Render indexed data from Q3 BSP

228

Author

February 27, 2015 02:42 PM

Hi

I'm trying to render a Quake 3 BSP file using core OpenGL. I have the file loaded ok ( using the same code from a old OpenGL program ) - but I can't work out how to translate the old way of glDrawElements into the new core way of drawing indexed arrays.

this is what I end up with - a scrambled mess

So, once the BSP is loaded - I upload all the data to the GPU like this:


//-----------------------------------------------------------------------------
//
// Upload vertex arrays to GPU
bool bsp_uploadBspToGPU()
//-----------------------------------------------------------------------------
{
    //
    // Store model and all meshes in one VAO
    glGenVertexArrays(1, &bspVAO_ID);
    glBindVertexArray(bspVAO_ID);

//    GL_CHECK(glGenBuffers(1, &elementArrayID));
//    GL_CHECK(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
//    GL_CHECK(glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(m_numOfMeshIndexes * sizeof(int)), &m_pMeshIndex, GL_STATIC_DRAW));

    //
    // Load vertices into GPU
    GL_CHECK(glGenBuffers(1, &bspVBO_VERT));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));
//    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(tBSPVertex), &(m_pVerts[0].vPosition), GL_STATIC_DRAW));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(glm::vec3), &(m_pVerts[0].vPosition), GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, 0));
    //
    // Load texture coordinates into GPU
    GL_CHECK(glGenBuffers(1, &bspVBO_TEXCOORD));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_TEXCOORD));
//    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(tBSPVertex), &(m_pVerts[0].vTextureCoord), GL_STATIC_DRAW));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(glm::vec2), &(m_pVerts[0].vTextureCoord), GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, 0));

    //
    // Load lightmap coordinates into GPU
    GL_CHECK(glGenBuffers(1, &bspVBO_LIGHTMAP));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_LIGHTMAP));
//    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(tBSPVertex), &(m_pVerts[0].vLightmapCoord), GL_STATIC_DRAW));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(glm::vec2), &(m_pVerts[0].vLightmapCoord), GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, 0));

    //
    // Load normals into GPU
    GL_CHECK(glGenBuffers(1, &bspVBO_NORMALS));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_NORMALS));
//    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(tBSPVertex), &(m_pVerts[0].vNormal), GL_STATIC_DRAW));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(glm::vec3), &(m_pVerts[0].vNormal), GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, 0));

    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

and after walking the BSP and finding all the viewable faces which I store in an array for later sorting, I then render each face like this:



//-----------------------------------------------------------------------------
//
// Actually draw the BSP face
void bsp_drawFace(tBSPFace *ptrFace)
//-----------------------------------------------------------------------------
{
    GL_ASSERT(glBindVertexArray(bspVAO_ID));

    GL_ASSERT(glUseProgram(shaderProgram[SHADER_GEOMETRY_PASS].programID));

    wrapglBindTexture(GL_TEXTURE0, texturesLoaded[TEX_WALL].texID);
    GL_ASSERT(glUniform1i(shaderProgram[SHADER_GEOMETRY_PASS].inTextureUnit, 0));

    GL_ASSERT(glUniformMatrix4fv(glGetUniformLocation(shaderProgram[SHADER_GEOMETRY_PASS].programID, "u_modelMat"), 1, false, glm::value_ptr(modelMatrix) ));

//    GL_ASSERT(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
//    GL_ASSERT(glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(int) * m_numOfMeshIndexes, &m_pMeshIndex[0], GL_STATIC_DRAW));

    GL_ASSERT(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[SHADER_GEOMETRY_PASS].inVertsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[SHADER_GEOMETRY_PASS].inVertsID, 3, GL_FLOAT, GL_FALSE, 0, NULL));

    GL_ASSERT(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_TEXCOORD));
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[SHADER_GEOMETRY_PASS].inTextureCoordsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[SHADER_GEOMETRY_PASS].inTextureCoordsID, 2, GL_FLOAT, GL_FALSE, 0, NULL));

    GL_ASSERT(glDrawElements(GL_TRIANGLES, ptrFace->numOfVerts, GL_UNSIGNED_INT, &m_pMeshIndex[ptrFace->startVertIndex]));

