From 4b560f03201f1c2d7c632126cd1e512ed4027072 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 26 Apr 2023 01:16:06 +0100
Subject: Add Mesh helper for drawing instances

Assumes the supplied VAO was created and configured for the mesh it's passed back to.
---
 gfx/models/mesh.cpp | 10 ++++++++++
 gfx/models/mesh.h   |  1 +
 2 files changed, 11 insertions(+)

diff --git a/gfx/models/mesh.cpp b/gfx/models/mesh.cpp
index 55759cb..3faf252 100644
--- a/gfx/models/mesh.cpp
+++ b/gfx/models/mesh.cpp
@@ -42,3 +42,13 @@ Mesh::Draw() const
 
 	glBindVertexArray(0);
 }
+
+void
+Mesh::DrawInstanced(GLuint vao, GLsizei count) const
+{
+	glBindVertexArray(vao);
+
+	glDrawElementsInstanced(mode, m_numIndices, GL_UNSIGNED_INT, nullptr, count);
+
+	glBindVertexArray(0);
+}
diff --git a/gfx/models/mesh.h b/gfx/models/mesh.h
index 472b7ed..a2205a1 100644
--- a/gfx/models/mesh.h
+++ b/gfx/models/mesh.h
@@ -14,6 +14,7 @@ public:
 	Mesh(const std::span<const Vertex> vertices, const std::span<const unsigned int> indices, GLenum = GL_TRIANGLES);
 
 	void Draw() const;
+	void DrawInstanced(GLuint vao, GLsizei count) const;
 	VertexArrayObject & configureVAO(VertexArrayObject &&) const;
 	GLsizei count() const;
 	GLenum type() const;
-- 
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