Tutorial 1: Volumetric Fog in Inspire 3D


Ok, so you can't use steamer in I3D. So what? Here is a techniques that will not only simulate the effect, but make the Lightwavers jealous of it's rendering speed. ;-)

Step 1: Go into modeler and from the top viewport make a 30 meter square.

Step 2: Hit Control-c to bring up the Clone requester. Enter the following values:

And hit OK. What we just did is made eight copies of this polygon and raised each of them 75 mm .

Step 3: Now from the front view, select the bottom-most polygon (you'll have to zoom in a little). Hit "q" to bring up the surface panel. Name it "GroundFog 1" and hit Apply. Now, select the next higher polygon, go into the surface panel and give this one a surface name of "GroundFog2." Repeat this procedure for the other 7 polygons.

Step 4: After you're done surfacing, unselect all polygons and hit "f' to flip the polygons so they are facing upwards. Save the object as "GroundFog.lwo" or something similar. Now head on over to layout. This is where the real fun begins!

Step 5: First, let's set up a basic scene with a camera and a light. Select the Camera editing mode and punch in the following:

Don't forget to keyframe it!

Now select the Lights editing mode and rotate the light to:

Keyframe this too. We don't need to worry about the position of the light because it is a Distant Light, only direction matters.

Step 6: Load in the GroundFog object and go into the surface panel.Select the "GroundFog 1" surface. Now set the following settings:

You may pick any color you wish. Hit the Texture button for Luminosity and pick Fractal Noise for the type. Enter these values:

Now adjust the Size and Falloff values as follows:

Render a preview sample. If you size the sample to 10 and make it a cube, you can see how the texture fades to nothing in 10 meters. Select the "GroundFog 2" surface and click on the sample preview you just created. Click "yes" on the panel that comes up to copy the surface setting from "GroundFog 1." The only change you need to make is to raise the Transparency 10%. Now click on each successive surface (GroundFog 3, 4, 5, etc.) and raise each of their transparencies 10% higher than the one before. You should end up with "GroundFog 9" with 80% transparency. That's it, we're done with the surfacing. Pretty simple, huh?

Step 7: Go into the Camera panel and activate the following settings:

You may raise the AA higher, but Low will suffice for our example. In the Lights Panel, lower the Ambient Intensity to 5%. Before you press F9, I would recommend that you load an object (a simple disk or cone will do) that goes all the way through the fog object (i.e. it goes lower than 0 m and higher than 0.6 m). This will enable you to visualize what is happening in the following steps.

Step 8: Now press F9 to render a frame. In a few moments, you should see:

Cool fog, but what's up with the lines?!? Well, what we have done so far is built polygons with fading layers of transparency and the bottom polygon being solid to create a volumetric effect, add depth to the fog, not let us see through the fog, and be the place from where our fog texture starts from. As you can see, these polygons create "hard" edges when they meet with an object. We need to solve this problem.

Step 9: We are going to use a common rendering effect called Motion Blur. This blur is based on how fast the object is moving and the Blur Length set in the Camera Panel. Select the GroundFog object and hit "m"to bring up its motion graph. For the channel, pick Y Position. Change the Current Value to -0.075 (-75 mm). Create a key at frame 1 and give it a value of 0 and change the End Behavior to Repeat. Your graph should look like this:

What we have done here is started the object at 75 mm below ground level and at frame 1, the object moves to ground level. What this does is at frame 1, it moves each polygon to the the position of the one above it and blurs its path to create a smooth transition and therefore gets rid of those horrid lines we saw earlier.

Step 10: This time, instead of using F9 (which renders frame 0),we will use F10. This renders the first frame of the scene and if you look in the Render panel, the "real" first frame is set to 1. This also allows our blurring to take place between frame 0 and 1. So hit F10 and you should see:

Not bad. But you can still see traces of the lines we had seen earlier.

Step 11: To fix this, go back to the Graph Editor and lower the value of the key at frame 0 from -.075 (-75 mm) to -.15 (-150 mm). Now, each polygon gets raised to the second one above it and the blur effectively cancels out the lines that we saw earlier. How does it exactly "cancel" out the lines? Well, since the polygons are moving to the second polygon above them, they pass the "line" where the polygon immediately above them stood and since they are blurred, the blurring covers that line and this happens throughout the object canceling every polygon from top to bottom (except the lowest one, which is good because that defines the"ground" and should not be blurred as much). Confused? Good, so am I. :-)

One thing to keep in mind is the more you blur the object, the more the textures get blurred and subsequently lose their detail. To some extent this is a good thing because it helps in the overall "volumetric" look that we were shooting for. If you compare the past 3 test renders, you can see this in effect.

Step 12: That's it! This techniques may as well be applied to other situations. So experiment and have fun in the process!

Here are some examples with different settings:

1. Small Power changed from 0.5 to 1:

2. Small Power and Contrast changed from 0.5 to 1:

3. Try adding the SurfBlur filter to the 9 surfaces. This gives it a soft look, adding to the volumetric effect:

As always, comments, complaints, suggestions, send them all!

-Mostafa Sadraii


If you need to contact me, please use: mosadraii1@hotmail.com