//    GL_ASSERT(glDrawElements(GL_TRIANGLES, ptrFace->numMeshVerts, GL_UNSIGNED_INT, &m_pMeshIndex[ptrFace->meshVertIndex]));


    printf("Num verts in this face [ %i ] \n", ptrFace->numOfVerts);

    for (int i = 0; i != ptrFace->numOfVerts; i++)
    {
        printf("Index [ %i ] - [ %i ]\n", i, m_pMeshIndex[ptrFace->startVertIndex + i]);

    }

}

The data appears to be correct, ptrFace->numOfVerts seems to be the right number, and the indexes printed out seem correct as well.


<snip>

Num verts in this face [ 8 ] 
Index [ 0 ] - [ 0 ]
Index [ 1 ] - [ 2 ]
Index [ 2 ] - [ 4 ]
Index [ 3 ] - [ 0 ]
Index [ 4 ] - [ 1 ]
Index [ 5 ] - [ 2 ]
Index [ 6 ] - [ 2 ]
Index [ 7 ] - [ 6 ]

Num verts in this face [ 4 ] 
Index [ 0 ] - [ 4 ]
Index [ 1 ] - [ 0 ]
Index [ 2 ] - [ 4 ]
Index [ 3 ] - [ 5 ]

</snip>

I have also read that when using glDrawElements that you can use an indexed buffer as well, but I couldn't get that working either.

Any pointers on getting glDrawElements working correctly?

Thanks

Sponji

2,505

February 27, 2015 03:37 PM

Seems like the problem is that your vertex data is interleaved and you're using them as if they were in their own arrays. You could create a single buffer and upload all vertex data in it, then use glVertexAttribPointer for each attribute and pass the offset in bytes for the last parameter. Also, the stride should be the size of the vertex.


// offset for position is 0
glEnableVertexAttribArray(position_index);
glVertexAttribPointer(position_index, 3, GL_FLOAT, GL_FALSE, sizeof(YourVertex), (void*)(0));

// offset for normal is the size of position which would be 3 floats
glEnableVertexAttribArray(position_index);
glVertexAttribPointer(normal_index, 3, GL_FLOAT, GL_FALSE, sizeof(YourVertex), (void*)(sizeof(float) * 3));

// ... and the offset for the next attribute would be sizeof(float) * (3 + 3)

And about index buffers, just use GL_ELEMENT_ARRAY_BUFFER, send the data and then call glDrawElements with 0 as the last parameter (which is the offset).

Derp

Droid_999

228

Author

February 27, 2015 09:38 PM

Seems like the problem is that your vertex data is interleaved and you're using them as if they were in their own arrays. You could create a single buffer and upload all vertex data in it, then use glVertexAttribPointer for each attribute and pass the offset in bytes for the last parameter. Also, the stride should be the size of the vertex.
// offset for position is 0
glEnableVertexAttribArray(position_index);
glVertexAttribPointer(position_index, 3, GL_FLOAT, GL_FALSE, sizeof(YourVertex), (void*)(0));

// offset for normal is the size of position which would be 3 floats
glEnableVertexAttribArray(position_index);
glVertexAttribPointer(normal_index, 3, GL_FLOAT, GL_FALSE, sizeof(YourVertex), (void*)(sizeof(float) * 3));

// ... and the offset for the next attribute would be sizeof(float) * (3 + 3)
And about index buffers, just use GL_ELEMENT_ARRAY_BUFFER, send the data and then call glDrawElements with 0 as the last parameter (which is the offset).

Ok - like this?


//-----------------------------------------------------------------------------
//
// Upload vertex arrays to GPU
bool bsp_uploadBspToGPU()
//-----------------------------------------------------------------------------
{
    //
    // Store model and all meshes in one VAO
    glGenVertexArrays(1, &bspVAO_ID);
    glBindVertexArray(bspVAO_ID);

    GL_CHECK(glGenBuffers(1, &elementArrayID));
    GL_CHECK(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
    GL_CHECK(glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(m_numOfMeshIndexes * sizeof(int)), &m_pMeshIndex, GL_STATIC_DRAW));
    //
    // Load vertices information into GPU
    GL_CHECK(glGenBuffers(1, &bspVBO_VERT));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(tBSPVertex), &m_pVerts[0].vPosition, GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, 0));

    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

and then render like this?


