gamecodebook/Chapter14/VertexArray.cpp

// ----------------------------------------------------------------
// From Game Programming in C++ by Sanjay Madhav
// Copyright (C) 2017 Sanjay Madhav. All rights reserved.
// 
// Released under the BSD License
// See LICENSE in root directory for full details.
// ----------------------------------------------------------------

#include "VertexArray.h"
#include <GL/glew.h>

VertexArray::VertexArray(const void* verts, unsigned int numVerts, Layout layout,
	const unsigned int* indices, unsigned int numIndices)
	:mNumVerts(numVerts)
	,mNumIndices(numIndices)
{
	// Create vertex array
	glGenVertexArrays(1, &mVertexArray);
	glBindVertexArray(mVertexArray);

	unsigned vertexSize = GetVertexSize(layout);

	// Create vertex buffer
	glGenBuffers(1, &mVertexBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, mVertexBuffer);
	glBufferData(GL_ARRAY_BUFFER, numVerts * vertexSize, verts, GL_STATIC_DRAW);

	// Create index buffer
	glGenBuffers(1, &mIndexBuffer);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mIndexBuffer);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, numIndices * sizeof(unsigned int), indices, GL_STATIC_DRAW);

	// Specify the vertex attributes
	if (layout == PosNormTex)
	{
		// Position is 3 floats
		glEnableVertexAttribArray(0);
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, vertexSize, 0);
		// Normal is 3 floats
		glEnableVertexAttribArray(1);
		glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, vertexSize,
			reinterpret_cast<void*>(sizeof(float) * 3));
		// Texture coordinates is 2 floats
		glEnableVertexAttribArray(2);
		glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, vertexSize,
			reinterpret_cast<void*>(sizeof(float) * 6));
	}
	else if (layout == PosNormSkinTex)
	{
		// Position is 3 floats
		glEnableVertexAttribArray(0);
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, vertexSize, 0);
		// Normal is 3 floats
		glEnableVertexAttribArray(1);
		glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, vertexSize,
			reinterpret_cast<void*>(sizeof(float) * 3));
		// Skinning indices (keep as ints)
		glEnableVertexAttribArray(2);
		glVertexAttribIPointer(2, 4, GL_UNSIGNED_BYTE, vertexSize,
			reinterpret_cast<void*>(sizeof(float) * 6));
		// Skinning weights (convert to floats)
		glEnableVertexAttribArray(3);
		glVertexAttribPointer(3, 4, GL_UNSIGNED_BYTE, GL_TRUE, vertexSize,
			reinterpret_cast<void*>(sizeof(float) * 6 + sizeof(char) * 4));
		// Texture coordinates
		glEnableVertexAttribArray(4);
		glVertexAttribPointer(4, 2, GL_FLOAT, GL_FALSE, vertexSize,
			reinterpret_cast<void*>(sizeof(float) * 6 + sizeof(char) * 8));
	}
}

VertexArray::~VertexArray()
{
	glDeleteBuffers(1, &mVertexBuffer);
	glDeleteBuffers(1, &mIndexBuffer);
	glDeleteVertexArrays(1, &mVertexArray);
}

void VertexArray::SetActive()
{
	glBindVertexArray(mVertexArray);
}

unsigned int VertexArray::GetVertexSize(VertexArray::Layout layout)
{
	unsigned vertexSize = 8 * sizeof(float);
	if (layout == PosNormSkinTex)
	{
		vertexSize = 8 * sizeof(float) + 8 * sizeof(char);
	}
	return vertexSize;
}