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OpenGL Few questions on opengl's vertex arrays

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dopeflow    124
1. Is there a limit to how many arrays you can make/use? I have a mesh manager so memory is optimized in a way already, but say I have 100 different mesh type each with its own array that will be fine? 2. Im using md2 for mesh format. So I will need to store each animation frame info into the array as well. Is it possible to pass the beginning index of the frame to glDrawElements (ie if frame 3 begins at index 600 of my array i would pass that and pass m_nbVertices long since all animation have the same vertices count. 3. What does glLockArrays and glUnlockArrays do exactly? is it useful to use them? 4. How do I use multiple array? I mean how to I pass from one array to the other. I did a quick test just now and my computer completely crashed, must have not loaded the array correctly. First mesh to render(terrain) ================================ glLockArraysEXT(0, vertXRes*vertYRes); glVertexPointer(3, GL_FLOAT, 0, posVB); glEnableClientState(GL_VERTEX_ARRAY); glDrawElements.... glUnlockArraysEXT; Second mesh to render ======================== glLockArraysEXT(0, m_numVertices); glVertexPointer(3, GL_FLOAT, 0, posVB); glEnableClientState(GL_VERTEX_ARRAY); glDrawElements(GL_TRIANGLES, m_numVertices, GL_UNSIGNED_INT, posVB); glUnlockArraysEXT; This will help me a lot if I figure these out, thanks in advance!

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Raduprv    997
First, try to use the normal vertex array function, not the compiled vertex array extension, and see if it works.

The size of the array shouldn''t matter, only that, of course, the more vertices, the more tiem to render them.


3. What does glLockArrays and glUnlockArrays do exactly? is it useful to use them?

They might speed up the things a little bit, but you can''t modify the content of those arrays if you do that.

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dopeflow    124
My application currently work if I only use 1 vertex array(ie only render the terrain) but if I try using multiple arrays (1 for the terrain and also render the meshes with an array) it crashes.

Dont need to modify the array ever. They will always be the same.

Thanks for your help, still need some answers though

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dopeflow    124
Alright I dont crash now using glDrawArrays....but holy shit check that out lol

Must be with the ways im building my array....although i think its fine.

Are you sure this is okay, I mean the order in which I call them and all?

glVertexPointer(3, GL_FLOAT, 0, posVB);
glDrawArrays(GL_TRIANGLES, 0, 3*m_numTriangles);

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dopeflow    124
Well thing is im loading my array with the same data I used before to render my mesh vertex per vertex (it works perfect that way), so the data is obviously good.

the data in vertexListPtr is good im certain of it.

posVB= new float[3*m_numVertices];

for(int i= 0; i < m_numVertices; i++)
posVB[3*i+0]= vertexListPtr[i ].x;
posVB[3*i+1]= vertexListPtr[i ].y;
posVB[3*i+2]= vertexListPtr[i ].z;

edit by ze: fixed code. Please people, don't use i as a loop counter when posting code.

[edited by - zealouselixir on April 30, 2003 12:02:17 AM]

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Guest Anonymous Poster   
Guest Anonymous Poster
You put posVB as the "elements" pointer. That''s wrong. That should be a number of indices.

DrawArrays is slow, because you get no vertex cache re-use on modern cards.

LockArrays() does two things:
1) tells the driver how many vertices there will be in the array (i e, what the maximum index value will be) -- very useful for HT&L cards
2) tells the driver that it can cache transformed vertices until you unlock, unless you re-specify arrays with new calls to VertexPointer (very useful for software transform cards doing multipass)

DrawRangeElements does 1), but not 2).

As far as GL is concerned, there is only one logical vertex array, starting wherever you put the VertexPointer (and NormalPointer, and TexCoordPointer, etc). When you re-specify some other base address, that''s now "the" vertex array. Thus, you can have as many as you can malloc(); GL doesn''t care.

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dopeflow    124

You put posVB as the "elements" pointer. That''s wrong. That should be a number of indices.

so you mean when I do
glVertexPointer(3, GL_FLOAT, 0, posVB);

I shouldnt pass posVB? this doesnt makes sense to me, just looked at msdn and it says that third parameter of glVertexPointer should be a pointer to the first element of my array, which is exactly what im doing.

Unless you mean something else?

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