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DrawElements

Started by Oniera Sep 30, 2001 at 12:23 PM 1 replies 550+ views

Original Post

Sep 30, 2001 at 12:23 PM

I seem to be confused about something... In the command: glVertexPointer(3,GL_FLOAT,0,vertexbuffer); the second variable can be set as GL_FLOAT, but in the actual drawing command: glDrawElements() , you''re third variable has to be a type as either GL_UNSIGNED_BYTE, GL_UNSIGNED_SHORT, or GL_UNSIGNED_INT. Well, If I''m allowed to define my data as GL_FLOAT, why can''t I use GL_FLOAT as my type in the glDrawElements command? Demetrios Georgeadis Director/Programmer Oniera Software Artists

www.oniera.com

LousyPhreak

Jun 5, 2002 at 4:19 PM

the GL_FLOAT in the glVertexPointer references the type of vertex data:

  
struct vertex3d
{
	float x,y,z;
};

vertex3d vertexbuffer[100];

glVertexPointer(3,GL_FLOAT,0,vertexbuffer);

means you got 100 vertices which you can index of type 3*float

then when you use glDrawElements() you specify the type if the INDEX array:

  
unsigned int indices={1,2,3,5,3,1};//remember these are 6 entrys (for next call)

glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,indices);

means you draw 2 (6 elements| 3/tri) triangles (GL_TRIANGLES) and the indices array is of type unsigned int (you can also use ints if your indices arent greater than ~2bil

)

mfg Phreak

--
"Input... need input!" - Johnny Five, Short Circuit.

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