way is to directly record collection reference in the triangle, but then every edge segment needs to record a list of collections for later filtering and it's gonna be much more complex both during the computation and filtering. So if memory wise being acceptable, I can increase the flag bits to 16.
YimingWu commented 2023-02-15 06:26:28 +01:00
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Does this work #104767

Oh apparently this works

Does this work #104767 Oh apparently this works
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YimingWu commented 2024-10-10 09:03:37 +02:00
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This is a known issue in current line art, and to achieve intersection filtering, since recently we do have reports like #128386 (comment), I'll also post the solution here. You can utilize such steps to select intersection lines you wanted:

  1. You have collection A and B, you only want intersection lines within collection B
  2. Select collections A and go to Collection tab > Line Art > Collection Mask (Enable) > Set mask bit 1
  3. Select collection B and set mask bit 2
  4. In Line Art modifier > Intersection sub panel > Collection Masks:
    • If you only want intersection lines within collection B, set mask bit 2 and enable Exact Match
    • If you only want lines between A and B, set mask bit 1 and 2 and enable Exact Match

I'm not sure whether I should close this one for now, since it's indeed a known issue, but maybe I'll leave it here for future references.

This is a known issue in current line art, and to achieve intersection filtering, since recently we do have reports like https://projects.blender.org/blender/blender/issues/128386#issuecomment-1312018, I'll also post the solution here. You can utilize such steps to select intersection lines you wanted: 1. You have collection A and B, you only want intersection lines within collection B 2. Select collections A and go to Collection tab > Line Art > Collection Mask (Enable) > Set mask bit 1 3. Select collection B and set mask bit 2 4. In Line Art modifier > Intersection sub panel > Collection Masks: - If you only want intersection lines within collection B, set mask bit 2 and enable Exact Match - If you only want lines between A and B, set mask bit 1 and 2 and enable Exact Match I'm not sure whether I should close this one for now, since it's indeed a known issue, but maybe I'll leave it here for future references.
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