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/**
* \file
* Utility functions for manipulating VBOs.
*/
#pragma once
#include <GL/glew.h>
namespace render
{
namespace detail
{
template<typename Array_T>
GLsizei byteSize(const Array_T& array)
{
return GLsizei(array.size() * sizeof(typename Array_T::value_type));
}
}
/**
* \brief
* Generate a VBO from the given data
*
* \param target
* Binding point for the VBO (e.g. GL_ARRAY_BUFFER).
*
* \param data
* Array of data to copy into the VBO.
*/
template<typename Array_T>
GLuint makeVBOFromArray(GLenum target, const Array_T& data)
{
// Create and bind
GLuint vboID = 0;
glGenBuffers(1, &vboID);
glBindBuffer(target, vboID);
// Copy data
glBufferData(target, detail::byteSize(data), &data.front(), GL_STATIC_DRAW);
// Return the VBO identifier
return vboID;
}
/// Replace VBO data store with given array
template<typename Array_T>
void replaceVBOData(GLenum target, GLuint vboID, const Array_T& data)
{
glBindBuffer(target, vboID);
glBufferSubData(target, 0, detail::byteSize(data), &data.front());
}
/// Delete a VBO and set its identifier to 0
inline void deleteVBO(GLuint& id)
{
if (id == 0) return;
glDeleteBuffers(1, &id);
id = 0;
}
/// Replace VBO data if new data is smaller than or equal to existing data
/**
* \param target
* VBO target (e.g. GL_ARRAY_BUFFER).
*
* \param vboID
* Identifier variable for the VBO. If this is 0 (no VBO allocated), this
* function does nothing. If the new data size is larger than the existing
* data, this VBO is deleted and its identifier reset to 0.
*/
template<typename Array_T>
void replaceVBODataIfPossible(GLenum target, GLuint& vboID,
const Array_T& existingData,
const Array_T& newData)
{
if (vboID != 0)
{
if (newData.size() <= existingData.size())
{
// Replace VBO data
replaceVBOData(GL_ARRAY_BUFFER, vboID, newData);
}
else
{
// Size mismatch, cannot replace data so invalidate VBO
deleteVBO(vboID);
}
}
}
}
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