Vertex arrays ?

Graphics and GPU Programming Programming

Started by Lanman February 05, 2002 06:32 AM

10 comments, last by Lanman 22 years, 1 month ago

122

Author

February 05, 2002 06:32 AM

Hi there ! I''ve heared something about vertex arays. Is it faster ? I guess so. So, I need to know how to do it... I''ve read (in this forum some time ago) that its not good (and fast) to call glVertex3f may times. I don''t know what vertex array looks like. I imagine that it would look like normal array. But i don''t know how to tell OpenGL to draw vertexes from this array. I''ve tried to find something looking like this in gl.h but i didn''t find anything. I imagine that the command would look like glVertexnf( ... ). I just don''t know how to do it...please help me.Send me any www or good tut how to do it. Thanks !!!

Null and Void

1,088

February 05, 2002 07:25 AM

Look up:

glDrawArrays

glDrawElements

glVertexPointer

And glColorPointer, glNormalPointer, and glTexCoordPointer.

quote:Original post by Lanman
Is it faster?

Yes

Fritz3D

122

February 05, 2002 09:13 AM

I can''t understand one thing about vertex arrays:

can I use them for drawing for instance several cubes with non-smooth sides? All I have read says they are good for tristrips and nothing more.

invective

118

February 05, 2002 01:50 PM

quote:
can I use them for drawing for instance several cubes with non-smooth sides? All I have read says they are good for tristrips and nothing more

Yes. You can use them to draw GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES, GL_QUAD_STRIP, GL_QUADS, and GL_POLYGON.

Do not share vertex normals along edges for faceted things like cubes. Use 2 GL_TRIANGLES or 1 GL_QUADS per face, instead of sharing vertices with GL_TRIANGLE_STRIP or GL_QUAD_STRIP.

Lanman

122

Author

February 05, 2002 02:27 PM

Thanx!!!
Well, finaly I know the command to draw the array...BUT there''s one more thing that I don''t know...how to set up the array (sorry for the newbie question...I''m not a newbie, I''m programming sice my 10 years but I''m triing to work with OpenGL for only less than year)...where can I find an example code...PLEASE...THANX!THANX!THANX! You are probably pissed off when you see every day my new stupid question, huh ?
But thanx !

Null and Void

1,088

February 05, 2002 03:53 PM

To draw a square (with an extra z coordinate for no reason):

  float Data[] = { -1.0f, -1.0f, 0.0f,                 -1.0f,  1.0f, 0.0f,                  1.0f,  1.0f, 0.0f,                  1.0f, -1.0f, 0.0f };glVertexPointer(3,GL_FLOAT,0,Data);glDrawArrays(GL_QUAD, 0, 1);

You should also lookup glEnableClientState and glDisableClientState (I forgot about them last time) to use more than just vertices (i.e. to add textures, colors, or normals).

Fritz3D

122

February 05, 2002 09:33 PM

quote:Original post by invective
Yes. You can use them to draw GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLES, GL_QUAD_STRIP, GL_QUADS, and GL_POLYGON.

Do not share vertex normals along edges for faceted things like cubes. Use 2 GL_TRIANGLES or 1 GL_QUADS per face, instead of sharing vertices with GL_TRIANGLE_STRIP or GL_QUAD_STRIP.

K, but this means a lot of redundant glVertex and glNormal etc, is it still faster than a display list?

Fritz3D

122

February 07, 2002 09:52 PM

*bump*

Myopic Rhino

2,378

February 08, 2002 02:16 AM

quote:Original post by Fritz3D
K, but this means a lot of redundant glVertex and glNormal etc, is it still faster than a display list?

If you''re drawing anything with hard edges (like a cube), you really have no choice but to duplicate some verticies, whether you''re using display lists or vertex arrays.

I''m not really sure what you''re asking, though, because when you''re using vertex arrays, you''re not making calls to glVertex/glNormal at all. The main advantage to vertex arrays is avoiding the overhead of calling those functions repeatedly.

Also, you can place your vertex array code in a display list.