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GL_QUADS and a shiny black screen


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#1   Members   -  Reputation: 122

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Posted 08 August 2001 - 08:28 AM

Hi people, I''m using OpenGL ortho mode and wanna display a simple quad with a color and an alpha value. So far so good, but everything I get is a black screen. The code seems right to me....could anybode please help!?? void cSprite:lane(RECT dim,float r,float g,float b,float alpha) { glLoadIdentity(); glTranslatef((float)dim.left,(float)dim.top,0.0f); glColor4f(r,g,b,alpha); glBegin(GL_QUADS); glVertex2d(0,dim.bottom); // top left glVertex2d(0,0); // bottom left glVertex2d(dim.right,0); // top right glVertex2d(dim.right,dim.bottom); // bottom right glEnd(); } I''m calling the function with these params: rc.left=0; rc.top=0; rc.right=640; rc.bottom=480; Sprite->Plane(rc,1.0f,1.0f,1.0f,0.0f); thanks! Bye, Alex

#2   Members   -  Reputation: 1087

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Posted 08 August 2001 - 10:33 AM

Using 0.0f for an alpha value makes the object invisible. Also, you might want to set up a method of blending.

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#3   Members   -  Reputation: 187

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Posted 08 August 2001 - 11:01 AM

I think the problem might be that smiley face in your function definition

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Posted 08 August 2001 - 11:33 AM

glClearColor(1,0,0,1);
if u see a pure red screen then the object cant be seen
perhaps the cameras pointing the wrong way or the backface is facing the camera etc.
if u do see a black square perhaps u have lighting enabled


#5   Members   -  Reputation: 122

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Posted 09 August 2001 - 12:39 AM

Hi,

I set the background to red but I''m getting a black one -> the quad is drawn but don''t uses the color....

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Posted 13 August 2001 - 08:24 PM

Try translating behind the front clipping plane. If your front clipping plane is at 1.0, translate to 1.1.

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Posted 14 August 2001 - 09:48 AM

have you disabled lighting , blending and texturing?




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