//-----------------------------------------------------------------------------
//
// Actually draw the BSP face
void bsp_drawFace(tBSPFace *ptrFace)
//-----------------------------------------------------------------------------
{
    GL_ASSERT(glBindVertexArray(bspVAO_ID));

    GL_ASSERT(glUseProgram(shaderProgram[SHADER_GEOMETRY_PASS].programID));

    wrapglBindTexture(GL_TEXTURE0, texturesLoaded[TEX_WALL].texID);
    GL_ASSERT(glUniform1i(shaderProgram[SHADER_GEOMETRY_PASS].inTextureUnit, 0));

    GL_ASSERT(glUniformMatrix4fv(glGetUniformLocation(shaderProgram[SHADER_GEOMETRY_PASS].programID, "u_modelMat"), 1, false, glm::value_ptr(modelMatrix) ));

    GL_ASSERT(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
    GL_ASSERT(glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(int) * m_numOfMeshIndexes, &m_pMeshIndex[0], GL_STATIC_DRAW));

    GL_ASSERT(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));

    // Position
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[SHADER_GEOMETRY_PASS].inVertsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[SHADER_GEOMETRY_PASS].inVertsID, 3, GL_FLOAT, GL_FALSE, sizeof(tBSPVertex), (void*)(0)));

    // Texture coords
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[SHADER_GEOMETRY_PASS].inTextureCoordsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[SHADER_GEOMETRY_PASS].inTextureCoordsID, 2, GL_FLOAT, GL_FALSE, sizeof(tBSPVertex), (void*)(sizeof(float) * 3)));

    // Lightmap coords
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[SHADER_GEOMETRY_PASS].inTextureCoordsID_1));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[SHADER_GEOMETRY_PASS].inTextureCoordsID_1, 2, GL_FLOAT, GL_FALSE, sizeof(tBSPVertex), (void*)(sizeof(float) * 3) + (sizeof(float) * 2)));

    // Normals
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[SHADER_GEOMETRY_PASS].inNormalsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[SHADER_GEOMETRY_PASS].inNormalsID, 3, GL_FLOAT, GL_FALSE, sizeof(tBSPVertex), (void*)(sizeof(float) * 3) + (sizeof(float) * 4)));

    GL_ASSERT(glDrawElements(GL_TRIANGLES, ptrFace->numOfVerts, GL_UNSIGNED_INT, ptrFace->startVertIndex));

//    GL_ASSERT(glDrawElements(GL_TRIANGLES, ptrFace->numMeshVerts, GL_UNSIGNED_INT, &m_pMeshIndex[ptrFace->meshVertIndex]));

}

with tBSPVertex looking like this - I'm ignoring the colors for the moment


struct tBSPVertex
{
    glm::vec3 vPosition;			// (x, y, z) position.
    glm::vec2 vTextureCoord;		// (u, v) texture coordinate
    glm::vec2 vLightmapCoord;	    // (u, v) lightmap coordinate
    glm::vec3 vNormal;			    // (x, y, z) normal vector
    byte color[4];				    // RGBA color for the vertex
};

Won't the last parameter to glDrawElements need to be the index into the tBSPVertex array? If it's 0, then won't it always be drawing just the first triangle?

Thanks

Sponji

2,505

February 28, 2015 10:03 AM

Yeah, looks much better. And you're right about that last parameter, no idea what I was thinking.

Derp

Droid_999

228

Author

February 28, 2015 06:38 PM

Thanks - still nothing on the screen

If I am using an ELEMENT_ARRAY_BUFFER like so:

m_pMeshIndex is an int array read in from the BSP file.


    GL_ASSERT(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
    GL_CHECK(glBufferData(GL_ELEMENT_ARRAY_BUFFER, m_numOfMeshIndexes * sizeof(int), &m_pMeshIndex[0], GL_STATIC_DRAW));

Do I still need to reference the array holding the mesh indexes - like so??


