Hi all
Is there any way to make glow effects in GLB?
What I'd normally do is use an alpha channel and additive blending. I don't think GLB can currently load graphics with alpha channels?
I've tried alphamode 0.1 -> 1.0 with a variety of graphics but I'm not able to find anything that works for me.
I also found this (http://www.retroremakes.com/forum2/showthread.php?t=9189&highlight=Glow+effect) (scroll down to Gernot's post) which looks interesting over at RR, but I can't seem to get it to work.
Any suggestions (and code examples)?
You can load alpha channel PNGs. No Problem.
My vector scramble and the Quantum remake have "glowing" lines. Is that what you need?
Ah - cool. I think I must have messed up my alpha channel when I saved my image and just assumed they weren't supported. This is perfect then thanks. I remember a post now that I think about it, it's only OpenGL platforms that support the alpha channel so PPC and GP2X will ignore them, is that right?
Yes, I came across that line effect in that linked post which looked cool in the screenshots but I couldn't figure out how to use it as my line didn't look the same. I'd like to put a small glowing trail on some objects.
PPC will ignore it. I'll have to fix that one now. Darn.
Do you want a polyline or a single line shaded?
I'm making a quick game (for the RR project) for Windows, Mac & Linux, so I don't need the alpha channel support for PPC right now. A nice to have for the future when you've some time to look at it I guess.
I'd like to make a short to medium length trail for an object that doesn't change direction. The line will be around 8 pixels width, but could be wider, and I'd like it to fade out at one end.
Got the glow effect I am after (thanks to getting the alpha channel working right along with the additive alphamode) and I've modified the CoolLine function to draw a glow line in the way that I want (code below). Thanks for all the help on this :)
// to make this more flexible, could work out the sprite (spr) image width and height - I've got it set up for a 32x32 sprite.
FUNCTION CoolLine: spr, x1, y1, x2, y2, w, col, alpha
LOCAL c,s,p, dx, dy, ddx, ddy, ux, uy, lg
// direction of line
ddx = x2-x1
ddy = y2-y1
lg = QSQR(ddx*ddx+ddy*ddy)
IF lg<0.1 THEN RETURN
// short caps
lg=lg+lg
// dir vector
dx=ddx*w/lg
dy=ddy*w/lg
// up vector
ux=dy
uy=-dx
ALPHAMODE alpha/2
STARTPOLY spr
POLYVECTOR x1+ux*2, y1+uy*2, 0.5, 0.5,col
POLYVECTOR x1-ux*2, y1-uy*2, 0.5, 31.5,col
POLYVECTOR x2-ux*2, y2-uy*2, 31.5, 31.5,col
POLYVECTOR x2+ux*2, y2+uy*2, 31.5, 0.5,col
ENDPOLY
ALPHAMODE alpha
// center
STARTPOLY spr
POLYVECTOR x1+ux, y1+uy, 0.5, 0.5,col
POLYVECTOR x1-ux, y1-uy, 0.5, 31.5,col
POLYVECTOR x2-ux, y2-uy, 31.5, 31.5,col
POLYVECTOR x2+ux, y2+uy, 31.5, 0.5,col
ENDPOLY
ALPHAMODE alpha/2
ENDFUNCTIONHere's the image I'm using....
(http://baa.ovine.net/texLaser.png)
Ah. The image I was using was a circle rather than a bar-shaped image. Then the caps are drawn "rounded". But you removed the caps, too. So, no worries.
Yes, I need to put the caps in again now (as I'm using connecting lines). I realised that is what your example should have been doing but I was having some problems with it (it wasn't putting rounded edges on). It might have been a bug in my code though, as I fixed something in my sprite handler. I'll post an update to the code I'm using tonight.