polyvox/examples/common/PolyVoxExample.h

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

This software is provided 'as-is', without any express or implied
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Permission is granted to anyone to use this software for any purpose,
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appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.

3. This notice may not be removed or altered from any source
distribution.
*******************************************************************************/

#ifndef __PolyVoxExample_H__
#define __PolyVoxExample_H__

#include "OpenGLWidget.h"

// 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;
};

class PolyVoxExample : public OpenGLWidget<QOpenGLFunctions_3_1>
{
public:
	PolyVoxExample(QWidget *parent)
		:OpenGLWidget(parent)
	{
	}

	// 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);

	// 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(typename 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(typename 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(typename MeshType::VertexType), (GLvoid*)(offsetof(typename 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(typename MeshType::VertexType), (GLvoid*)(offsetof(typename 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(typename 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(typename MeshType::VertexType), (GLvoid*)(offsetof(typename 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(typename 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);
	}

protected:
	const float PI = 3.14159265358979f;

	virtual void initializeExample() {};

	void initialize() override
	{
		mShader = QSharedPointer<QGLShaderProgram>(new QGLShaderProgram);

		// This is basically a simple fallback vertex shader which does the most basic rendering possible.  
		// PolyVox examples are able to provide their own shaders to demonstrate certain effects if desired. 
		if (!mShader->addShaderFromSourceFile(QGLShader::Vertex, ":/example.vert"))
		{
			std::cerr << mShader->log().toStdString() << std::endl;
			exit(EXIT_FAILURE);
		}

		// This is basically a simple fallback fragment shader which does the most basic rendering possible.  
		// PolyVox examples are able to provide their own shaders to demonstrate certain effects if desired. 
		if (!mShader->addShaderFromSourceFile(QGLShader::Fragment, ":/example.frag"))
		{
			std::cerr << mShader->log().toStdString() << std::endl;
			exit(EXIT_FAILURE);
		}

		// Bind the position semantic - this is defined in the vertex shader above.
		mShader->bindAttributeLocation("position", 0);

		// Bind the other semantics. Note that these don't actually exist in our example shader above! However, other
		// example shaders may choose to provide them and having the binding code here does not seem to cause any problems.
		mShader->bindAttributeLocation("normal", 1);
		mShader->bindAttributeLocation("material", 2);

		if (!mShader->link())
		{
			std::cerr << mShader->log().toStdString() << std::endl;
			exit(EXIT_FAILURE);
		}

		// Now do any initialization for the specific example.
		initializeExample();
	}

	void renderOneFrame() override
	{
		// Our example framework only uses a single shader for the scene (for all meshes).
		mShader->bind();

		// These two matrices are constant for all meshes.
		mShader->setUniformValue("viewMatrix", viewMatrix());
		mShader->setUniformValue("projectionMatrix", projectionMatrix());

		// Iterate over each mesh which the user added to our list, and render it.
		for (OpenGLMeshData meshData : mMeshData)
		{
			//Set up the model matrrix based on provided translation and scale.
			QMatrix4x4 modelMatrix;
			modelMatrix.translate(meshData.translation);
			modelMatrix.scale(meshData.scale);
			mShader->setUniformValue("modelMatrix", modelMatrix);

			// Bind the vertex array for the current mesh
			glBindVertexArray(meshData.vertexArrayObject);
			// Draw the mesh
			glDrawElements(GL_TRIANGLES, meshData.noOfIndices, meshData.indexType, 0);
			// Unbind the vertex array.
			glBindVertexArray(0);
		}

		// We're done with the shader for this frame.
		mShader->release();
	}

private:
	// Index/vertex buffer data
	std::vector<OpenGLMeshData> mMeshData;

	QSharedPointer<QGLShaderProgram> mShader;
};

#endif //__PolyVoxExample_H__