Transparency problems with blending and alpha

Kiroke · 2002-01-29T13:26:20

hi there i got quite a problem here I got a bit of code that uses blend and alpha value to do transparency. The problem is that things that shouldnt be transparent ARE and things that should be BEHIND objects are draw BEFORE them. I suspect that has somthing to do with the depth buffer but i cant see whats wrong. Heres are samples of my code : //initialize... glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glEnable(GL_DEPTH_TEST); glEnable(GL_CULL_FACE); glFrontFace(GL_CW); glShadeModel(GL_SMOOTH); glBlendFunc(GL_SRC_ALPHA,GL_ONE); //lighning code here...i tested it quite alot and it works now //draw code... glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); glColor4f(1.0f, 1.0f, 1.0f, 1.0f); //draw a sphere without light glDisable(GL_LIGHTING); //drawing glu sphere here glEnable(GL_LIGHTING); //draw a rectangle supposed to be behind things becauz of the -0.1 in the translatef glColor4f(1.0f, 0.0f, 0.0f, 1.0f); glTranslatef(bonuses.x, bonuses[i].y, -0.1f); //draw rectangle here //draw a big rectangle behind of all things that is supposed to be opaque and that is TRANSPARENT ?!?!?! glColor4f(0.0f, 1.0f, 0.0f, 1.0f); //draw big rectangle here //Beginning drawing transparent stuff // glEnable(GL_BLEND); //read only mode for the depth buffer glDepthMask(GL_FALSE); //draw blocks BEFORE all the scene... oneBlock.alpha is sometimes 1.0, somtimes 0.5 glColor4f(1.0f, 1.0f, 1.0f, oneBlock.alpha); //draw blocks here glDepthMask(GL_TRUE); glEnable(GL_DEPTH_TEST); glFlush(); SwapBuffers(g_HDC); I really cant see the problem... the big rectangle is semi-transparent and appears to be BEFORE almost all the other objects. The rectangle though appears with full color before the big rectangle. To make it short, the big rectangle should be behind all and opaque. The rectangle should be just before that The blocks should be cefore the rectangle and somtimes transparent. Thats about all...tell me if you see somthing its been a week and i cant find the solution :-( Kiroke

NeHe Productions Affiliates

Started by Kiroke January 27, 2002 09:23 PM

11 comments, last by Kiroke 23 years ago

Kiroke

Author

122

January 28, 2002 11:26 AM

Ok thx ill try that at home:-)

And thx alot for your help... ur kinda good at helping ppl here.

Kirokewww.geocities.com/kiroke2

Kiroke

Author

122

January 28, 2002 06:28 PM

I tried that at home and it still wont works... I putted glDisable(GL_BLEND); right at the place vincoof told me and it still does the same problem. I tried combinaisons of glEnable() and glDisable() at some places in the code and it still wont change anything... its really strange.

Anyone have an idea??

Kirokewww.geocities.com/kiroke2

vincoof

514

January 29, 2002 01:26 PM

Well, if I understood your problem well that would have corrected it.

Could you post a snapshot please ?
It might help, with some of your comments of what you would like to see and where this does not satisfy you.

Transparency problems with blending and alpha

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