Hello,
I have fairly large C++ objects which load mesh data into memory and then draws based on an OnDisplay callback.
The problem is that the refresh rate is really slow which I suspect is because my code is poorly written.
Anyway; here is what my class looks like (function prototypes shown to give you an idea of how my class is set up).
What I want to know is if it is possible to just call the “glDrawElements” function somehow on what is in memory if most of my VBOs haven’t changed and skip my Begin and end draw functions as shown below.
Mostly I will just have the camera moving through the scene.
I set these functions up based on tutorials and documentation so I know they work; I just want to speed up the drawing, especially when the meshes I am loading in are 100MB + in size.
Thank you so much for your time and any assistance you can provide.
class MyMeshData
{
public:
MyMeshData();
~MyMeshData();
// Save up data into GPU buffers.
bool Initialize(const MeshDataFromFileClass * StaticMeshData);
// Update vertex positions for deformed meshes.
void UpdateVertexPosition(const MeshDataFromFileClass * StaticMeshData, const MyVector4Class * pVertices) const;
// Bind buffers, set vertex arrays, turn on lighting and texture.
void BeginDraw(ShadingMode pShadingMode) const;
// Draw all the faces with specific material with given shading mode.
void Draw(int pMaterialIndex, ShadingMode pShadingMode) const;
// Unbind buffers, reset vertex arrays, turn off lighting and texture.
void EndDraw() const;
// Get the count of material groups
int GetSubMeshCount() const { return mSubMeshes.GetCount(); }
private:
enum
{
VERTEX_VBO,
NORMAL_VBO,
UV_VBO,
INDEX_VBO,
VBO_COUNT,
};
// For every material, record the offsets in every VBO and triangle counts
struct SubMesh
{
SubMesh() : IndexOffset(0), TriangleCount(0) {}
int IndexOffset;
int TriangleCount;
};
GLuint mVBONames[VBO_COUNT];
MyMeshArray<SubMesh*> mSubMeshes;
bool mHasNormal;
bool mHasUV;
bool mAllByControlPoint; // Save data in VBO by control point or by polygon vertex.
};
And here is my Initialize Function:
bool Initialize(const MeshDataFromFileClass * StaticMeshData) {
[...]
/*
Earlier code that retrieves data from file removed.
Only the point where the data is transferred to the GPU is shown.
*/
// Create VBOs
glGenBuffers(VBO_COUNT, mVBONames);
// Save vertex attributes into GPU
glBindBuffer(GL_ARRAY_BUFFER, mVBONames[VERTEX_VBO]);
glBufferData(GL_ARRAY_BUFFER, lPolygonVertexCount * VERTEX_STRIDE * sizeof(float), lVertices, GL_STATIC_DRAW);
delete [] lVertices;
if (mHasNormal)
{
glBindBuffer(GL_ARRAY_BUFFER, mVBONames[NORMAL_VBO]);
glBufferData(GL_ARRAY_BUFFER, lPolygonVertexCount * NORMAL_STRIDE * sizeof(float), lNormals, GL_STATIC_DRAW);
delete [] lNormals;
}
if (mHasUV)
{
glBindBuffer(GL_ARRAY_BUFFER, mVBONames[UV_VBO]);
glBufferData(GL_ARRAY_BUFFER, lPolygonVertexCount * UV_STRIDE * sizeof(float), lUVs, GL_STATIC_DRAW);
delete [] lUVs;
}
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mVBONames[INDEX_VBO]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, lPolygonCount * TRIANGLE_VERTEX_COUNT * sizeof(unsigned int), lIndices, GL_STATIC_DRAW);
delete [] lIndices;
}
Here is my BeginDraw Function:
void MyMeshData::BeginDraw(ShadingMode pShadingMode) const
{
glBindBuffer(GL_ARRAY_BUFFER, mVBONames[VERTEX_VBO]);
/*
glVertexPointer(VERTEX_STRIDE, GL_FLOAT, 0, 0);
glEnableClientState(GL_VERTEX_ARRAY);
*/
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, VERTEX_STRIDE, GL_FLOAT, GL_FALSE, 0, 0);
// Set normal array.
if (mHasNormal && pShadingMode == SHADING_MODE_SHADED)
{
glBindBuffer(GL_ARRAY_BUFFER, mVBONames[NORMAL_VBO]);
glNormalPointer(GL_FLOAT, 0, 0);
glEnableClientState(GL_NORMAL_ARRAY);
}
// Set UV array.
if (mHasUV && pShadingMode == SHADING_MODE_SHADED)
{
glBindBuffer(GL_ARRAY_BUFFER, mVBONames[UV_VBO]);
glTexCoordPointer(UV_STRIDE, GL_FLOAT, 0, 0);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
}
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mVBONames[INDEX_VBO]);
if (pShadingMode != SHADING_MODE_SHADED)
{
glColor4fv(DEFAULT_WIREFRAME_COLOR);
}
}
My Draw function …
void MyMeshData::Draw(int pMaterialIndex, ShadingMode pShadingMode) const
{
// Where to start.
GLsizei lOffset = mSubMeshes[pMaterialIndex]->IndexOffset * sizeof(unsigned int);
if ( pShadingMode == SHADING_MODE_SHADED)
{
const GLsizei lElementCount = mSubMeshes[pMaterialIndex]->TriangleCount * 3;
glDrawElements(GL_TRIANGLES, lElementCount, GL_UNSIGNED_INT, reinterpret_cast<const GLvoid *>(lOffset));
}
else
{
for (int lIndex = 0; lIndex < mSubMeshes[pMaterialIndex]->TriangleCount; ++lIndex)
{
glDrawElements(GL_LINE_LOOP, TRIANGLE_VERTEX_COUNT, GL_UNSIGNED_INT, reinterpret_cast<const GLvoid *>(lOffset));
lOffset += sizeof(unsigned int) * TRIANGLE_VERTEX_COUNT;
}
}
}
My EndDraw Function …
void VBOMesh::EndDraw() const
{
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}