A Problem in drawing 2D transparent shapes with ortho

Graphics and GPU Programming Programming OpenGL

Started by Graphic_Programmer August 09, 2012 11:30 AM

4 comments, last by Graphic_Programmer 11 years, 8 months ago

107

Author

August 09, 2012 11:30 AM

First, my English isn't very good, i can say wrong words so sorry.
I am beginner to making 2D/3D Graphics in Opengl and i have a problem about drawing 3D shapes under 2D ortho graphics with alpha transparent.
The ScreenShot

I don't know could i tell. I think you understood my problem from the picture.
These are my drawing codes;



ciz()

{

glViewport(0,0,ewidth,eheight);

glMatrixMode(GL_PROJECTION);

  glLoadIdentity();

   glPushMatrix();

    glOrtho(-1,1,-1,1,-20,20);

glMatrixMode(GL_MODELVIEW);

  glLoadIdentity();

    glColor4f(1,1,0,1);

    glDisable(GL_TEXTURE_2D);

glPushMatrix();

glTranslatef(((float)mouse_x-(ewidth/2))/(ewidth/2),-((float)mouse_y-(eheight/2))/(eheight/2),0.1);

glBindTexture(GL_TEXTURE_2D,NULL);

    glBegin(GL_POLYGON);

    for(i=0; i<20; i++)

{

	 glVertex3f(cos(18*i*pi/180)/32,sin(18*i*pi/180)/32,0);

}

glEnd();  

glColor4f(1,1,1,1);

glEnable(GL_TEXTURE_2D);

glBindTexture(GL_TEXTURE_2D,tex[0]);

glPopMatrix();

   /* glBegin(GL_QUADS);

    glTexCoord2i(0,0); glVertex3f(-0.9,0.9,0);

glTexCoord2i(1,0); glVertex3f(-0.6,0.9,0);

glTexCoord2i(1,1); glVertex3f(-0.6,0.6,0);

glTexCoord2i(0,1); glVertex3f(-0.9,0.6,0);

glEnd();



   glBegin(GL_QUADS);

    glTexCoord2i(0,0); glVertex3f(-0.6,0.9,0);

glTexCoord2i(1,0); glVertex3f(-0.3,0.9,0);

glTexCoord2i(1,1); glVertex3f(-0.3,0.6,0);

glTexCoord2i(0,1); glVertex3f(-0.6,0.6,0);

glEnd();*/

//glDisable(GL_BLEND);

//glDisable(GL_DEPTH_TEST);

glBindTexture(GL_TEXTURE_2D,tex[1]);

glBegin(GL_QUADS);

for(i=0,j=0; i<=yazi_uz; i++)

{

  if(yazi=='A')

  {

   ii=0;

   jj=0;

   glTexCoord2f((1+(float)ii+(float)ii*13)/512,(1+(float)jj+(float)jj*18)/256); glVertex3f(((0+(float)i*50 )/640)*2-1,-(((0+(float)j*80 )/480)*2-1),0);

   glTexCoord2f((1+(float)ii+((float)ii+1)*13)/512,(1+(float)jj+(float)jj*18)/256); glVertex3f(((0+((float)i+1)*50 )/640)*2-1,-(((0+(float)j*80 )/480)*2-1),0);

   glTexCoord2f((1+(float)ii+((float)ii+1)*13)/512,(1+(float)jj+((float)jj+1)*18)/256); glVertex3f(((0+((float)i+1)*50 )/640)*2-1,-(((0+((float)j+1)*80 )/480)*2-1),0);

   glTexCoord2f((1+(float)ii+(float)ii*13)/512,(1+(float)jj+((float)jj+1)*18)/256); glVertex3f(((0+(float)i*50 )/640)*2-1,-(((0+((float)j+1)*80 )/480)*2-1),0);

  }

}

glEnd();

glEnable(GL_DEPTH_TEST);

glMatrixMode(GL_PROJECTION);

  glLoadIdentity();

   glPopMatrix();

    gluPerspective(45,(float)(ewidth/eheight),.1,1000);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();



gluLookAt(c_x+cos((dir+180)*pi/180)*cos(-der*pi/180)*uz,c_y+sin((dir+180)*pi/180)*cos(-der*pi/180)*uz,c_z+sin(-der*pi/180)*uz,c_x,c_y,c_z, 0,1,0);

glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);

glColor3f(1,1,1);

//glDisable(GL_TEXTURE_2D);

/* glBegin(GL_POLYGON);

glTexCoord2i(0,0);

glVertex3f(-15,15,0);

glTexCoord2i(1,0);

glVertex3f(15,15,0);

glTexCoord2i(1,1);

glVertex3f(15,-15,0);

glTexCoord2i(0,1);

glVertex3f(-15,-15,0);

glEnd();*/

//glEnable(GL_TEXTURE_2D);

/*glBegin(GL_TRIANGLES);

for(i=0; i<10; i++)

{

  glNormal3f(cos((i+0.5)*36*pi/180)*cos(90-atan(10/7)*pi/180),sin((i+0.5)*36*pi/180)*cos(90-atan(10/7)*pi/180),sin(90-atan(10/7)*pi/180));

  glVertex3f(0,0,5);

  glVertex3f(cos(36*i*pi/180)*7,sin(36*i*pi/180)*7,-5);

  glVertex3f(cos(36*(i+1)*pi/180)*7,sin(36*(i+1)*pi/180)*7,-5);

