Quote:Original post by ehmdjii
i am trying to implement the effect of an object, which, when moving around, leaves a glowing trail behind.

I implemented a ribbon-trail effect a while back, for Ashima IV:

Quote:i was wondering how this effect is usually done. are the polygons of the trail procedurally created? do you usually use quad strips? or triangle stripts?

Basically, I regenerate a quad strip programmatically on the CPU each frame, from a queue of recent positions, and use a vertex shader to make each quad face the camera.

Quote:what about the texture coordinates? and how does the texture itself look like?

I passed in texture coordinates only for the x dimension (i.e. across the trail), and used a 1-dimensional texture (expanded for clarity):

Quote:ideally the trail fades out at the end.

I passed the normalised length along the trail with each vertex, and used that to modulate both the colour and width, causing the trail to fade out in the distance.

Quote:what about the blendmode to use to make it glow?

I used additive blending. Other blend modes are possible, but additive blending avoids having to sort the quad sections by distance, and avoids issues where a trail loops around on itself.