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    In this little tutorial we're going to see how to create an awesome scanning electron microscope shader. All tutorials I saw about this, used bad method but the basics are fine. If we see a true scanning electron microscope image (sem), here, we can see that all stuff receive and casts shadow. An Scanning Electron Microscope works equal than our radiosity engines: shoots some electrons to the object and this electron bounces several times, lighting all the tissue or whatever we want to see.

    The problem with shaders shown in tutorials (like red blood cell, in Newtek's site) is that our object cannot receive any shadow (shot), or can receive if setup diffuse to 100% but it's unuseful because our object will be a light emitter (remember the gradients in luminosity...), and we don't want this. But this have an easy solution. We'll apply the gradients, controled by light incidence angle, in diffuse instead of luminosity. Because at 100% there's no difference with normal object, we're going to set maximun to 200% or more, and minimun to 50% or little less. Be careful, shaded area do not have to be 100% dark (as you can see in real SEM image, there is not "super black" areas). You must have something like this in diffuse, *not in luminosity*. For color, you can copy/paste the diffuse parameter to color, and modify them if you want. Add some bump. We have all shading ready, now we have to activate radiosity to render the scene as a scanning electron microscope does: we shoot rays to our scene, which will bounce several times lighting our "tissue" :). You can see here an example.

    We can modify the colour, bump, diffuse to obtain several types of SEM shaders for different objects in a "tissue".

Warning: Don't try this at home.

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