The BRAWL² Tournament Challenge has been announced!
It starts May 12, and ends Sept 12. Let's see what you got!
https://polycount.com/discussion/237047/the-brawl²-tournament
It starts May 12, and ends Sept 12. Let's see what you got!
https://polycount.com/discussion/237047/the-brawl²-tournament
Shader
polycounter lvl 17
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Replies
pass 1 - normal alpha blend
pass 2 - invert the alpha channel and multiply by color, this should leave you with a soft edge from the texture, apply this additivly
blend: a*t + (1-a)*f
add: t + f
where t=texture, f=on screen fragment/backbuffer, a = alpha of texture
If you take a premultiplied alpha texture with t'=t*a and use the standard blend mode, then you got:
blend: t' + (1-a)*f = t*a + (1-a)*f
You can now use the alpha value to increase the influence of the fragment by setting a=0
t'+(1-a)*f = t'+(1-0)*f = t'+f = additive mode
So, it is just a matter of the texture if using the standard blend function 1*t'+(1-a)*f
The trick is , to use separate alpha values for the premultiplied part of the texture and the alpha channel:
a = alpha value for premultiplication
b = beta value for shifting between standard blend (1) and additive mode (0)
The texture should be constructed like this.
t_base = base_texture = (color_base,alpha_base)
beta = 0..1
t_new = (color_base * alpha_base, alpha_base*beta)
A standard premulitplied texture would look like
t_premulti = (color_base * alpha_base, alpha_base)
Setting the beta value to 0 will result in pure additve mode.