VBO not faster than immediate mode?

Subject: VBO not faster than immediate mode?

Date: Fri, 23 May 2008 19:34:43 +0300

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Hello,

I am learning OpenGL and building a simple particle demo with velocity, friction, forces, etc.

I started with immediate mode and drew each particle with glVertex() and it went up to 200k particles with about 50fps (2.4Ghz iMac & ati 2600 pro & no vsync).

Then I learned about VBO's and how much faster they're supposed to be. I modified my code to use VBO instead but the speed difference is only about 10% more compared to glBegin/end() with zillion individual glColor() glVertex() pairs ?!?

I am using 4 threads to calculate the math and timer to render the scene. Is there anything to speed up things or is GLSL -> FBO -> VBO only possible solution? (well, frankly that is my next goal and questions anyway).

But for now; Is it possible that there is something wrong in my VBO usage or can driver somehow optimize the glVertex() calls and thus no huge gains visible?

Thank You.

Here's how I do it:

// build VBO's once

bool buildVBO(int vertexCount,float* pVerArray,float* pColArray )

{

if (pVerArray && pColArray) {

glGenBuffersARB( 1, &m_nVBOVertices );

glBindBufferARB( GL_ARRAY_BUFFER_ARB, m_nVBOVertices );

glBufferDataARB( GL_ARRAY_BUFFER_ARB, vertexCount * 3 * sizeof(GLfloat),pVerArray, GL_DYNAMIC_DRAW );

glGenBuffersARB( 1, &m_nVBOColors );

glBindBufferARB( GL_ARRAY_BUFFER_ARB, m_nVBOColors );

glBufferDataARB( GL_ARRAY_BUFFER_ARB, vertexCount * 3 * sizeof(GLfloat), pColArray, GL_DYNAMIC_DRAW );

if (m_nVBOVertices && m_nVBOColors) return true;

}

return false;

}

// update new vertex-data

void refreshData(int vertexCount,float* pVerArray,float* pColArray )

{

glBindBufferARB(GL_ARRAY_BUFFER_ARB, m_nVBOVertices);

glBufferDataARB(GL_ARRAY_BUFFER_ARB, vertexCount * 3 * sizeof(GLfloat), pVerArray, GL_DYNAMIC_DRAW );

glBindBufferARB(GL_ARRAY_BUFFER_ARB, m_nVBOColors);

glBufferDataARB(GL_ARRAY_BUFFER_ARB, vertexCount * 3 * sizeof(GLfloat), pColArray, GL_DYNAMIC_DRAW );

}

// draw VBO's

void drawVbo(int vertexCount)

{

glEnableClientState( GL_VERTEX_ARRAY );

glEnableClientState( GL_COLOR_ARRAY );

glBindBufferARB( GL_ARRAY_BUFFER_ARB, m_nVBOVertices );

glVertexPointer( 3, GL_FLOAT, 0, 0 );

glBindBufferARB( GL_ARRAY_BUFFER_ARB, m_nVBOColors );

glColorPointer( 3, GL_FLOAT, 0, 0 );

// Render

glDrawArrays( GL_POINTS, 0, vertexCount );

glDisableClientState( GL_COLOR_ARRAY );

glDisableClientState( GL_VERTEX_ARRAY );

}

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