Antialiasing a filled tessellated shape?

[Bob]

I created a minimal test program. Here is the result:

http://www.hindbrain.net/example.jpg

Is there a way to get less ragged edges on such a shape?
Here's the essential code:

GLdouble shape[4][3] = {
{-3, 3.8, 0},
{ 0, 3.0, 0},
{ 3, 3.8, 0},
{ 0, 3.7, 0}
};

int InitGL(GLvoid) {
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClearDepth(1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
return TRUE;
}

GLuint compile(void) {
GLuint id = glGenLists(1);

if(!id) return id;

GLUtesselator *tess = gluNewTess();
if(!tess) return 0;

gluTessCallback(tess, GLU_TESS_BEGIN, (void (CALLBACK *)())
tessBeginCB);
gluTessCallback(tess, GLU_TESS_END, (void (CALLBACK *)())tessEndCB);
gluTessCallback(tess, GLU_TESS_ERROR, (void (CALLBACK *)())
tessErrorCB);
gluTessCallback(tess, GLU_TESS_VERTEX, (void (CALLBACK *)())
tessVertexCB);

glNewList(id, GL_COMPILE);
glColor3ub(0, 255, 255);
gluTessBeginPolygon(tess, 0);
gluTessBeginContour(tess);
gluTessVertex(tess, shape[0], shape[0]);
gluTessVertex(tess, shape[1], shape[1]);
gluTessVertex(tess, shape[2], shape[2]);
gluTessVertex(tess, shape[3], shape[3]);
gluTessEndContour(tess);
gluTessEndPolygon(tess);
glEndList();

gluDeleteTess(tess);

return id;
}

int draw(GLvoid) {

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();

glTranslatef(0.0f, -3.5f, -6.0f);

glEnable( GL_BLEND );
glEnable(GL_POLYGON_SMOOTH);
glCallList(listId1);
glDisable(GL_POLYGON_SMOOTH);
glDisable( GL_BLEND );

return TRUE;
}

thanks,
Bob

[Andy V]

On Dec 29, 9:55 am, Bob <b...@xyzzy.net> wrote:
> I created a minimal test program. Here is the result:
>
> http://www.hindbrain.net/example.jpg
>
> Is there a way to get less ragged edges on such a shape?
> Here's the essential code:
>

Use full screen anti-aliasing rather than polygon smoothing.

If you must use polygon smoothing, use the correct blend method (src
alpha saturate, one) and order your polygons from front to back.

--
Andy V

[fungus]

On Dec 29, 3:55 pm, Bob <b...@xyzzy.net> wrote:
> I created a minimal test program. Here is the result:
>
> http://www.hindbrain.net/example.jpg
>
> Is there a way to get less ragged edges on such a shape?
>

You need to enable full-screen antialiasing, this is done
when you create the window so how you do it will depend
on whatever you're using to make your windows. Basically
you choose a pixel format with multisampling.

Whatever you do don't try to use polygon smoothing, it's
obsolete and opens up a world of pain.

--
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