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[Jesse]

I've writing a small application for both Windows/GL and the PSP, but there is one blending-mode that doens't seem to work the way I intend it.

[fish]

[Jesse]

I don't think there is such thing as GU_MUL.

GU_ADD, GU_SUBTRACT, GU_REVERSE_SUBTRACT, GU_MIN, GU_MAX and GU_ABS are the ones defined.

[sebbbi]

sceGuBlendFunc(GU_ADD, GU_DST_COLOR, GU_ZERO, 0, 0);
= (src_color * dst_color) + (dst_color * 0) = src_color * dst_color

sceGuBlendFunc(GU_ADD, GU_ZERO, GU_SRC_COLOR, 0, 0);
= (src_color * 0) + (dst_color * src_color) = dst_color * src_color

Both should have indentical results.

Your problem is that "GU_ZERO" is not a proper blending function. You should use GU_FIX instead (with fix parameter 0. "GU_ONE" would have fix parameter 0xffffffff).

Both of these work as you intented (give you the multiply alpha you want):
sceGuBlendFunc(GU_ADD, GU_FIX, GU_SRC_COLOR, 0, 0);
sceGuBlendFunc(GU_ADD, GU_DST_COLOR, GU_FIX, 0, 0);

And this gives you basic additive alpha (src_color * 1 + dst_color * 1):
sceGuBlendFunc(GU_ADD, GU_FIX, GU_FIX, 0xffffff, 0xffffff);

[chp]

If you look at pspgu.h, you will see the following: