Jump to content
  • Advertisement
Sign in to follow this  
Thirthe

simple blending problem

This topic is 3735 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hello all! I've just went through the 8th NeHe's lesson(blending) and it seems that when I change the alpha values in glColor4f() funct, nothing changes the scene! I have fiddled around with different blending functions and sorted the polys from farthest to nearest, but still nothing changes the transparency of the (two) polys in the scene. I have a gf2mx, the latest glext.h and the latest drivers installed. Also, glGetError() reports that there were no errors. relevant functions:
void init( char *a )
{
    glClearColor( 0.6f, 0.8f, 0.2f, 0.0f );

    glShadeModel( GL_SMOOTH );
    glEnable(GL_DEPTH_TEST);

    glDepthFunc(GL_LEQUAL);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE);

    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

    init_VBO();
    load_tex( a );
    init_light();
}

void init_light()
{
    GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat mat_shininess[] = { 10.0 };
    GLfloat white_light[] = { 1.0, 1.0, 0.5, 1.0 };
    GLfloat lmodel_ambient[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat light_position[] = { -6.0, 7.0, 6.0, 1.0 };

    glLightfv(GL_LIGHT0, GL_DIFFUSE, white_light);
    glLightfv(GL_LIGHT0, GL_SPECULAR, white_light);

    glLightfv(GL_LIGHT0, GL_POSITION, light_position);

    //glLightfv(GL_LIGHT0, GL_AMBIENT, white_light);    //similar?
    glLightModelfv( GL_LIGHT_MODEL_AMBIENT, lmodel_ambient );

    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);

}

static void display(void)
{
    glMatrixMode( GL_MODELVIEW ); // do NOT switch MatrixMode every frame!
    glLoadIdentity();   // do NOT loadidentity ever frame (use push/popmatrix instead)

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glBindBuffer( GL_ARRAY_BUFFER, VBO );
    glBindTexture( GL_TEXTURE_2D, tex[tex_id] );

    glVertexPointer( 3, GL_FLOAT, sizeof(GLfloat)*5, BUFFER_OFFSET(0) );		// Set The Vertex Pointer To The Vertex Buffer
    glTexCoordPointer( 2, GL_FLOAT, sizeof(GLfloat)*5, BUFFER_OFFSET( sizeof(GLfloat)*3 ) );

    glColor3f( 1.f, 1.f, 1.f );


    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);

    glEnable (GL_TEXTURE_2D);
    glEnableClientState( GL_VERTEX_ARRAY );
    glEnableClientState( GL_TEXTURE_COORD_ARRAY );

    glDrawArrays( GL_QUADS, 0, 4 ); // 4 == vertex count

    glDisableClientState( GL_TEXTURE_COORD_ARRAY );
    glDisableClientState( GL_VERTEX_ARRAY );
    glDisable (GL_TEXTURE_2D);

    //glDisable(GL_DEPTH_TEST);
    glEnable( GL_BLEND );

    glTranslatef( 0.f, 2.f, 0.f );
    glColor4f( 1.f, 0.f, 1.f, 1.0f );
    glutSolidCube( 4.0 );

    glColor4f( 0.f, 0.f, 1.f, 1.0f );
	glBegin(GL_QUADS);

        // quick trick: 1.f(normal) is where the column of numbers(vertex) are the same!
        glNormal3f( 0.f, 1.f, 0.f );
		glVertex3f( 4.0f, 4.0f,-4.0f);					// Top Right Of The Quad (Top)
		glVertex3f(-4.0f, 4.0f,-4.0f);					// Top Left Of The Quad (Top)
		glVertex3f(-4.0f, 4.0f, 4.0f);					// Bottom Left Of The Quad (Top)
		glVertex3f( 4.0f, 4.0f, 4.0f);					// Bottom Right Of The Quad (Top)

        glNormal3f( 0.f, -1.f, 0.f );
		glVertex3f( 4.0f,-4.0f, 4.0f);					// Top Right Of The Quad (Bottom)
		glVertex3f(-4.0f,-4.0f, 4.0f);					// Top Left Of The Quad (Bottom)
		glVertex3f(-4.0f,-4.0f,-4.0f);					// Bottom Left Of The Quad (Bottom)
		glVertex3f( 4.0f,-4.0f,-4.0f);					// Bottom Right Of The Quad (Bottom)

        glNormal3f( 0.f, 0.f, 1.f );
		glVertex3f( 4.0f, 4.0f, 4.0f);					// Top Right Of The Quad (Front)
		glVertex3f(-4.0f, 4.0f, 4.0f);					// Top Left Of The Quad (Front)
		glVertex3f(-4.0f,-4.0f, 4.0f);					// Bottom Left Of The Quad (Front)
		glVertex3f( 4.0f,-4.0f, 4.0f);					// Bottom Right Of The Quad (Front)

        glNormal3f( 0.f, 0.f, -1.f );
		glVertex3f( 4.0f,-4.0f,-4.0f);					// Top Right Of The Quad (Back)
		glVertex3f(-4.0f,-4.0f,-4.0f);					// Top Left Of The Quad (Back)
		glVertex3f(-4.0f, 4.0f,-4.0f);					// Bottom Left Of The Quad (Back)
		glVertex3f( 4.0f, 4.0f,-4.0f);					// Bottom Right Of The Quad (Back)

        glNormal3f( -1.f, 0.f, 0.f );
		glVertex3f(-4.0f, 4.0f, 4.0f);					// Top Right Of The Quad (Left)
		glVertex3f(-4.0f, 4.0f,-4.0f);					// Top Left Of The Quad (Left)
		glVertex3f(-4.0f,-4.0f,-4.0f);					// Bottom Left Of The Quad (Left)
		glVertex3f(-4.0f,-4.0f, 4.0f);					// Bottom Right Of The Quad (Left)

        glNormal3f( 1.f, 0.f, 0.f );
		glVertex3f( 4.0f, 4.0f,-4.0f);					// Top Right Of The Quad (Right)
		glVertex3f( 4.0f, 4.0f, 4.0f);					// Top Left Of The Quad (Right)
		glVertex3f( 4.0f,-4.0f, 4.0f);					// Bottom Left Of The Quad (Right)
		glVertex3f( 4.0f,-4.0f,-4.0f);					// Bottom Right Of The Quad (Right)
	glEnd();											// Done Drawing The Pyramid

    glDisable( GL_BLEND );
    //glEnable(GL_DEPTH_TEST);

    glDisable(GL_LIGHTING);
    glDisable(GL_LIGHT0);


    glutSwapBuffers();

}

btw, with this code, even with alpha values set to 1.0f in glColor4f(), it makes the two polys transparent. Thank you!

Share this post


Link to post
Share on other sites
Advertisement
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!