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oordeel

simple special effects

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Hi Guys, I was wondering if you had any tips or info in order to do some simple special effects, not using shaders. I was thinking along the lines of putting a bounding sphere around models and then maybe animate them ? Or should I just stick to particles for the effects? Also, how would I go about creating an aura of sorts? Any hints and tips are appreciated. Thanks,

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If you'd like to render an aura, like a magic Halo for eg, you'll might want to read "Improving Shadows and Reflections via the Stencil Buffer" by Mark J. Kilgard (nVidia Corporation)!

A little snippet from the PDF file:
"Magic haloes. A magic halo extends a glow around an object, but the halo does not
obscure the object itself (that’s what makes it a “magic” halo).21 A game may use a halo to
indicate that a particular character or object has a special capability or power.
The halo effect can be accomplished by first rendering the object with a particular stencil
value. Then apply a scale transformation centered at the object’s center to the modelview
transform. Render the object’s geometry a second time (scaled larger this time) but color
the object based on the intended glow color (instead of the object’s normal color and
texture), and use stenciling to not update pixels tagged with the particular stencil value
used to render the object the first time. This way the halo does not obscure the object.
Finally, undo the scale transformation. Optionally, use blending to blend the halo with the
background behind the object (use stenciling to avoid double blending as necessary). This
works best when the object is relatively convex. However, in the case of a non-convex
object, break the object into convex pieces and extend the halo around each piece. Figure
17 shows an example of such a stenciled magic halo applied to a sphere.
I’ve recently seen a Quake 2 mod that tries to accomplish the basic idea of a magic halo
around certain characters, but without stencil. The scaling approach described above is
attempted, but without the benefit of stencil. Not only is there unsightly double blending of
the halo, but the yellow halo covers and obscures the entire character (instead of just being
a glow around the character). The effect is something akin to seeing a guy walking around
covered in yellow radioactive snot. Stencil could make this look much cooler." Mark J. Kilgard.

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thanks for the tips guys. Any more tips or suggestions as to some special effects and how they're accomplished would be great.
I'm gonna play around with this tonight and how it turns out.

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Correct me if I'm wrong, but couldn't you just scale up and recolor the object, render it, then disable z-enabled, reset the object, render it over the aura then re-enable the z-enabled. That way you don't have to mess with stencils.

Just my way of working around what I don't know [wink].

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