light/Engine/src/Platform/GraphicsAPI/OpenGL/glVertexLayout.cpp

#include "glVertexLayout.h"

#include "glBuffers.h"

#include <glad/glad.h>

namespace Light {

	glVertexLayout::glVertexLayout(Ref<VertexBuffer> buffer, const std::vector<std::pair<std::string, VertexElementType>>& elements)
		: m_ArrayID(NULL)
	{
		// check
		LT_ENGINE_ASSERT(std::dynamic_pointer_cast<glVertexBuffer>(buffer), "glVertexLayout::glVertexLayout: failed to cast 'VertexBuffer' to 'glVertexBuffer'");
		LT_ENGINE_ASSERT(!elements.empty(), "glVertexLayout::glVertexLayout: 'elements' is empty");

		// local
		std::vector<glVertexElementDesc> elementsDesc;
		elementsDesc.reserve(elements.size());
		unsigned int stride = 0u;

		// extract elements desc
		for(const auto& element : elements)
		{
			elementsDesc.push_back(GetElementDesc(element.second, stride));
			stride += elementsDesc.back().typeSize * elementsDesc.back().count;
		}

		// create vertex array
		glCreateVertexArrays(1, &m_ArrayID);

		// bind buffer and array
		buffer->Bind();
		Bind();

		// enable vertex attributes
		unsigned int index = 0u;
		for (const auto& elementDesc : elementsDesc)
		{
			glVertexAttribPointer(index, elementDesc.count, elementDesc.type, GL_FALSE, stride, (const void*)elementDesc.offset);
			glEnableVertexAttribArray(index++);
		}
	}

	glVertexLayout::~glVertexLayout()
	{
		glDeleteVertexArrays(1, &m_ArrayID);
	}

	void glVertexLayout::Bind()
	{
		glBindVertexArray(m_ArrayID);
	}

	void glVertexLayout::UnBind()
	{
		glBindVertexArray(NULL);
	}

	glVertexElementDesc glVertexLayout::GetElementDesc(VertexElementType type, unsigned int offset)
	{
		switch (type)
		{
		/* byte */
		case Light::VertexElementType::Byte1: return { GL_BYTE, 1u, sizeof(GLbyte), offset };
		case Light::VertexElementType::Byte2: return { GL_BYTE, 1u, sizeof(GLbyte), offset };
		case Light::VertexElementType::Byte4: return { GL_BYTE, 1u, sizeof(GLbyte), offset };

		/* ubyte */
		case Light::VertexElementType::UByte1: return { GL_UNSIGNED_BYTE, 1u, sizeof(GLubyte), offset };
		case Light::VertexElementType::UByte2: return { GL_UNSIGNED_BYTE, 2u, sizeof(GLubyte), offset };
		case Light::VertexElementType::UByte4: return { GL_UNSIGNED_BYTE, 4u, sizeof(GLubyte), offset };

		/* int */
		case VertexElementType::Int1: return { GL_INT, 1u, sizeof(GLint), offset };
		case VertexElementType::Int2: return { GL_INT, 2u, sizeof(GLint), offset };
		case VertexElementType::Int3: return { GL_INT, 3u, sizeof(GLint), offset };
		case VertexElementType::Int4: return { GL_INT, 4u, sizeof(GLint), offset };

		/* uint */
		case VertexElementType::UInt1: return { GL_UNSIGNED_INT, 1u, sizeof(GLuint), offset };
		case VertexElementType::UInt2: return { GL_UNSIGNED_INT, 2u, sizeof(GLuint), offset };
		case VertexElementType::UInt3: return { GL_UNSIGNED_INT, 3u, sizeof(GLuint), offset };
		case VertexElementType::UInt4: return { GL_UNSIGNED_INT, 4u, sizeof(GLuint), offset };

		/* float */
		case VertexElementType::Float1: return { GL_FLOAT, 1u, sizeof(GLfloat), offset };
		case VertexElementType::Float2: return { GL_FLOAT, 2u, sizeof(GLfloat), offset };
		case VertexElementType::Float3: return { GL_FLOAT, 3u, sizeof(GLfloat), offset };
		case VertexElementType::Float4: return { GL_FLOAT, 4u, sizeof(GLfloat), offset };

		default:
			LT_ENGINE_ASSERT(false, "glVertexLayout::GetElementDesc: invalid 'VertexElementType'");
			return {};
		}
	}

}