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Author Topic: Density Falloff Issue  (Read 4937 times)

Mike Truly

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Density Falloff Issue
« on: November 07, 2009, 02:37:03 PM »
Carlos,

I love the Density Falloff settings in the Area panel.  But there are some issues I have with it.  See the attached image.  I may be using it incorrectly for what I want to achieve.

I have a view from a camera and the camera moves (slightly) throughout the animation.  I want the trees (actually grass in this case) to falloff away from the camera view.  I create a circle spline and position the center of the circle at the location of the camera and have the Density Falloff falloff away from the camera towards the horizon.  This all works fine.  But I don't need an entire circle filled with grass so I must use Exclude Splines to NOT create grass in most areas.  But I need LOTs of grass within the grass area.  This method seems to be limiting how much grass I can create because the entire circle must be created with grass.  This is crashing MAX when I try to increase the grass amount.

Ideally, I want to create only the desired shape Include Spline and then define the falloff using a simple line... falloff in the direction from pointA to pointB.

I need even falloff so I use a circle from it's center to it's edge.  But maybe I am misunderstanding how Density falloff works.  How can I make the falloff even when the Include spline shape is irregular?

Thanks!


Sincerely,

Mike Truly
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iToo

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Re: Density Falloff Issue
« Reply #1 on: November 07, 2009, 04:21:39 PM »
Hi Mike,

Quote
I want the trees (actually grass in this case) to falloff away from the camera view.

Why don't you use density falloff from Camera rollout ? It does exactly what you need, decreasing the density away the camera position.

Quote
This is crashing MAX when I try to increase the grass amount.

Are you using VRay ? There is a bug in 3.2.4 that crashes Max when 'Max trees' (Display rollout) value is reached, instead displaying the 'F' icon that is the correct behaviour. This problem is fixed in recent betas, for previous versions try increasing 'max trees' parameter.

Carlos Quintero
iToo Software

Mike Truly

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Re: Density Falloff Issue
« Reply #2 on: November 10, 2009, 03:47:11 PM »
Carlos,

Sorry it's taken so long to get back to this.

I am not using Camera Density Falloff because the camera moves during the animation (and it tells me not to use this in the dialog for this reason).  The Area Density Falloff is great, but as mentioned before, I have to over-create many trees (that I don't need) just to get the area and density falloff I DO need.  In my case, it would be much better to be able to create an irregular Include spline and define the linear falloff direction with a 'Start/End' line that I define... something for the wishlist.

I have V-Ray but am not using it for this project... I am using Scanline.  I did get the 'F' icon so I will try upping that setting.

Thanks!
Sincerely,

Mike Truly
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iToo

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Re: Density Falloff Issue
« Reply #3 on: November 10, 2009, 04:50:49 PM »

Hi Mike,

We suggest to don't use Camera Density Fallof with animations because the distribution changes when camera moves, and in most of scenes this effect is not desirable. But, to create grass and using a far range value you can use it without problems (in fact, i think that we are going to remove this warning from the plugin).

Quote
I have V-Ray but am not using it for this project... I am using Scanline.  I did get the 'F' icon so I will try upping that setting.

Well, using scanline is not strange that max crashes with dense distributions, since it tries to creates a huge mesh for all the plants.

Carlos Quintero
iToo Software

Mike Truly

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Re: Density Falloff Issue
« Reply #4 on: November 18, 2009, 06:31:25 PM »
Carlos,

I finally got back around to this.

I tried using the Camera Density Falloff but the results are not desirable with the grass popping on and off while the camera moves (the Density Falloff is being adjusted as the camera position is being adjusted).  Maybe it works with a stationary camera that only pans but not with a camera that dollys forward.

So the Area Density Falloff is the way to go.  But again... it would be nice to not have to create a giant circle spline (and the massive amount of grass with it) just to get the falloff to falloff from the viewpoint location to the horizon, then use Exclude splines to trim to an irregular shape.

For me, it would be far better to draw just an irregular shape (Include Spline) and then define the falloff direction (somehow... with a two point line).  In essence, this is what Camera Density Falloff tries to do (and it works great... until the camera moves).

Maybe I'm using the Area Density Falloff incorrectly for what I want to do.  The previous attached image shows the irregular area that I want to have grass in.  But I want the grass to falloff from the camera location (and the camera does simply move in a straight line from the start position forward to the stop position).  The density falloff of the grass needs to remain fixed as the camera moves.

Thanks again.
Sincerely,

Mike Truly
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yuv

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Re: Density Falloff Issue
« Reply #5 on: November 18, 2009, 10:10:19 PM »
Hi Mike,

One possible solution to get a Falloff effect with fine control indendient of the camera, is to use a gradient texmap as distribution. In the atached example i used a circular gradient with a little of noise as distribution map, later i can control the shape of the area using inclusion lines. The camera can freely move while the grass is fixed and items don't pop.

Using differents gradients or a custom bitmap you can control were exactly you want to have the Falloff.

Please, make sure to use the latest beta to open the scene.
Daniel Quintero
Itoo Software
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daniel@itoosoft.com

Mike Truly

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Re: Density Falloff Issue
« Reply #6 on: November 19, 2009, 12:00:20 AM »
Thanks very much for this Daniel!  I'll give that a try.

Thanks again.
Sincerely,

Mike Truly
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CQ1841

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Re: Density Falloff Issue
« Reply #7 on: December 10, 2009, 07:35:25 AM »
It's a good idea to use camera clipping/falloff and to ensure you use it to scale down the items before altering their density, so that, in the distance, they scale out of existence, so that any pop is unoticeable (because they're at 0 scale).

Mike Truly

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Re: Density Falloff Issue
« Reply #8 on: December 14, 2009, 02:22:35 PM »
Sorry it's taken awhile to get back to this.

Thanks for the ideas.  I'm not sure what you mean about scaling.  I understand the concept of scaling trees down to nothing off in the distance, but I see no setting in the Camera section for scaling trees.  I see a 'Density Falloff'  but not a 'Scaling Falloff'.

Thanks again.
Sincerely,

Mike Truly
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