polyvox/examples/common/OpenGLWidget.h

/*******************************************************************************
Copyright (c) 2005-2009 David Williams

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Permission is granted to anyone to use this software for any purpose,
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3. This notice may not be removed or altered from any source
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*******************************************************************************/

#ifndef __BasicExample_OpenGLWidget_H__
#define __BasicExample_OpenGLWidget_H__

#include "PolyVoxCore/Mesh.h"

#include "glew/glew.h"

#include <QGLWidget>
#include <QGLShaderProgram>

// This structure holds all the data required
// to render one of our meshes through OpenGL. 
struct OpenGLMeshData
{
	GLuint noOfIndices;
	GLenum indexType;
	GLuint indexBuffer;
	GLuint vertexBuffer;
	GLuint vertexArrayObject;
	QVector3D translation;
	float scale;
};

// Our OpenGLWidget is used by all the examples to render the extracted meshes. It is
// fairly specific to our needs (you probably won't want to use it in your own project)
// but should provide a useful illustration of how PolyVox meshes can be rendered.
class OpenGLWidget : public QGLWidget
{
public:
	// Constructor
	OpenGLWidget(QWidget *parent);

	// Convert a PolyVox mesh to OpenGL index/vertex buffers. Inlined because it's templatised.
	template <typename MeshType>
	void addMesh(const MeshType& surfaceMesh, const PolyVox::Vector3DInt32& translation = PolyVox::Vector3DInt32(0, 0, 0), float scale = 1.0f)
	{
		// Convienient access to the vertices and indices
		const auto& vecIndices = surfaceMesh.getIndices();
		const auto& vecVertices = surfaceMesh.getVertices();

		// This struct holds the OpenGL properties (buffer handles, etc) which will be used
		// to render our mesh. We copy the data from the PolyVox mesh into this structure.
		OpenGLMeshData meshData;

		// Create the VAO for the mesh
		glGenVertexArrays(1, &(meshData.vertexArrayObject));
		glBindVertexArray(meshData.vertexArrayObject);

		// The GL_ARRAY_BUFFER will contain the list of vertex positions
		glGenBuffers(1, &(meshData.vertexBuffer));
		glBindBuffer(GL_ARRAY_BUFFER, meshData.vertexBuffer);
		glBufferData(GL_ARRAY_BUFFER, vecVertices.size() * sizeof(MeshType::VertexType), vecVertices.data(), GL_STATIC_DRAW);

		// and GL_ELEMENT_ARRAY_BUFFER will contain the indices
		glGenBuffers(1, &(meshData.indexBuffer));
		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, meshData.indexBuffer);
		glBufferData(GL_ELEMENT_ARRAY_BUFFER, vecIndices.size() * sizeof(MeshType::IndexType), vecIndices.data(), GL_STATIC_DRAW);

		// Every surface extractor outputs valid positions for the vertices, so tell OpenGL how these are laid out
		glEnableVertexAttribArray(0); // Attrib '0' is the vertex positions
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(MeshType::VertexType), (GLvoid*)(offsetof(MeshType::VertexType, position))); //take the first 3 floats from every sizeof(decltype(vecVertices)::value_type)

		// Some surface extractors also generate normals, so tell OpenGL how these are laid out. If a surface extractor
		// does not generate normals then nonsense values are written into the buffer here and sghould be ignored by the
		// shader. This is mostly just to simplify this example code - in a real application you will know whether your
		// chosen surface extractor generates normals and can skip uploading them if not.
		glEnableVertexAttribArray(1); // Attrib '1' is the vertex normals.
		glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(MeshType::VertexType), (GLvoid*)(offsetof(MeshType::VertexType, normal)));

		// Finally a surface extractor will probably output additional data. This is highly application dependant. For this example code 
		// we're just uploading it as a set of bytes which we can read individually, but real code will want to do something specialised here.
		glEnableVertexAttribArray(2); //We're talking about shader attribute '2'
		GLint size = (std::min)(sizeof(MeshType::VertexType::DataType), size_t(4)); // Can't upload more that 4 components (vec4 is GLSL's biggest type)
		glVertexAttribIPointer(2, size, GL_UNSIGNED_BYTE, sizeof(MeshType::VertexType), (GLvoid*)(offsetof(MeshType::VertexType, data)));

		// We're done uploading and can now unbind.
		glBindVertexArray(0);

		// A few additional properties can be copied across for use during rendering.
		meshData.noOfIndices = vecIndices.size();
		meshData.translation = QVector3D(translation.getX(), translation.getY(), translation.getZ());
		meshData.scale = scale;

		// Set 16 or 32-bit index buffer size.
		meshData.indexType = sizeof(MeshType::IndexType) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT;

		// Now add the mesh to the list of meshes to render.
		addMeshData(meshData);
	}

	void addMeshData(OpenGLMeshData meshData)
	{
		mMeshData.push_back(meshData);
	}

	// For our purposes we use a single shader for the whole volume, and
	// this example framework is only meant to show a single volume at a time
	void setShader(QSharedPointer<QGLShaderProgram> shader);

	// The viewable region can be adjusted so that this example framework can be used for different volume sizes.
	void setViewableRegion(PolyVox::Region viewableRegion);

	// Mouse handling
	void mouseMoveEvent(QMouseEvent* event);
	void mousePressEvent(QMouseEvent* event);

protected:

	// Qt OpenGL functions
	void initializeGL();
	void resizeGL(int w, int h);
	void paintGL();

private:

	void setupWorldToCameraMatrix();

	// Index/vertex buffer data
	std::vector<OpenGLMeshData> mMeshData;
	
	QSharedPointer<QGLShaderProgram> mShader;

	// Matrices
	QMatrix4x4 worldToCameraMatrix;
	QMatrix4x4 cameraToClipMatrix;

	// Mouse data
	QPoint m_LastFrameMousePos;
	QPoint m_CurrentMousePos;

	// Camera setup
	PolyVox::Region m_viewableRegion;
	int m_xRotation;
	int m_yRotation;
};

#endif //__BasicExample_OpenGLWidget_H__