115 lines
5.3 KiB
C++
115 lines
5.3 KiB
C++
/*******************************************************************************
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Copyright (c) 2005-2009 David Williams
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source
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distribution.
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*******************************************************************************/
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#include "OpenGLWidget.h"
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#include "PolyVoxCore/CubicSurfaceExtractor.h"
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#include "PolyVoxCore/MarchingCubesSurfaceExtractor.h"
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#include "PolyVoxCore/Mesh.h"
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#include "PolyVoxCore/SimpleVolume.h"
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#include <QApplication>
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//Use the PolyVox namespace
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using namespace PolyVox;
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void createSphereInVolume(SimpleVolume<uint8_t>& volData, float fRadius)
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{
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//This vector hold the position of the center of the volume
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Vector3DFloat v3dVolCenter(volData.getWidth() / 2, volData.getHeight() / 2, volData.getDepth() / 2);
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//This three-level for loop iterates over every voxel in the volume
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for (int z = 0; z < volData.getDepth(); z++)
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{
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for (int y = 0; y < volData.getHeight(); y++)
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{
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for (int x = 0; x < volData.getWidth(); x++)
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{
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//Store our current position as a vector...
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Vector3DFloat v3dCurrentPos(x,y,z);
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//And compute how far the current position is from the center of the volume
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float fDistToCenter = (v3dCurrentPos - v3dVolCenter).length();
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// We actually want our volume to have high values in the center and low values as we move out, because our
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// eath should be a solid sphere surrounded by empty space. If we invert the distance then this is a step in
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// the right direction. We still have zero in the center, but lower (negative) values as we move out.
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float density = -fDistToCenter;
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// By adding the 'planetRadius' we now have a function which starts at 'planetRadius' and still decreases as it
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// moves out. The function passes through zero at a distance of 'planetRadius' and then continues do decrease
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// as it gets even further out.
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density += fRadius;
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// Ideally we would like our final density value to be '255' for voxels inside the planet and '0' for voxels
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// outside the planet. At the surface there should be a transition but this should occur not too quickly and
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// not too slowly, as both of these will result in a jagged appearance to the mesh.
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//
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// We probably want the transition to occur over a few voxels, whereas it currently occurs over 255 voxels
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// because it was derived from the distance. By scaling the density field we effectivly compress the rate
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// at which it changes at the surface. We also make the center much too high and the outside very low, but
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// we will clamp these to the corect range later.
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//
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// Note: You can try commenting out or changing the value on this line to see the effect it has.
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density *= 50;
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// Until now we've been defining our density field as if the threshold was at zero, with positive densities
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// being solid and negative densities being empty. But actually Cubiquity operates on the range 0 to 255, and
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// uses a threashold of 127 to decide where to place the generated surface. Therefore we shift and clamp our
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// density value and store it in a byte.
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density += 127;
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uint8_t uVoxelValue = (uint8_t)(clamp(density, 0.0f, 255.0f));
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//Wrte the voxel value into the volume
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volData.setVoxelAt(x, y, z, uVoxelValue);
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}
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}
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}
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}
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int main(int argc, char *argv[])
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{
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//Create and show the Qt OpenGL window
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QApplication app(argc, argv);
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OpenGLWidget openGLWidget(0);
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openGLWidget.show();
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//Create an empty volume and then place a sphere in it
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SimpleVolume<uint8_t> volData(PolyVox::Region(Vector3DInt32(0,0,0), Vector3DInt32(31, 31, 31)));
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createSphereInVolume(volData, 15);
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// Extract the surface for the specified region of the volume. Uncomment the line for the kind of surface extraction you want to see.
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//auto mesh = extractCubicMesh(&volData, volData.getEnclosingRegion());
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auto mesh = extractMarchingCubesMesh(&volData, volData.getEnclosingRegion());
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// The surface extractor outputs the mesh in an efficient compressed format which is not directly suitable for rendering. The easiest approach is to
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// 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.
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auto decodedMesh = decode(mesh);
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//Pass the surface to the OpenGL window
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openGLWidget.addMesh(decodedMesh);
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//openGLWidget.addMesh(mesh2);
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openGLWidget.setViewableRegion(volData.getEnclosingRegion());
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//Run the message pump.
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return app.exec();
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} |