gluSphere transparent background

[Simon666]

Attachment 33627

Hi all,

for my program I want to try something new, I would like to draw a transparent sphere with a smaller non transparent one inside, as illustrated. Any idea how to do this?

All I can do, is some blending when the sphere is behind an object, but I can't make it really blend when it is in the foreground. Below is the code I currently use for drawing the sphere.

 // Draw a sphere at the position of the node

 GLfloat ambient1[]	 = {0.5f, 0.5f,0.5f,1.0f};
 GLfloat ambient2[]	 = {0.2f, 0.2f,0.2f,1.0f};
 GLfloat diffuse[]	 = {0.7f, 0.7f,0.7f,1.0f};
 GLfloat position1[] = {0.0f,-1.0f,0.0f,0.0f};
 GLfloat position2[] = {0.0f, 1.0f,0.0f,0.0f};
 GLfloat spec[]		 = {1.0f, 1.0f,1.0f,1.0f};
 GLfloat specma[]	 = {1.0f, 1.0f,1.0f,1.0f};

 glShadeModel(GL_SMOOTH);						// Smooth rendering
 glFrontFace(GL_CCW);							// Counter clock-wise polygons face out

 glEnable(GL_DEPTH_TEST);						// Hidden surface removal
 glEnable(GL_LIGHTING);							// Enable lighting

 glEnable(GL_POLYGON_OFFSET_FILL);				// Correction for small errors
 glPolygonOffset(0.5, 2.0);

 glLightModelfv(GL_LIGHT_MODEL_AMBIENT,ambient1);
 glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER,1);
 glLightfv(GL_LIGHT0,GL_POSITION,position1);	// Setup and enable light 0
 glLightfv(GL_LIGHT0,GL_AMBIENT,ambient2);
 glLightfv(GL_LIGHT0,GL_DIFFUSE,diffuse);
 glLightfv(GL_LIGHT0,GL_SPECULAR,spec);
 glEnable(GL_LIGHT0);
 glLightfv(GL_LIGHT1,GL_POSITION,position2);	// Setup and enable light 1
 glLightfv(GL_LIGHT1,GL_AMBIENT,ambient2);
 glLightfv(GL_LIGHT1,GL_DIFFUSE,diffuse);
 glLightfv(GL_LIGHT1,GL_SPECULAR,spec);
 glEnable(GL_LIGHT1);

 glEnable(GL_COLOR_MATERIAL);					// Set Material properties to follow glColor values
 glColorMaterial(GL_FRONT,GL_AMBIENT_AND_DIFFUSE);
 glMaterialfv(GL_FRONT,GL_SPECULAR,specma);
 glMateriali(GL_FRONT,GL_SHININESS,128);

 glColor4d(0,0,1,0.150);

 GLUquadricObj *quadric=gluNewQuadric();

 gluQuadricNormals(quadric, GLU_SMOOTH);

 glTranslated( P.x, P.y, P.z );

 double radius = 0.002;
 
 gluSphere(quadric,radius,50,50);

 glEnable( GL_BLEND );
 glDisable(GL_DEPTH_TEST);
 glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );

 gluSphere(quadric,radius,50,50);

 glEnable(GL_DEPTH_TEST);

 glTranslated(-P.x,-P.y,-P.z );

 gluDeleteQuadric(quadric);

 //// restore rendering context //

 glDisable(GL_POLYGON_OFFSET_FILL);
 glDisable(GL_COLOR_MATERIAL);
 glDisable(GL_LIGHTING);
 glDisable(GL_LIGHT1);
 glDisable(GL_LIGHT0);
 glDisable(GL_BLEND);