# Corona Edge Map

**URL:** <https://forums.chaos.com/t/corona-edge-map/157425>\
**Category:** Help Required\
**Created:** [January 26, 2024, 12:54pm UTC](https://forums.chaos.com/t/corona-edge-map/157425 "2024-01-26T12:54:08Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Blanco\_1](https://avatars.discourse-cdn.com/v4/letter/b/bb73d2/32.png) [@Blanco\_1](https://forums.chaos.com/u/Blanco_1)\
**Post date:** [January 26, 2024, 12:54pm UTC](https://forums.chaos.com/t/corona-edge-map/157425/1 "2024-01-26T12:54:08Z")

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Could someone please tell me how to use this map?  
I can only get it to work on polygons with zero thikness. It doesn’t work on an extruded spline even when height is set to zero and it definately doesn’t work on a box.  
Maybe I’m trying to use it for the wrong thing - adding dirt and streaks. I have been using the AO map but wanted to see if this was better/easier.  
Thanks

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**Author:** ![tom\_grimes](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/tom_grimes/32/52842_2.png) [@tom\_grimes](https://forums.chaos.com/u/tom_grimes)\
**Post date:** [January 26, 2024, 12:57pm UTC](https://forums.chaos.com/t/corona-edge-map/157425/2 "2024-01-26T12:57:47Z")

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That is it’s intended use, on objects with zero thickness. For boxes and enclosed geometry, CoronaAO and CoronaRoundEdges can do the same / similar thing, but those don’t work on zero thickness objects. The Edge shader is the reverse, does a similar thing on zero thickness, but not on enclosed geometry, so that there is something to cover all cases.

There’s the feature video at [https://youtu.be/KBDVq-ZLFX0](https://youtu.be/KBDVq-ZLFX0) that goes over basic usage of the shader.

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**Author:** ![Blanco\_1](https://avatars.discourse-cdn.com/v4/letter/b/bb73d2/32.png) [@Blanco\_1](https://forums.chaos.com/u/Blanco_1)\
**Post date:** [January 30, 2024, 1:39pm UTC](https://forums.chaos.com/t/corona-edge-map/157425/3 "2024-01-30T13:39:12Z")

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Ok. Thanks!

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**Author:** ![maru](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/maru/32/15975_2.png) [@maru](https://forums.chaos.com/u/maru)\
**Post date:** [January 30, 2024, 1:53pm UTC](https://forums.chaos.com/t/corona-edge-map/157425/4 "2024-01-30T13:53:30Z")

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Archviz Artist are showing a good use for it - coloring plant leaves, although the leaf borders need to be edges; opacity-mapped rectangles won’t work.  
[https://youtu.be/1bBlGsngJhM?si=PbMeQjboC022Qco1](https://youtu.be/1bBlGsngJhM?si=PbMeQjboC022Qco1)

Another idea is VFX - for example imagine that a surface is fragmented into small parts (but larger than a single polygon). You can’t use other maps there to color the borders of the fragments.

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**Author:** ![Bowcat](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@Bowcat](https://forums.chaos.com/u/Bowcat)\
**Post date:** [January 30, 2024, 4:01pm UTC](https://forums.chaos.com/t/corona-edge-map/157425/5 "2024-01-30T16:01:01Z")

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> [@maru](#):
>
> Archviz Artist are showing a good use for it - coloring plant leaves, although the leaf borders need to be edges; opacity-mapped rectangles won’t work.  
> [https://youtu.be/1bBlGsngJhM?si=PbMeQjboC022Qco1](https://youtu.be/1bBlGsngJhM?si=PbMeQjboC022Qco1)
> 
> Another idea is VFX - for example imagine that a surface is fragmented into small parts (but larger than a single polygon). You can’t use other maps there to color the borders of the fragments.

I used it with really good results to have white lines (street markings) all around streets and parking areas.