glMesh.cpp

#include "glMesh.hpp"
#include "glShader.hpp"
#include "../GL3/gl3w.h"

 // Note - these correspond to the AttributeT enum found in UnivMesh.hpp
const char* AttribNames[MatSys::NUM_ATTRIBUTES] =
{
    "inPosition",
    "inColour",
    "inUV",
    "inLUV",
    "inNormal"
};
const int AttribSizes[MatSys::NUM_ATTRIBUTES] =
{
    sizeof(float) * 3,
    sizeof(float) * 4,
    sizeof(float) * 2,
    sizeof(float) * 2,
    sizeof(float) * 3
};
const int AttribOffsets[MatSys::NUM_ATTRIBUTES] =
{
    0,
    sizeof(float) * 4,
    sizeof(float) * 8,
    sizeof(float) * 10,
    sizeof(float) * 12
};

glMeshT::glMeshT(WindingT W)
{
    UnivMeshT::UnivMeshT(W);
    for (int i = 0; i < MatSys::NUM_ATTRIBUTES; i++)
        iVBOs[i] = 0;
    iVAO = 0;
    lastBound = NULL;
}

glMeshT::~glMeshT()
{
    for (int i = 0; i < MatSys::NUM_ATTRIBUTES; i++)
    {
        unsigned int vbo = iVBOs[i];
        if (vbo != 0)
        {
            iVBOs[i] = 0;
            glDeleteBuffers(1, &vbo);
        }
    }
    if (iVAO != 0)
    {
        glDeleteVertexArrays(1, &iVAO);
        iVAO = 0;
    }
}

void glMeshT::Init()
{
    for (int i = 0; i < MatSys::NUM_ATTRIBUTES; i++)
    {
        if (bAttributeNeeded[i])
        {
            unsigned int vbo;
            glGenBuffers(1, &vbo);
            iVBOs[i] = vbo;
        }
    }
    glGenVertexArrays(1, &iVAO);
}

void glMeshT::Update()
{
    if (!bModified) return;
    RebuildVBOs();
    bModified = false;
}

void glMeshT::RebuildVBOs()
{
    unsigned int cnt = GetVertexCount();
    for (int i = 0; i < MatSys::NUM_ATTRIBUTES; i++)
    {
        unsigned int vbo = iVBOs[i];
        if (vbo != 0)
        {
            glBindBuffer(GL_ARRAY_BUFFER, vbo);
            unsigned int len = cnt * AttribSizes[i];
            char* tmp = new char[len];
            int offset = 0;
            for (unsigned int j = 0; j < cnt; j++)
            {
                memcpy(tmp + offset, (&Vertices[j]) + AttribOffsets[i], AttribSizes[i]);
                offset += AttribSizes[i];
            }
            glBufferData(GL_ARRAY_BUFFER, len, tmp, GL_STATIC_DRAW);
            delete [] tmp;
        }
    }
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}

void glMeshT::RebuildVAO(glShaderT* shader)
{
    glBindVertexArray(iVAO);
    for (int i = 0; i < MatSys::NUM_ATTRIBUTES; i++)
    {
        unsigned int vbo = iVBOs[i];
        if (vbo != 0)
        {
            glBindBuffer(GL_ARRAY_BUFFER, vbo);
            shader->BindAttribute(AttribNames[i], AttribSizes[i]);
        }
    }
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    // We don't unbind here - intentional
}

void glMeshT::Render(glShaderT* shader)
{
    if (shader != lastBound)
    {
        RebuildVAO(shader); // This will leave the VAO bound for us
        lastBound = shader;
    }
    else
        glBindVertexArray(iVAO);
    glDrawArrays(GL_TRIANGLES, 0, GetVertexCount());
    glBindVertexArray(0);
}