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#include "mesh.h"
#include "vertex.hpp"
#include <cstddef>
#define offset_ptr(T, m) ((reinterpret_cast<char *>(1)) + offsetof(T, m) - 1)
Mesh::Mesh(const std::span<const Vertex> vertices, const std::span<const unsigned int> indices, GLenum m) :
m_vertexArrayObject {}, m_vertexArrayBuffers {}, m_numIndices {static_cast<GLsizei>(indices.size())}, mode {m}
{
glGenVertexArrays(1, &m_vertexArrayObject);
glBindVertexArray(m_vertexArrayObject);
glGenBuffers(2, m_vertexArrayBuffers.data());
glBindBuffer(GL_ARRAY_BUFFER, m_vertexArrayBuffers[0]);
glBufferData(GL_ARRAY_BUFFER, static_cast<GLsizeiptr>(sizeof(Vertex) * vertices.size()), vertices.data(),
GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), offset_ptr(Vertex, pos));
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), offset_ptr(Vertex, texCoord));
glEnableVertexAttribArray(2);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), offset_ptr(Vertex, normal));
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_vertexArrayBuffers[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, static_cast<GLsizeiptr>(sizeof(indices[0]) * indices.size()), indices.data(),
GL_STATIC_DRAW);
glBindVertexArray(0);
}
Mesh::~Mesh()
{
glDeleteBuffers(NUM_BUFFERS, m_vertexArrayBuffers.data());
glDeleteVertexArrays(1, &m_vertexArrayObject);
}
void
Mesh::Draw() const
{
glBindVertexArray(m_vertexArrayObject);
glDrawElementsBaseVertex(mode, m_numIndices, GL_UNSIGNED_INT, nullptr, 0);
glBindVertexArray(0);
}
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