polyvox/examples/DecodeOnGPU/main.cpp

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Copyright (c) 2015 David Williams and Matthew Williams

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#include "PolyVoxExample.h"

#include "PolyVox/CubicSurfaceExtractor.h"
#include "PolyVox/MarchingCubesSurfaceExtractor.h"
#include "PolyVox/Mesh.h"
#include "PolyVox/RawVolume.h"

#include <QApplication>

//Use the PolyVox namespace
using namespace PolyVox;

void createSphereInVolume(RawVolume<uint8_t>& volData, float fRadius)
{
	//This vector hold the position of the center of the volume
	Vector3DFloat v3dVolCenter(volData.getWidth() / 2, volData.getHeight() / 2, volData.getDepth() / 2);

	//This three-level for loop iterates over every voxel in the volume
	for (int z = 0; z < volData.getDepth(); z++)
	{
		for (int y = 0; y < volData.getHeight(); y++)
		{
			for (int x = 0; x < volData.getWidth(); x++)
			{
				//Store our current position as a vector...
				Vector3DFloat v3dCurrentPos(x, y, z);
				//And compute how far the current position is from the center of the volume
				float fDistToCenter = (v3dCurrentPos - v3dVolCenter).length();

				uint8_t uVoxelValue = 0;

				//If the current voxel is less than 'radius' units from the center then we make it solid.
				if (fDistToCenter <= fRadius)
				{
					//Our new voxel value
					uVoxelValue = 255;
				}

				//Wrte the voxel value into the volume	
				volData.setVoxel(x, y, z, uVoxelValue);
			}
		}
	}
}

class DecodeOnGPUExample : public PolyVoxExample
{
public:
	DecodeOnGPUExample(QWidget *parent)
		:PolyVoxExample(parent)
	{
	}

protected:
	void initializeExample() override
	{
		QSharedPointer<QGLShaderProgram> shader(new QGLShaderProgram);

		if (!shader->addShaderFromSourceFile(QGLShader::Vertex, ":/decode.vert"))
		{
			std::cerr << shader->log().toStdString() << std::endl;
			exit(EXIT_FAILURE);
		}

		if (!shader->addShaderFromSourceFile(QGLShader::Fragment, ":/decode.frag"))
		{
			std::cerr << shader->log().toStdString() << std::endl;
			exit(EXIT_FAILURE);
		}

		setShader(shader);

		//Create an empty volume and then place a sphere in it
		RawVolume<uint8_t> volData(PolyVox::Region(Vector3DInt32(0, 0, 0), Vector3DInt32(63, 63, 63)));
		createSphereInVolume(volData, 30);

		// Extract the surface for the specified region of the volume. Uncomment the line for the kind of surface extraction you want to see.
		//auto mesh = extractCubicMesh(&volData, volData.getEnclosingRegion());
		auto mesh = extractMarchingCubesMesh(&volData, volData.getEnclosingRegion());

		// The surface extractor outputs the mesh in an efficient compressed format which is not directly suitable for rendering. The easiest approach is to 
		// decode this on the CPU as shown below, though more advanced applications can upload the compressed mesh to the GPU and decompress in shader code.
		//auto decodedMesh = decodeMesh(mesh);

		//Pass the surface to the OpenGL window
		OpenGLMeshData meshData = buildOpenGLMeshData(mesh);
		addMeshData(meshData);

		setCameraTransform(QVector3D(100.0f, 100.0f, 100.0f), -(PI / 4.0f), PI + (PI / 4.0f));
	}

private:
	OpenGLMeshData buildOpenGLMeshData(const PolyVox::Mesh< PolyVox::MarchingCubesVertex< uint8_t > >& surfaceMesh, const PolyVox::Vector3DInt32& translation = PolyVox::Vector3DInt32(0, 0, 0), float scale = 1.0f)
	{
		// 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, surfaceMesh.getNoOfVertices() * sizeof(MarchingCubesVertex< uint8_t >), surfaceMesh.getRawVertexData(), 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, surfaceMesh.getNoOfIndices() * sizeof(uint32_t), surfaceMesh.getRawIndexData(), 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
		glVertexAttribIPointer(0, 3, GL_UNSIGNED_SHORT, sizeof(MarchingCubesVertex< uint8_t >), (GLvoid*)(offsetof(MarchingCubesVertex< uint8_t >, encodedPosition))); //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.
		glVertexAttribIPointer(1, 1, GL_UNSIGNED_SHORT, sizeof(MarchingCubesVertex< uint8_t >), (GLvoid*)(offsetof(MarchingCubesVertex< uint8_t >, encodedNormal)));

		// 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(uint8_t), size_t(4)); // Can't upload more that 4 components (vec4 is GLSL's biggest type)
		glVertexAttribIPointer(2, size, GL_UNSIGNED_BYTE, sizeof(MarchingCubesVertex< uint8_t >), (GLvoid*)(offsetof(MarchingCubesVertex< uint8_t >, 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 = surfaceMesh.getNoOfIndices();
		meshData.translation = QVector3D(translation.getX(), translation.getY(), translation.getZ());
		meshData.scale = scale;

		// Set 16 or 32-bit index buffer size.
		meshData.indexType = sizeof(PolyVox::Mesh< PolyVox::MarchingCubesVertex< uint8_t > >::IndexType) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT;

		return meshData;
	}
};

int main(int argc, char *argv[])
{
	//Create and show the Qt OpenGL window
	QApplication app(argc, argv);
	DecodeOnGPUExample openGLWidget(0);
	openGLWidget.show();

	//Run the message pump.
	return app.exec();
}