charcoal/OpenGLEngine/SpriteBatch.h

#pragma once

#include "Poseable2D.h"
#include "TextureRenderable.h"
#include "Poseable2DBatch.h"

namespace charcoal
{
	namespace builtin
	{
		template <typename VertexType, typename IndexType>
		class SpriteBatch : public Poseable2DBatch<VertexType, IndexType, TextureRenderable<VertexType, IndexType> >
		{
			// Note: This is VERY similar to builtin::textured::Batch
			// TODO: Use Poseable2D for each sprite's position
			// TODO: Have a texture
			// Note: Uses GL_TEXTURE0. The uniform for this texture should be set in the scene before rendering.
			SpriteBatch(
				TextureRenderable<VertexType, IndexType>* renderable,
				int element_count
			) : Poseable2DBatch<VertexType, IndexType, TextureRenderable<VertexType, IndexType> >(renderable, element_count)
			{}

			SpriteBatch(
				TextureRenderable<VertexType, IndexType>* renderable,
				int element_count,
				int element_render_count
			) : Poseable2DBatch<VertexType, IndexType, TextureRenderable<VertexType, IndexType> >(renderable, element_count, element_render_count)
			{}

			void preprender() const override
			{
				// Note: Uses GL_TEXTURE0. The uniform for this texture should be set in the scene.
				glActiveTexture(GL_TEXTURE0);
				glBindTexture(GL_TEXTURE_2D, charcoal::Batch<VertexType, IndexType, 1, TextureRenderable<VertexType, IndexType> >::m_p_renderable->get_texture()->get_texture());
				glBindSampler(0, charcoal::Batch<VertexType, IndexType, 1, TextureRenderable<VertexType, IndexType> >::m_p_renderable->get_sampler()->get_sampler());
			}

		protected:
			void setup_vao() override
			{
				glBindBuffer(GL_ARRAY_BUFFER, charcoal::Batch<VertexType, IndexType, 1, TextureRenderable<VertexType, IndexType> >::m_vertex_vbo);
				glEnableVertexAttribArray(0);
				glEnableVertexAttribArray(1);
				// TODO: Figure out how to do this without offsetof :(
				glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(VertexType), (void*)offsetof(VertexType, position));
				glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(VertexType), (void*)offsetof(VertexType, uv));
				glBindBuffer(GL_ARRAY_BUFFER, charcoal::Batch<VertexType, IndexType, 1, TextureRenderable<VertexType, IndexType> >::m_element_buffers[0]);
				glEnableVertexAttribArray(2);
				glEnableVertexAttribArray(3);
				glEnableVertexAttribArray(4);
				glEnableVertexAttribArray(5);
				glVertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, sizeof(Poseable2D), (void*)(0 * sizeof(vec4)));
				glVertexAttribPointer(3, 4, GL_FLOAT, GL_FALSE, sizeof(Poseable2D), (void*)(1 * sizeof(vec4)));
				glVertexAttribPointer(4, 4, GL_FLOAT, GL_FALSE, sizeof(Poseable2D), (void*)(2 * sizeof(vec4)));
				glVertexAttribPointer(5, 4, GL_FLOAT, GL_FALSE, sizeof(Poseable2D), (void*)(3 * sizeof(vec4)));

				glVertexAttribDivisor(0, 0); // Send the mesh data once
				glVertexAttribDivisor(1, 0); // Send the mesh data once
				glVertexAttribDivisor(2, 1); // Send the offset data for each instance drawn
				glVertexAttribDivisor(3, 1); // Send the offset data for each instance drawn
				glVertexAttribDivisor(4, 1); // Send the offset data for each instance drawn
				glVertexAttribDivisor(5, 1); // Send the offset data for each instance drawn
			}
		};
	}
}