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All About GlowDomes (tutorial) by Howard Prince« Previous Image Last page in History Next Image »
Artist's Comments: !div style="display:none"!edf40wrjww2gallery:imagedesc!/div!Global illumination via HDRI images can be learned from the following link:

http://graphics.stanford.edu/~henrik/images/global.html

Prior to CX, released in May/2004, Strata didn't support HDRI images;- these are specially prepared images with multiple overlays of contrasting colors in order to create a truly dynamic lighting scheme. When mapped to an entire environmental object (something that surrounds the whole 3D scene), the lighting is as close to "realistic" as you can get because of the diffused lighting effect that comes from all the different directions that the image can generate.

While Strata doesn't currently do HDRI, it can quite successfully eminate the effects of HDRI Global Illumination by using the clever and unique "GlowDome"; the above images were all done with it.

There have been many inquiries about using the Glowdome technique in the StrataCafe forums... so, while I'm no expert, I have done quite a bit of research and experimenting into this area (as it is my main form of lighting in my work), and am happy to share what I know.

The following is "GlowDomes", as told by yours truly:

In order to create a truly realistic environmental lighting scheme, one must be able to understand that just one source of light cannot correctly replicate the real world, where, even with one primary light source (such as the sun), much of the "realisitic lighting" throughout results from the diffussion of that light (and others, as well) as it bounces off of one object after another throughout the scene, fading its' intensity with each bounce, until, finally, there is nothing left of the original light ray, except a trail of objects it has affected all around the scene.

In Strata, the way to achieve that desired diffused light effect is to use a "GlowDome" and render the scene with Raydiosity; this will allow the correct reading of diffused light from the "glow" texture and follow its' path around the scene. The settings should be tweaked a bit higher from the default "Raydioisty Best" according to your image needs, but remember, tracing all of those light rays bouncing all over your scene is a time consuming task, so "tweak" upward in moderate steps, and experiment.

Ok... now for the "meat":

1. Prepare your scene... put your models in place, make a separate camera view of the rendering you want to execute, leaving the model window free to work in, and when you are done with all that, you are ready to make your GlowDome.

2. There is nothing tricky about making a GlowDome. Just make a perfectly round sphere, place it at 0,0,0, and then enlarge it to surround your scene.

3. How big? Well, I use a ratio of 60:1; that's a 60" diameter for every 1" of scale. If you are working in feet, then you'd start with 60'- just make sure that your sphere totally encompasses your scene.

4. Next, you have to make a new Surface Texture. This is where the "Glow" in the GlowDome will come from. Almost every channel should be set to "0" except for the Diffuse Color, Diffuse Map, Ambiant, Opacity and Glow.

To begin with, you have to ask yourself what type of lighting you want your scene to have. Dark and mysterious, or bright and sunny? Choose an image that has those characteristics, and bring it into the Diffuse Color channel. If you are going to see the image in the background because of the camera position, then you may want to use Photoshop or some other image editor to convert it to polar coordinates first, so that it maps correctly to the sphere, and won't appear distorted, but, if you are just looking for great, realistic lighting with nice contrasting reflections and will NOT see it in the background, then that additional task isn't necessary.

5. Apply that same image to the Diffuse Map channel, and the Glow Channel.

6. Set the Glow to "1", Diffuse, DIffuse Map, Ambiant and Opacity to "100%", then name your texture "GlowMap" and apply it to the sphere you made, using projection mapping (you ca
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