Thread: blending problems with OpenGL

  1. 09-21-2010 #1
    jbhinc
    jbhinc is offline
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    blending problems with OpenGL

    im working on a simple 3d world and i am using bitmap images... i wanted to make a door/window that is masked so that you can see thru the black areas of the mask... everything works except when you behind another wall you can still see the door from across the world.... i hope this makes sense. i would rather use bitmaps in this particular program. i know .tga's would be ideal but i dont want to go that route. can someone please tell me what im doing wrong?

    Code:
    int InitGL(GLvoid)										// All Setup For OpenGL Goes Here
{
	if (!LoadGLTextures())								// Jump To Texture Loading Routine
	{
		return FALSE;									// If Texture Didn't Load Return FALSE
	}

	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);				// Clear The Background Color To Black
	glClearDepth(1.0);									// Enables Clearing Of The Depth Buffer
	glEnable(GL_DEPTH_TEST);							// Enable Depth Testing
	glShadeModel(GL_SMOOTH);							// Enables Smooth Color Shading
	glEnable(GL_TEXTURE_2D);							// Enable 2D Texture Mapping
	//glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	// Really Nice Perspective Calculations

	return TRUE;										// Initialization Went OK
}

int DrawGLScene(GLvoid)									// Here's Where We Do All The Drawing
{


	srand(time(NULL));
	int k = 0;

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear The Screen And The Depth Buffer
	glLoadIdentity();									// Reset The View

// yrot = yrot+180;
	if (lookupdown > 60) lookupdown = 60;
	if (lookupdown < -60) lookupdown = -60;
	glBindTexture(GL_TEXTURE_2D, texture[4]);
	glRotatef(lookupdown,1.0f,0,0);
	glRotatef(yrot,0.0f,1.0f,0.0f);
	
	glTranslated(x,0.0,z);

	glBegin(GL_QUADS);
		// Top Face
		glNormal3f( 0.0f,1.0f, 0.0f);
		glTexCoord2f(20.0f, 20.0f); glVertex3f(-20.0f, 0.75f, -20.0f);
		glTexCoord2f(0.0f, 20.0f); glVertex3f( -2.0f, 0.75f, -20.0f);
		glTexCoord2f(0.0f, 0.0f); glVertex3f( -2.0f, 0.75f,  -2.0f);
		glTexCoord2f(20.0f, 0.0f); glVertex3f(-20.0f, 0.75f,  -2.0f);
	glEnd();

	glBindTexture(GL_TEXTURE_2D, texture[4]);
	glBegin(GL_QUADS);
		// Bottom Face
		glNormal3f( 0.0f,-1.0f, 0.0f);
		glTexCoord2f(20.0f, 20.0f); glVertex3f(-20.0f, -0.75f, -20.0f);
		glTexCoord2f(0.0f, 20.0f); glVertex3f( -2.0f, -0.75f, -20.0f);
		glTexCoord2f(0.0f, 0.0f); glVertex3f( -2.0f, -0.75f,  -2.0f);
		glTexCoord2f(20.0f, 0.0f); glVertex3f(-20.0f, -0.75f,  -2.0f);
	glEnd();

	glTranslatef(-19.0f,0.0f,-19.0f);
	
	for(int i = 0; i < 9; i++)
	{
		for(int j = 0; j < 10; j++)
		{


			if(matrix[k] == 2)
			{
				glBindTexture(GL_TEXTURE_2D, texture[3]);

				glBegin(GL_QUADS);
					// Front Face
					//glNormal3f( 0.0f, 0.0f, 1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					// Back Face
					//glNormal3f( 0.0f, 0.0f,-1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					// Right face
					//glNormal3f( 1.0f, 0.0f, 0.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					// Left Face
					//glNormal3f(-1.0f, 0.0f, 0.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
				glEnd();

			}
			if(matrix[k] == 1)
			{
					glBindTexture(GL_TEXTURE_2D, texture[6]);
				glBegin(GL_QUADS);
					// Front Face
					glNormal3f( 0.0f, 0.0f, 1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					// Back Face
					glNormal3f( 0.0f, 0.0f,-1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					// Right face
					glNormal3f( 1.0f, 0.0f, 0.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					// Left Face
					glNormal3f(-1.0f, 0.0f, 0.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
				glEnd();				
			}
						if(matrix[k] == 3)
			{



				glBindTexture(GL_TEXTURE_2D, texture[5]);

				glEnable(GL_BLEND);									// Enable Blending
	            glDisable(GL_DEPTH_TEST);							// Disable Depth Testing
	            glBlendFunc(GL_DST_COLOR,GL_ZERO);				// Blend Screen Color With Zero (Black)
				glBegin(GL_QUADS);
					// Front Face
					//glNormal3f( 0.0f, 0.0f, 1.0f);
					//glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					//glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					//glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					//glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					// Back Face
					glNormal3f( 0.0f, 0.0f,-1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					// Right face
					//glNormal3f( 1.0f, 0.0f, 0.0f);
					//glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					//glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					//glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					//glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					// Left Face
					//glNormal3f(-1.0f, 0.0f, 0.0f);
					//glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					//glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					//glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					//glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
				glEnd();



	

					glBindTexture(GL_TEXTURE_2D, texture[2]);
                    glBlendFunc(GL_ONE, GL_ONE);					// Copy Image 1 Color To The Screen
	
					glBegin(GL_QUADS);
					// Front Face
					//glNormal3f( 0.0f, 0.0f, 1.0f);
					//glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					//glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					//glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					//glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					// Back Face
					glNormal3f( 0.0f, 0.0f,-1.0f);
					glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					// Right face
					//glNormal3f( 1.0f, 0.0f, 0.0f);
					//glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -0.75f, -1.0f);
					//glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  0.75f, -1.0f);
					//glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  0.75f,  1.0f);
					//glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -0.75f,  1.0f);
					// Left Face
					//glNormal3f(-1.0f, 0.0f, 0.0f);
					//glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -0.75f, -1.0f);
					//glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -0.75f,  1.0f);
					//glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  0.75f,  1.0f);
					//glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  0.75f, -1.0f);
				glEnd();
				
				
              	glEnable(GL_DEPTH_TEST);							// Enable Depth Testing
	            glDisable(GL_BLEND);								// Disable Blendin

			}
			k++;
			glTranslatef(2.0f,0.0f,0.0f);
		}
		glTranslatef(-20.0f,0.0f,2.0f);
	}

	return TRUE;// Keep Going
}
    Last edited by Salem; 09-21-2010 at 09:11 AM. Reason: snipped email address
  2. 09-21-2010 #2
    GReaper
    GReaper is offline
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    You should add alpha testing and pass the alpha function the options GL_GREATER and GL_ZERO ( i think )...
    Devoted my life to programming...
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