    GL_ASSERT(glDrawElements(GL_TRIANGLES, ptrFace->numOfVerts, GL_UNSIGNED_INT, &m_pMeshIndex[ptrFace->startVertIndex]));

Or should I draw like this because glDrawElement will look up the index??


    GL_ASSERT(glDrawElements(GL_TRIANGLES, ptrFace->numOfVerts, GL_UNSIGNED_INT, ptrFace->startVertIndex));

Cheers

Sponji

2,505

February 28, 2015 08:00 PM

The last one should be correct when you're using buffers, the data is already sent to the GPU and it just tells the offset. I'm not really sure, but I think you have to multiply it by the size of unsigned int though?

Derp

Droid_999

228

Author

March 01, 2015 06:02 PM

Hi

I found this doc describing the quake 3 specs, and a suggestion on how to render the faces:


const Face& curFace = face[visibleFace[f]];
static const stride = sizeof(Vertex); // BSP Vertex, not float[3]
const int offset    = face.firstVertex;

glVertexPointer(3, GL_FLOAT, stride, &(vertex[offset].position));

glClientActiveTextureARB(GL_TEXTURE0_ARB);
glTexCoordPointer(2, GL_FLOAT, stride, &(vertex[offset].textureCoord));

glClientActiveTextureARB(GL_TEXTURE1_ARB);
glTexCoordPointer(2, GL_FLOAT, stride, &(vertex[offset].lightmapCoord));

glDrawElements(GL_TRIANGLES, curFace.meshVertexesCount,
   GL_UNSIGNED_INT, &meshVertex[curFace.firstMeshVertex]);

This is using non-core GL.

How do I replicate that using modern core GL ??

At the moment I have this:


//-----------------------------------------------------------------------------
//
// Actually draw the BSP face
void bsp_drawFace(tBSPFace *ptrFace, int whichShader)
//-----------------------------------------------------------------------------
{
    int stride = sizeof(tBSPVertex); // BSP Vertex, not float[3]

//    GL_ASSERT(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
//    GL_CHECK(glBufferData(GL_ELEMENT_ARRAY_BUFFER, m_numOfMeshIndexes * sizeof(int), &m_pMeshIndex, GL_STATIC_DRAW));

//    GL_ASSERT(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));

    // Position
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inVertsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inVertsID, 3, GL_FLOAT, false, stride, BUFFER_OFFSET(0)));

    // Texture coords
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inTextureCoordsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inTextureCoordsID, 2, GL_FLOAT, false, stride, (void*)(sizeof(glm::vec3))));

    // Lightmap coords
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inTextureCoordsID_1));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inTextureCoordsID_1, 2, GL_FLOAT, false, stride, (void*)sizeof(glm::vec3) + sizeof(glm::vec2)));

    // Normals
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inNormalsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inNormalsID, 3, GL_FLOAT, false, stride, (void*)sizeof(glm::vec3) + (sizeof(glm::vec2) * 4)));

    glDrawElements(GL_TRIANGLES, ptrFace->numMeshVerts, GL_UNSIGNED_INT, &m_pMeshIndex[ptrFace->meshVertIndex]);

    bsp_debugBSPData(ptrFace);
}

I have also tried rendering using an ELEMENT_BUFFER, but I don't get anything on the screen, at the moment, I get flashing red triangles, seemingly centred at 0,0,0.

I can debug a face using this - with double indexes it seems:


// Display BSP data
void bsp_debugBSPData(tBSPFace *ptrFace)
//-----------------------------------------------------------------------------
{
    static bool debugDone = false;

    if (false == debugDone)
    {
        con_print(CON_INFO, true, "Num verts mesh verts [ %i ] Num, Triangles [ %i ]", ptrFace->numMeshVerts, ptrFace->numMeshVerts / 3);

        for (int i = 0; i != ptrFace->numMeshVerts; i++)
        {
            con_print(CON_INFO, true, "Face meshVertIndex [ %i ] meshVertIndex [ %i ]", ptrFace->meshVertIndex + i, m_pMeshIndex[ptrFace->meshVertIndex + i]);
            con_print(CON_INFO, true, "VertexPos [ %i ] [ %3.3f %3.3f %3.3f ]", m_pMeshIndex[ptrFace->meshVertIndex + i],
                      m_pVerts[m_pMeshIndex[ptrFace->meshVertIndex + i]].vPosition.x,
                      m_pVerts[m_pMeshIndex[ptrFace->meshVertIndex + i]].vPosition.y,
                      m_pVerts[m_pMeshIndex[ptrFace->meshVertIndex + i]].vPosition.z );
        }
        debugDone = true;
    }
}

