root/OpenSceneGraph/trunk/include/osg/TransferFunction @ 13041

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1/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
2 *
3 * This library is open source and may be redistributed and/or modified under
4 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
5 * (at your option) any later version.  The full license is in LICENSE file
6 * included with this distribution, and on the openscenegraph.org website.
7 *
8 * This library is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11 * OpenSceneGraph Public License for more details.
12*/
13
14#ifndef OSG_TRANSFERFUNCTION
15#define OSG_TRANSFERFUNCTION 1
16
17#include <osg/Texture>
18#include <osg/Shader>
19
20#include <map>
21
22namespace osg {
23
24
25/** TransferFunction is a class that provide a 1D,2D or 3D colour look up table
26  * that can be used on the GPU as a 1D, 2D or 3D texture.
27  * Typically uses include mapping heights to colours when contouring terrain,
28  * or mapping intensities to colours when volume rendering.
29*/
30class OSG_EXPORT TransferFunction : public osg::Object
31{
32    public :
33
34        TransferFunction();
35
36       /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
37        TransferFunction(const TransferFunction& tf, const CopyOp& copyop=CopyOp::SHALLOW_COPY);
38
39        META_Object(osg, TransferFunction)
40
41        /** Get the image that is used for passing the transfer function data to the GPU.*/
42        osg::Image* getImage() { return _image.get(); }
43
44        /** Get the const image that is used for passing the transfer function data to the GPU.*/
45        const osg::Image* getImage() const { return _image.get(); }
46
47    protected:
48
49        virtual ~TransferFunction();
50
51        osg::ref_ptr<osg::Image>    _image;
52};
53
54/** 1D variant of TransferFunction. */
55class OSG_EXPORT TransferFunction1D : public osg::TransferFunction
56{
57    public:
58
59        TransferFunction1D();
60
61       /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
62        TransferFunction1D(const TransferFunction1D& tf, const CopyOp& copyop=CopyOp::SHALLOW_COPY);
63
64        META_Object(osg, TransferFunction1D)
65
66        /** Get the minimum transfer function value.*/
67        float getMinimum() const { return _colorMap.empty() ? 0.0f : _colorMap.begin()->first; }
68
69        /** Get the maximum transfer function value.*/
70        float getMaximum() const { return _colorMap.empty() ? 0.0f : _colorMap.rbegin()->first; }
71
72        /** allocate the osg::Image with specified dimension.  The Image tracks the color map, and is used to represent the
73          * transfer function when download to GPU.*/
74        void allocate(unsigned int numImageCells);
75
76        /** Clear the whole range to just represent a single color.*/
77        void clear(const osg::Vec4& color = osg::Vec4(1.0f,1.0f,1.0f,1.0f));
78
79        /** Get pixel value from the image. */
80        osg::Vec4 getPixelValue(unsigned int i) const
81        {
82            if (_image.valid() && i<static_cast<unsigned int>(_image->s()))
83            {
84                return *reinterpret_cast<osg::Vec4*>(_image->data(i));
85            }
86            else
87            {
88                return osg::Vec4(1.0f,1.0f,1.0f,1.0f);
89            }
90        }
91
92        /** Get the number of image cells that are assigned to the represent the transfer function when download to the GPU.*/
93        unsigned int getNumberImageCells() const { return _image.valid() ? _image->s() : 0; }
94
95        /** Set the color for a specified transfer function value.
96          * updateImage defaults to true, and tells the setColor function to update the associate osg::Image that
97          * tracks the color map.  Pass in false as the updateImage parameter if you are setting up many values
98          * at once to avoid recomputation of the image data, then once all setColor calls are made explictly call
99          * updateImage() to bring the osg::Image back into sync with the color map. */
100        void setColor(float v, const osg::Vec4& color, bool updateImage=true);
101
102        /** Get the color for a specified transfer function value, interpolating the value if no exact match is found.*/
103        osg::Vec4 getColor(float v) const;
104
105        typedef std::map<float, osg::Vec4> ColorMap;
106
107        /** Get the color map that stores the mapping between the the transfer function value and the colour it maps to.*/
108        ColorMap& getColorMap() { return _colorMap; }
109
110        /** Get the const color map that stores the mapping between the the transfer function value and the colour it maps to.*/
111        const ColorMap& getColorMap() const { return _colorMap; }
112
113        /** Assign a color map and automatically update the image to make sure they are in sync.*/
114        void assign(const ColorMap& vcm);
115
116        /** Manually update the associate osg::Image to represent the colors assigned in the color map.*/
117        void updateImage();
118
119    protected:
120
121        ColorMap _colorMap;
122
123        void assignToImage(float lower_v, const osg::Vec4& lower_c, float upper_v, const osg::Vec4& upper_c);
124};
125
126}
127
128#endif
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