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      1 /*
      2  * Copyright (C) 2010 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  *
     14  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     15  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     17  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     18  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     19  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     20  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     21  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #ifndef LoopBlinnTextureCoords_h
     27 #define LoopBlinnTextureCoords_h
     28 
     29 #include "FloatPoint3D.h"
     30 #include "LoopBlinnClassifier.h"
     31 #include "LoopBlinnConstants.h"
     32 
     33 #include <wtf/Noncopyable.h>
     34 
     35 namespace WebCore {
     36 
     37 // Computes three-dimensional texture coordinates for the control
     38 // points of a cubic curve for rendering via the shader in "Rendering
     39 // Vector Art on the GPU" by Loop and Blinn, GPU Gems 3, Chapter 25.
     40 class LoopBlinnTextureCoords {
     41 public:
     42     // Container for the cubic texture coordinates and other associated
     43     // information.
     44     struct Result {
     45         Result()
     46             : isLineOrPoint(false)
     47             , hasRenderingArtifact(false)
     48             , subdivisionParameterValue(0.0f) { }
     49 
     50         // The (k, l, m) texture coordinates that are to be associated
     51         // with the four control points of the cubic curve.
     52         FloatPoint3D klmCoordinates[4];
     53 
     54         // Indicates whether the curve is a line or a point, in which case
     55         // we do not need to add its triangles to the mesh.
     56         bool isLineOrPoint;
     57 
     58         // For the loop case, indicates whether a rendering artifact was
     59         // detected, in which case the curve needs to be further
     60         // subdivided.
     61         bool hasRenderingArtifact;
     62 
     63         // If a rendering artifact will occur for the given loop curve,
     64         // this is the parameter value (0 <= value <= 1) at which the
     65         // curve needs to be subdivided to fix the artifact.
     66         float subdivisionParameterValue;
     67     };
     68 
     69     // Computes the texture coordinates for a cubic curve segment's
     70     // control points, given the classification of the curve as well as
     71     // an indication of which side is to be filled.
     72     static Result compute(const LoopBlinnClassifier::Result& classification,
     73                           LoopBlinnConstants::FillSide sideToFill);
     74 
     75 private:
     76     // This class does not need to be instantiated.
     77     LoopBlinnTextureCoords() { }
     78 };
     79 
     80 } // namespace WebCore
     81 
     82 #endif // LoopBlinnTextureCoords_h
     83