Is it even possible to replicate the above non-core code using modern GL ??

Thanks

Sponji

2,505

March 01, 2015 07:14 PM

Hmm, I'm not really sure about this, but I think you can use glDrawElementsBaseVertex instead of glDrawElements to do it like the example shows, just pass face.firstVertex in the last parameter? Btw, the last multiplication in normal attribute's offset seems to be wrong.

Derp

Droid_999

228

Author

March 02, 2015 02:42 PM

I can now render the BSP data - but only by uploading a face at a time each frame - not the best !!

Here's the routine - it's split into two, the first #define does it the slow way, by pulling out the vertex information for that frame, and uploading to the card. This works ok. The second part should be using the information that is loaded onto the card once at load time - but it doesn't render anything.



//-----------------------------------------------------------------------------
//
// Actually draw the BSP face
void bsp_drawFace(tBSPFace *ptrFace, int whichShader)
//-----------------------------------------------------------------------------
{
//    #define SLOW_WAY

    #ifdef SLOW_WAY
    typedef struct
    {
        glm::vec3   position;
        glm::vec2   texCoords;
        glm::vec3   normals;
    } _myVertex;

    _myVertex myVertex[40];

    int         indexes[40];
    int         i = 0;
    GLuint      vao;
    GLuint      vbo_ID;

    int stride = sizeof(_myVertex);

    for (i = 0; i != ptrFace->numMeshVerts; i++)
    {
        indexes[i] = m_pMeshIndex[ptrFace->startMeshVertIndex + i];

        myVertex[i].position =  m_pVerts[ptrFace->startVertIndex + indexes[i]].vPosition;
        myVertex[i].texCoords = m_pVerts[ptrFace->startVertIndex + indexes[i]].vTextureCoord;
        myVertex[i].normals =   m_pVerts[ptrFace->startVertIndex + indexes[i]].vNormal;
    }

   // create the VAO
    GL_ASSERT(glGenVertexArrays(1, &vao));
    GL_CHECK(glBindVertexArray(vao));
    //
    // create buffers for our vertex data
    GL_ASSERT(glGenBuffers(1, &vbo_ID));

    GL_CHECK(glUseProgram(shaderProgram[whichShader].programID));

    GL_ASSERT(glBindBuffer(GL_ARRAY_BUFFER, vbo_ID));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, ptrFace->numMeshVerts * sizeof(_myVertex), myVertex, GL_STATIC_DRAW));
    //
    // position
    GL_CHECK(glEnableVertexAttribArray(shaderProgram[whichShader].inVertsID));
    GL_CHECK(glVertexAttribPointer(shaderProgram[whichShader].inVertsID,3, GL_FLOAT,GL_FALSE, stride, offsetof(_myVertex, position) ));
    //
    // Textur coordinates
    glEnableVertexAttribArray(shaderProgram[whichShader].inTextureCoordsID);
    glVertexAttribPointer(shaderProgram[whichShader].inTextureCoordsID, 2, GL_FLOAT, false, stride, offsetof(_myVertex, texCoords));
    //
    // Normals
    glEnableVertexAttribArray(shaderProgram[whichShader].inNormalsID);
    glVertexAttribPointer(shaderProgram[whichShader].inNormalsID, 3, GL_FLOAT, false, stride, offsetof(_myVertex, normals));
    //
    // unbind the VAO
    glBindVertexArray(0);

