Author Topic: [solved] Corona Scatter Exclude areas  (Read 25424 times)

2015-09-30, 15:06:34

Torsten

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Hey Guys,

I am wondering if it is possible to also set exclude areas in Corona Scatter? I have some concrete slabs where i don't want the plants to be scattered. As you can see, the grass is now intersecting the objects. I have different corona scatter systems, so i would like to set the exclusion on all of them.

Thanks!
« Last Edit: 2015-10-08, 10:55:29 by maru »

2015-09-30, 15:08:53
Reply #1

maru

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You can either create a separate distribution object and make in non-renderable, or you can use density map to exclude that region.
Marcin Miodek | chaos-corona.com
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2015-09-30, 15:20:03
Reply #2

Torsten

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Not sure if i understand what you mean. I attached an image of the scene. I would like to make a path towards the house. The plane is the surface i scattered alle the objects on. I would like to exclude the path between the red lines. How would you do this? I tried to paint in vertex color, but i am not sure how this works, and how to use this as an exclude map.

Thanks

2015-09-30, 15:36:02
Reply #3

maru

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Here are some images.

vertex paint:
add vertex paint modifier, paint white areas that will be used for scattering, paint black areas that will be clear, then put vertex color map in the cscatter density map

cutout:
delete some of the base object's vertices/faces put this object over the original base, make it non-renderable (object settings > renderable off)
Marcin Miodek | chaos-corona.com
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2015-09-30, 16:19:17
Reply #4

Torsten

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Super! Thanks to your tip it worked, i got myself a path.

2015-09-30, 17:18:25
Reply #5

maru

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Great, you can also paint some details on the path so that:
a) the grass is not "cut off" but gradually becomes less dense - you can blur the edges of path for this, or feed vertex color map into color correction node and change gamma/pivot/gain
b) use the same/modified map as scale map, so that there are bigger and smaller grass clumps
Marcin Miodek | chaos-corona.com
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2015-09-30, 17:37:52
Reply #6

Torsten

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Thanks for the tips!

unfortenately my grass patches are circles of 1 meter diameter. I think that is the reason the edges do not look that good. Don't know if blurring the edge of the vertex color helps for making the edge the way it looks now.

I am not too satisfied with how the edge looks at the moment. Maybe i need to put smaller grass clumps manually at the edge?

2015-09-30, 19:31:59
Reply #7

romullus

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You can create second scatter for smaller grass patches and then tweak density map's curves of that scatter.

Attaching max2011 scene for example.
I'm not Corona Team member. Everything i say, is my personal opinion only.
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2015-09-30, 19:58:43
Reply #8

Torsten

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Cool! I didn't know that technique, i will give it at try for the next test render.

Thanks!

2015-10-01, 11:00:37
Reply #9

rambambulli

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I was wondering, why not only use the small patches?
I have done some tests with Forest Pack and with Corona Scatter and I can't find a real difference in render times when using only small patches.

Small patches adopt better to terrain nuances work better with edges, color variation, and clustering of variations.

Am I overlooking something here?


2015-10-01, 11:56:51
Reply #10

romullus

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Well, one still can use small patches for main area and individual blades for edges :] I'm glad to hear that there's no significant differences between huge and humongous counts of instances.
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2015-10-01, 12:16:03
Reply #11

maru

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Some time ago Ludvik explained to me that it is best to use as few instances as possible - so the most efficient would be to create big grass clumps. I am not sure how important it is, though, but I guess this should not make much difference unless you are scattering billions of high poly objects. So:

one high poly grass blade per proxy:
-small field = ok
-huge area = no no

lots of high poly grass blades per proxy = ok, unless it is impossible to use (for example edges like mentioned above)

lots of low poly blades per proxy = best (obiously); if possible, as above
Marcin Miodek | chaos-corona.com
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2015-10-01, 13:39:37
Reply #12

Torsten

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So using the output maps on the Vertexcolor seems to do a good job. This is how the path looks like now. I have used large patches of grass for the main surface scatter, and used smaller patches (10% of the large patch) for the border/edges. This does a pretty good job.

The only problem i am having is the control over the width of the border. I can't seem to make it wider. I attached an image of romulus file where i put arrows for direction. I want to have control of how far from the border the objects are scattered. And it would also be nice if the scatter would be less dense further from the border. ( i painted how i think such a distribution would look like in graph).

2015-10-01, 14:08:38
Reply #13

romullus

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Small patches won't extend in areas where vertx colours are pure white. You have to add more information into vertex map, either by bluring existing vertex colours or adding grey colours manually with a brush.
I'm not Corona Team member. Everything i say, is my personal opinion only.
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2015-10-01, 14:23:47
Reply #14

Ondra

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Some time ago Ludvik explained to me that it is best to use as few instances as possible - so the most efficient would be to create big grass clumps. I am not sure how important it is, though, but I guess this should not make much difference unless you are scattering billions of high poly objects. So:

If you can afford to choose (which usually is not the case), when instancing/scattering, it is always best to minimize the higher of (number of instances, number of polygons in the instance). This is usually done by having approximately same number of instances as number of polygons. This will be the best compromise between speed and memory usage.
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