Render Challenge
Volumetric Lighting

A Quick 'n' Dirty Tutorial for Faking Volumetric Shadows

For those people who need a quick and easy way to snap up that flying logo, I present to you fake volumetric shadows. The first thing to recognize is that Inspire 3D does not do true volumetrics. The Inspire 3D tutorials walk you through faking volumetric lights using the Fractal texture -- if anyone had any specific problems with the tutorial, feel free to e-mail me at "" and let me know what results you got and I'll try to troubleshoot the problem -- the tutorial was fairly quick and easy itself, so I thought I'd do volumetric shadows instead. The methods used were "inspired" by Alan Chan's article in Lightwave Pro Magazine; it also appears in The Lightwave 3D Book. If you get a chance, check it out in your local computer bookstore; it's full of very useful tips and pro secrets, and because most of it was written for earlier versions of Lightwave, most of the book relates quite nicely to Inspire 3D.

Because you can't get true volumetric shadows out of Inspire 3D you have to build the shadows as a second object. Here we go...

To build the picture above, first type in the word(s) you wish to use (Mac users, if you don't see the option to add TrueType fonts, it's because it's missing, so don't panic -- use PostScript fonts, or build a font outline in Illustrator or Freehand and import it as an eps). Before extruding the logo, select-copy-paste the points/polys onto a second layer.

In the first layer, extrude the words or logo the amount you think looks nice (see below). I've picked the font "Stop" below, and extruded slightly. Once extruded, I selected all the poly's, gave them a surface name (in this case, "Inspire") and [Put] them into Layout.



Once that was done, I went to the second layer, selected the poly's and extruded them approximately 20 times the length of the letters' extrusion (see below). Once extruded, I selected the front and back poly's and cut them, making each letter into a hollow extrusion.

Once the end caps were deleted, I selected all the poly's and used the "flip" command to turn all the poly's inward; the next step was to select all the remaining poly's and apply a surface to them (I used "InspireShadow"). The surface color I used in the sample above was 10, 10, 20, and the only thing to remember at this point is to uncheck "Double-Sided." Once that is done, the only polygons visible to the camera are those furthest away from it.


Switching to Layout, the first thing I do (after saving the scene) is to parent the shadow to the letters -- this will allow you to move the letters around, resize them, etc., and not worry about lining up the shadows to the letters.

Once that's done, I added two lights directly behind and slightly below our letters. For the shot at the top of the page, I placed the camera below the level of the letters (as seen below in the side view).


Now comes the fun part (to me, anyway). First, I textured the letters; I chose "Gold" -- here's where a minor annoyance pops up. Once "Gold" is selected, Inspire informs you that it can't find "FractalReflections.iff" at which point you point it at "FractalReflections.tga" (in the Images/Reflections folder). It's a minor annoyance, but one which is easily dealt with (for most people).

Next is the shadow's texture. The numbers are:

Surface Color: 9, 10, 20
Luminosity: 100%
Diffuse Level: 0%
Transparency: 0%

Transparency Texture

    Texture Type: Grid
    Texture Fallof: 0, 0, 10.0
    Texture Value: 75%
    Line Thickness: 1.0
    Edge Transparency: Transparent

For the two lights, I used lens flares, calling one MainFlare and the other GlowFlare. As mentioned above, they are in the same position, behind and slightly below the letters. Their settings are:

Flare Intensity: 200%
Flare Dissolve: 70%
Central Glow: On
Red Outer Glow: Off
Glow Behind Objects: On (Note: I get a warning here that it's not for flares, but it seems to work anyway).
Central Ring: Off
Random Streaks: Off
Anamorphic Distort: On

Flare Intensity: 300%
Flare Dissolve: 0%
Central Glow: On
Red Outer Glow: Off
Glow Behind Objects: On
Central Ring: Off
Random Streaks: Off
Anamorphic Distort: On

And that's basically it. The results of the above settings gives you the picture above. It's by no means perfect, and by experimenting with the different texture and light settings, you can have a lot of fun and get some pretty wild results.

For animations, because the shadow object is one-sided pointing inwards, if you move the camera in a semi-circle arc in front of the letters, the "shadows" will react properly, always looking as if they're being cast by the letters. You can have some fun as well by setting a velocity to letters' texture while animating, giving it different effects with variable settings.

Besides letters and logos, you can use the effect for setting volumetric shadows of characters or vehicles; Mr. Chan gives a beautiful example of a ship moving away from a planet that has a huge sun behind it. The effect is handled roughly the same way -- select the points on the outline of the object, polygonize them, then extrude them. The points you choose define the "shape" of the shadows.

An even quicker way to do this using Inspire is with its Sketch tool. Import the object or figure you wish to shadow, and instead of selecting the points, go to another level (using the imported object as a template) and use the Sketch tool to trace a rough outline of the object -- it doesn't have to be exact, it's just a shadow (see below).



Polygonizing and extruding the shadows works the same as with the "Inspire 3D" example above. In this case, below, I've used a character-in-progress (I still have a lot of clean-up, and there's no texture maps applied yet) to demonstrate a colored, more subtle shadow effect.


That's it. If you have any problems or questions, feel free to email me at "" and I'll try to get back to you as quickly as possible. In the event of a problem, please describe exactly where you're having the problem, or what results you're having.


Walt Sterdan


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