//
// -------------
//


    GL_CHECK(glUniformMatrix4fv(shaderProgram[whichShader].modelMat, 1, false, glm::value_ptr(modelMatrix)));
    GL_CHECK(glUniformMatrix4fv(shaderProgram[whichShader].viewProjectionMat, 1, false, glm::value_ptr(projMatrix * viewMatrix)));

    GL_CHECK(glBindVertexArray(vao));
    //
    // Enable attribute to hold vertex information
    GL_CHECK(glEnableVertexAttribArray(shaderProgram[whichShader].inVertsID));
    GL_CHECK(glEnableVertexAttribArray(shaderProgram[whichShader].inTextureCoordsID));
    GL_CHECK(glEnableVertexAttribArray(shaderProgram[whichShader].inNormalsID));

//    GL_CHECK(glDrawElements(GL_TRIANGLES, ptrFace->numMeshVerts, GL_UNSIGNED_INT, 0));

    glDrawArrays(GL_TRIANGLES, 0, ptrFace->numMeshVerts);

    glUseProgram(0);
    glBindVertexArray(0);

    #else if

    int stride = sizeof(tBSPVertex); // BSP Vertex, not float[3]

    GL_CHECK(glUseProgram(shaderProgram[whichShader].programID));

    GL_CHECK(glBindVertexArray(bspVAO_ID));

    GL_CHECK(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));

    // Position
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inVertsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inVertsID, 3, GL_FLOAT, false, stride, (offsetof(tBSPVertex, vPosition))));

    // Texture coords
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inTextureCoordsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inTextureCoordsID, 2, GL_FLOAT, false, stride, offsetof(tBSPVertex, vTextureCoord)));

    // Lightmap coords - not used in shader yet
//    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inTextureCoordsID_1));
//    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inTextureCoordsID_1, 2, GL_FLOAT, false, stride, offsetof(tBSPVertex, vLightmapCoord)));

    // Normals
    GL_ASSERT(glEnableVertexAttribArray(shaderProgram[whichShader].inNormalsID));
    GL_ASSERT(glVertexAttribPointer(shaderProgram[whichShader].inNormalsID, 3, GL_FLOAT, false, stride, offsetof(tBSPVertex, vNormal)));

    GL_CHECK(glUniformMatrix4fv(shaderProgram[whichShader].modelMat, 1, false, glm::value_ptr(modelMatrix)));
    GL_CHECK(glUniformMatrix4fv(shaderProgram[whichShader].viewProjectionMat, 1, false, glm::value_ptr(projMatrix * viewMatrix)));

    GL_ASSERT(glDrawElementsBaseVertex(GL_TRIANGLES, ptrFace->numMeshVerts, GL_UNSIGNED_INT, (const GLvoid *)ptrFace->startMeshVertIndex, ptrFace->startVertIndex));

    glBindBuffer(GL_ARRAY_BUFFER, 0);

    gl_getAllGLErrors(glGetError(), __FILE__, __LINE__);

    #endif
}

Here's where it's uploaded at load time



//-----------------------------------------------------------------------------
//
// Upload vertex arrays to GPU
bool bsp_uploadBspToGPU()
//-----------------------------------------------------------------------------
{
    //
    // Store model and all meshes in one VAO
    GL_CHECK(glGenVertexArrays(1, &bspVAO_ID));
    GL_CHECK(glBindVertexArray(bspVAO_ID));

    GL_CHECK(glGenBuffers(1, &elementArrayID));
    GL_CHECK(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementArrayID));
    GL_CHECK(glBufferData(GL_ELEMENT_ARRAY_BUFFER, m_numOfMeshIndexes * sizeof(int), &m_pMeshIndex, GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0));
    //
    // Load vertices information into GPU
    GL_CHECK(glGenBuffers(1, &bspVBO_VERT));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, bspVBO_VERT));
    GL_CHECK(glBufferData(GL_ARRAY_BUFFER, m_numOfVerts * sizeof(tBSPVertex), &m_pVerts, GL_STATIC_DRAW));
    GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, 0));

    GL_CHECK(glBindBuffer(GL_VERTEX_ARRAY, 0));
}

Can anyone see why the second way ( using glDrawElementsBaseVertex ) wouldn't work.

Thanks.

Render indexed data from Q3 BSP

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