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blend func problem

Started by stryx Nov 30, 2002 at 12:28 PM 2 replies 550+ views

Original Post

Nov 30, 2002 at 12:28 PM

Hi, NeHe Bitmapfonts work fine, but in my current project I''ve got a white background, so the text doesn''t show. I tried to change the blend func to "the right" but I haven''t found it yet. Does anyxbody know how to render Black,Bitmapfonts on white background ? plz help, thx, stryx

PmanC

Nov 30, 2002 at 1:28 PM

just inverse the colors in NeHe''s bitmap. i think that would work. -PmanC

stryx

Dec 1, 2002 at 5:48 AM

I tried it, but it doesn''t work, because the color is already white, so the blending doesn''t darken it.

The problem is that i get only lighten-modes.
Blending makes the pictures lighter but not darken ;(

hali

Dec 1, 2002 at 6:08 AM

you can do it in 2 ways:

1.
inverse the colors in font bitmap and use GL_EXT_BLEND_MINMAX extension:

glBlendEquationEXT(GL_MIN_EXT);
// here render fonts
glBlendEquationEXT(GL_FUNC_ADD_EXT);

2.
or dont inverse the colors in font bitmap and use GL_EXT_BLEND_SUBTRACT extension:

glBlendEquationEXT(GL_FUNC_REVERSE_SUBTRACT_EXT);
glBlendFunc(GL_ONE,GL_ONE);
// here render fonts
glBlendEquationEXT(GL_FUNC_ADD_EXT);

hope it helps

hali

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