}

glEnd();*/

glColor4f(1,1,1, 1);

//glDisable(GL_DEPTH_TEST);

//glDepthMask(GL_TRUE);

//glEnable(GL_ALPHA_TEST);

    glBindTexture(GL_TEXTURE_2D, tex[2]);



glPushMatrix();

glTranslatef(obj[0].x,obj[0].y,obj[0].z);

glScalef(0.5,0.5,0.5);

glRotatef(der2*5,0.7,0.3,0.5);

//glBindTexture(GL_TEXTURE_2D,tex[1]);

glBegin(GL_QUADS);

//alt

glNormal3f(0,0,-1);

glTexCoord2i(0,0);

glVertex3f(-8,8,-8);

glTexCoord2i(1,0);

glVertex3f(8,8,-8);

glTexCoord2i(1,1);

glVertex3f(8,-8,-8);

glTexCoord2i(0,1);

glVertex3f(-8,-8,-8);

//üst

glNormal3f(0,0,1);

glTexCoord2i(0,0);

glVertex3f(-8,8,8);

glTexCoord2i(1,0);

glVertex3f(8,8,8);

glTexCoord2i(1,1);

glVertex3f(8,-8,8);

glTexCoord2i(0,1);

glVertex3f(-8,-8,8);

//sa?

glNormal3f(1,0,0);

glTexCoord2i(0,0);

glVertex3f(8,8,-8);

glTexCoord2i(1,0);

glVertex3f(8,8,8);

glTexCoord2i(1,1);

glVertex3f(8,-8,8);

glTexCoord2i(0,1);

glVertex3f(8,-8,-8);

//sol

glNormal3f(-1,0,0);

glTexCoord2i(0,0);

glVertex3f(-8,8,-8);

glTexCoord2i(1,0);

glVertex3f(-8,8,8);

glTexCoord2i(1,1);

glVertex3f(-8,-8,8);

glTexCoord2i(0,1);

glVertex3f(-8,-8,-8);

//yukar?

glNormal3f(0,1,0);

glTexCoord2i(0,0);

glVertex3f(-8,8,8);

glTexCoord2i(1,0);

glVertex3f(8,8,8);

glTexCoord2i(1,1);

glVertex3f(8,8,-8);

glTexCoord2i(0,1);

glVertex3f(-8,8,-8);

//a?a??

glNormal3f(0,-1,0);

glTexCoord2i(0,0);

glVertex3f(-8,-8,8);

glTexCoord2i(1,0);

glVertex3f(8,-8,8);

glTexCoord2i(1,1);

glVertex3f(8,-8,-8);

glTexCoord2i(0,1);

glVertex3f(-8,-8,-8);

glEnd();

glPopMatrix();

glEnable(GL_DEPTH_TEST);

/* glClearColor(1,0,0,1);

   glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);*/

//resim_yukle("font.bmp");

SDL_GL_SwapBuffers();

}

Help please, Thanks for your helps.

Lazy Foo

1,113

August 09, 2012 11:46 AM

You need to enable blending, set your blending calculation, and you should probably disable depth testing as it doesn't mix will with alpha blending.

You probably want this somewhere in your initialization code:
[source lang="cpp"]glEnable( GL_BLEND );
glDisable( GL_DEPTH_TEST );
glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );[/source]
I got a tutorial on blending and transparency with OpenGL

Learn to make games with my SDL 2 Tutorials

Graphic_Programmer

107

Author

August 09, 2012 12:13 PM

You need to enable blending, set your blending calculation, and you should probably disable depth testing as it doesn't mix will with alpha blending.

You probably want this somewhere in your initialization code:
[source lang="cpp"]glEnable( GL_BLEND );
glDisable( GL_DEPTH_TEST );
glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );[/source]
I got a tutorial on blending and transparency with OpenGL

Yes, i know but when i put glDisable(GL_DEPTH_TEST) to initialization, the red box looked on the transparent letter "A"(my 2D Ortho graphic).I think, the box must be under the 2D letter.
This is screenshot when i put glDisable(GL_DEPTH_TEST);

Lazy Foo

1,113

August 09, 2012 12:34 PM

In that case you want to
1) Draw your 3D scene first with depth buffer enabled.
2) Clear/Disable the depth buffer and enable blending.
3) Draw the text over the 3D scene.
4) Swap buffers to update the screen.

Learn to make games with my SDL 2 Tutorials

Graphic_Programmer

107

Author

August 09, 2012 12:39 PM

In that case you want to
1) Draw your 3D scene first with depth buffer enabled.
2) Clear/Disable the depth buffer and enable blending.
3) Draw the text over the 3D scene.
4) Swap buffers to update the screen.

Do you think i must change 2-3 and 1? OK i will try

Graphic_Programmer

107

Author

August 09, 2012 12:48 PM

I made it.
Thank you very much!

A Problem in drawing 2D transparent shapes with ortho

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A Problem in drawing 2D transparent shapes with ortho

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