The floor fog on this pic

I made with a cube an ScatterVolume

My question is, is it possible to make the VolumeSactter like a gradient with more at the bottom and less at the top of the Cube.

I don't realy understand how the xyz coordinates effects the volume.. I tired out many combinations, but I don't realy find out a logic.

]]>The floor fog on this pic

I made with a cube an ScatterVolume

My question is, is it possible to make the VolumeSactter like a gradient with more at the bottom and less at the top of the Cube.

I don't realy understand how the xyz coordinates effects the volume.. I tired out many combinations, but I don't realy find out a logic.

]]>Amanda

]]>V node is on the surface, not interior.

I generally modulate fog with the P node, which gives absolute position in the scene.

If you set the x and z parameters to 0, then the P node reads out height.

The units of the P node are 1/10 of a Poser inch, so to read out a value as inches, you would set the y parameter to .1.

Since the P node is officially a vector, when you plug that into a number channel it will be converted to a number by averaging, i.e. (x + y + z) / 3. Since we would actually want the inches to come out, you should triple the y parameter, so that the calculation becomes

Y = (0 x + .3 y + 0 z) / 3 = .1 y

Once you have height from the P node you can do lots of math with it, including decide on a blended density from A to B as in

factor = (Y - A) / B

Use that factor to control whatever you want, most directly into Mix or Blender nodes. If you're going to use it in other math nodes, you'll want to clamp it first.

Instead of the legacy P node, you could probably also use the Cycles Geometry node, which has a Position output, but I'm not sure if that is operative in a volume shader. Certainly the Normal output is probably inactive in a volume.

]]>I was not sure if I understand exatly what you mean, but my test render brings exactly what I was looking for :-)

]]>I have no privilegs to upload files here, but try to download it here

https://drive.google.com/file/d/0B7EIm43DOjsAM0IyUTRQZFh1Z2s/view?usp=sharing

Rendersettings

Even with your scene at first i could not get the same result as you. It was have because of my settings where in poser native units.

I had to change to inches, close the scene and reopen it to get your results.

First fail due to units :

after inches... Thats it !

I think i will keep to inches.

Using

I get

and reducing the Y scale, and increasing the X and Z scales on the cube I get

]]>Here is the Poser box, with the surface lit by the V node.

Here is the volume lit by the V node.

Interesting. I would have checked on this yesterday but I didn't have the time. So it would appear that in a surface shader, the V node gives you the V value from the UV mapping, but in a volume shader it can't do that. I expected it would give nothing, but instead it gave something proportional to P.y.

Guessing that U node would give something proportional to P.x, it seems to do that.

]]>Anyway - here's a setup involving the modulation of the clouds, so that at the bottom it's solid fog, and then it breaks up from 10 to 40 inches. Above 40 there is nothing.

]]>I save your explanations. I'm sure I'll can use this very well :-)

]]>Amanda

]]>