From 4cec89de384169f77b56aaa0da0dec4c41162e66 Mon Sep 17 00:00:00 2001
From: David Williams <david@volumesoffun.com>
Date: Fri, 23 May 2014 14:32:46 +0200
Subject: [PATCH] Added ability to specify the visible region  so that the
 example framework can support different volume sizes.

---
 examples/Basic/OpenGLWidget.cpp | 19 +++++++++++++++----
 examples/Basic/OpenGLWidget.h   |  5 +++--
 examples/Basic/main.cpp         |  1 +
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/examples/Basic/OpenGLWidget.cpp b/examples/Basic/OpenGLWidget.cpp
index 17355b2f..eb47180e 100644
--- a/examples/Basic/OpenGLWidget.cpp
+++ b/examples/Basic/OpenGLWidget.cpp
@@ -9,8 +9,7 @@ using namespace std;
 
 OpenGLWidget::OpenGLWidget(QWidget *parent)
 	:QGLWidget(parent)
-	,mCenterPoint(32,32,32)
-	,mDistFromCenter(50)
+	,m_viewableRegion(Region(0, 0, 0, 255, 255, 255))
 	,m_xRotation(0)
 	,m_yRotation(0)
 {
@@ -51,6 +50,12 @@ void OpenGLWidget::setSurfaceMeshToRender(const PolyVox::SurfaceMesh<CubicVertex
 	mMeshData.push_back(meshData);
 }
 
+void OpenGLWidget::setViewableRegion(Region viewableRegion)
+{
+	m_viewableRegion = viewableRegion;
+	setupWorldToCameraMatrix();
+}
+
 void OpenGLWidget::initializeGL()
 {
 	GLenum err = glewInit();
@@ -209,11 +214,17 @@ void OpenGLWidget::setupWorldToCameraMatrix()
 {
 	shader.bind();
 
+	QVector3D lowerCorner(m_viewableRegion.getLowerX(), m_viewableRegion.getLowerY(), m_viewableRegion.getLowerZ());
+	QVector3D upperCorner(m_viewableRegion.getUpperX(), m_viewableRegion.getUpperY(), m_viewableRegion.getUpperZ());
+
+	QVector3D centerPoint = (lowerCorner + upperCorner) * 0.5;
+	float fDiagonalLength = (upperCorner - lowerCorner).length();
+
 	QMatrix4x4 worldToCameraMatrix{};
-	worldToCameraMatrix.translate(0, 0, -mDistFromCenter); //Move the camera back by the required amount
+	worldToCameraMatrix.translate(0, 0, -fDiagonalLength / 2.0f); //Move the camera back by the required amount
 	worldToCameraMatrix.rotate(m_xRotation, 0, 1, 0); //rotate around y-axis
 	worldToCameraMatrix.rotate(m_yRotation, 1, 0, 0); //rotate around x-axis
-	worldToCameraMatrix.translate(-mCenterPoint); //centre the model on the origin
+	worldToCameraMatrix.translate(-centerPoint); //centre the model on the origin
 
 	shader.setUniformValue("worldToCameraMatrix", worldToCameraMatrix);
 
diff --git a/examples/Basic/OpenGLWidget.h b/examples/Basic/OpenGLWidget.h
index 5e7e46d9..9009bad8 100644
--- a/examples/Basic/OpenGLWidget.h
+++ b/examples/Basic/OpenGLWidget.h
@@ -52,6 +52,8 @@ public:
 	//Convert a SurfaceMesh to OpenGL index/vertex buffers
 	void setSurfaceMeshToRender(const PolyVox::SurfaceMesh<PolyVox::CubicVertex<uint8_t> >& surfaceMesh);
 
+	void setViewableRegion(PolyVox::Region viewableRegion);
+
 protected:
 	//Qt OpenGL functions
 	void initializeGL();
@@ -72,8 +74,7 @@ private:
 	QPoint m_CurrentMousePos;
 
 	//Camera setup
-	QVector3D mCenterPoint;
-	float mDistFromCenter;
+	PolyVox::Region m_viewableRegion;
 	int m_xRotation;
 	int m_yRotation;
 };
diff --git a/examples/Basic/main.cpp b/examples/Basic/main.cpp
index 78de21d4..82031152 100644
--- a/examples/Basic/main.cpp
+++ b/examples/Basic/main.cpp
@@ -86,6 +86,7 @@ int main(int argc, char *argv[])
 
 	//Pass the surface to the OpenGL window
 	openGLWidget.setSurfaceMeshToRender(mesh);
+	openGLWidget.setViewableRegion(volData.getEnclosingRegion());
 	//openGLWidget.setSurfaceMeshToRender(mesh2);
 
 	//Run the message pump.