* Subject: Soft Shadows RE: Is it Possible? * Date: Wed, 1 Jun 94 13:52:25 EDT [51] * From: jgoldman@acs.bu.edu (Jeffrey Goldman)1. Figure out how many lightsources you will have in the final packed bundle. In this case it will be 21 (not exactly arbitrary and you'll see why).
2. Figure out the final intensity of the packed bundle. In this case it will be 255, 255, 255 (the default value for an Imagine lightsource). The packed bundle (with all its lightsources) must emit as much light as a similar single lightsource otherwise you get too hot a lightsource.
3. Divide the final intensity by the number of lightsources (step #2 divided by step #1). This gives the individual intensity for any lightsource that makes up the packed bundle. In this case 255/21=~12.1.
4. Add a primitive disk with radius of 100 and 10 sections.
5. Add an axis and place it at the center of disk. If you're using defualts the axis will autmagically appear at the center of the disk (world center of 0,0,0)
6. Select the axis you just added and enter the Attributes requester.
7. Make the axis a Lightsource with Light Intensity settings of the number you got in step #3. In this case it's 12.1, 12.1, 12.1. Have the axis Cast Shadows. If you're using 3.0 and like Lens Flare disable the feature for now.
8. This bundled source will act the same as point source. With that in mind determine whether the light should fall off. For these purposes have no light fall-off. Exit the Atributes requestor.
9. Copy the axis (R-Amiga C), paste it (R-Amiga P), and move it (m) to the top of the disk where the the edge of the disk and the section parts meet.
10. Copy and paste the axis at every section around the outer rim of the disk. This will result in 10 axes at every section and one axis in the center. Delete the disk to get it out of your way.
11. Group the outer axes to the center axis by selecting first the center axis then every outer axis (using shift), and finally grouping the with (R-Amiga G).
12. Copy this entire array of 11 lightsources and paste it.
13. Select one array and scale it by .5. This should bring the outer axes closer to the center.
14. Rotate the same array by 18 degrees. This causes a stagger of the inner array as compared to the outer array.
15. Enter Pick Objects Mode and delete the center axis out of one of the arrays (you only want one center axis). Group the non-grouped axes to the center so that every axis is grouped to the center axis.
16. Enter Pick Groups Mode and save the entire bundle.
A word for Imagine3.0 users. If you want Lens Flare to operate for this bundle select the center axis and enable the flare. Having all 21 axes Flare would be tediously slow, and it wouldn't look good.
=== Using the Bundle in the Stage Editor ===A warning. This bundle object is made of 21 lightsources. Rendering times will decrease with its use for obvious reasons.
The bundle only works in Trace Mode (obviously) because it needs to cast shadows.
The current bundle only works in "Studio Situations" or situations where the bundle only has to work in a near perpendicular fashion. I.E. The pyramid of spheres on a flat plane would be a studio situation. You can aim a lightsource as if you were in a studio or soundstage.
The bundle must always be perpendicular or near perpendicular to the subject. You can track the Y-Axis to the subject to achieve this.
Each of the axes on the bundle emmits a bit of light. It's the multiple shadows cast by each of these lights that creates the soft shadow. You must be prepared to experiment with the scale of the bundle. Scales should always be done (L)ocally. It's pretty easy to figure out how large the bundle should be if you understand how the bundle works. This I leave up to you as it is next to impossible to explain the 'right' scale setting...
Always remember that the more lightsources you use in your bundle the better the results, and sadly the longer the rendering times. You have to make a trade off between how large your soft-shadow fall-off will be compared to how many lightsources you have in your bundle. If your soft-shadow area is too large, and you don't have enough lightsources, you'll see many clearly defined sharp shadows.
This the only way to created a soft-shadow lightsource in Imagine, I believe. It may be a pain in a$$ but it works. It should only be used for stills for obvious reasons. Only use the bundle where necessary. For instance, in a conventional three point lighting setup you only really need the bundle for the Key and Back lights. The Fill doesn't cast too noticable shadows and can therefore be a point source.
Oh, one other thing. Specular hits look way cool with light bundles. I mean much more realistic...
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