/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkLineIntegralConvolution2D.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
// .NAME vtkLineIntegralConvolution2D - GPU-based implementation of Line
//  Integral Convolution (LIC)
//
// .SECTION Description
//  This class resorts to GLSL to implement GPU-based Line Integral Convolution
//  (LIC) for visualizing a 2D vector field that may be obtained by projecting
//  an original 3D vector field onto a surface (such that the resulting 2D
//  vector at each grid point on the surface is tangential to the local normal,
//  as done in vtkSurfaceLICPainter).
//
//  As an image-based technique, 2D LIC works by (1) integrating a bidirectional
//  streamline from the center of each pixel (of the LIC output image), (2)
//  locating the pixels along / hit by this streamline as the correlated pixels
//  of the starting pixel (seed point / pixel), (3) indexing a (usually white)
//  noise texture (another input to LIC, in addition to the 2D vector field,
//  usually with the same size as that of the 2D vetor field) to determine the
//  values (colors) of these pixels (the starting and the correlated pixels),
//  typically through bi-linear interpolation, and (4) performing convolution
//  (weighted averaging) on these values, by adopting a low-pass filter (such
//  as box, ramp, and Hanning kernels), to obtain the result value (color) that
//  is then assigned to the seed pixel.
//
//  The GLSL-based GPU implementation herein maps the aforementioned pipeline to
//  fragment shaders and a box kernel is employed. Both the white noise and the
//  vector field are provided to the GPU as texture objects (supported by the
//  multi-texturing capability). In addition, there are four texture objects
//  (color buffers) allocated to constitute two pairs that work in a ping-pong
//  fashion, with one as the read buffers and the other as the write / render
//  targets. Maintained by a frame buffer object (GL_EXT_framebuffer_object),
//  each pair employs one buffer to store the current (dynamically updated)
//  position (by means of the texture coordinate that keeps being warped by the
//  underlying vector) of the (virtual) particle initially released from each
//  fragment while using the bother buffer to store the current (dynamically
//  updated too) accumulated texture value that each seed fragment (before the
//  'mesh' is warped) collects. Given NumberOfSteps integration steps in each
//  direction, there are a total of (2 * NumberOfSteps + 1) fragments (including
//  the seed fragment) are convolved and each contributes 1 / (2 * NumberOfSteps
//  + 1) of the associated texture value to fulfill the box filter.
//
//  One pass of LIC (basic LIC) tends to produce low-contrast / blurred images and
//  vtkLineIntegralConvolution2D provides an option for creating enhanced LIC
//  images. Enhanced LIC improves image quality by increasing inter-streamline
//  contrast while suppressing artifacts. It performs two passes of LIC, with a
//  3x3 Laplacian high-pass filter in between that processes the output of pass
//  #1 LIC and forwards the result as the input 'noise' to pass #2 LIC.
//
//  vtkLineIntegralConvolution2D applies masking to zero-vector fragments so
//  that un-filtered white noise areas are made totally transparent by class
//  vtkSurfaceLICPainter to show the underlying geometry surface.
//
//  The convolution process tends to decrease both contrast and dynamic range,
//  sometimes leading to dull dark images. In order to counteract this, optional
//  contrast ehnancement stages have been added. These increase the dynamic range and
//  contrast and sharpen streaking patterns that emerge from the LIC process.
//
//  Under some circumstances, typically depending on the contrast and dynamic
//  range and graininess of the noise texture, jagged or pixelated patterns emerge
//  in the LIC. These can be reduced by enabling the optional anti-aliasing pass.
//
//  The internal pipeline is as follows, with optional stages denoted by ()
//  nested optional stages depend on their parent stage.
//  <pre>
//   noise texture
//           |
//           [ LIC ((CE) HPF LIC) (AA) (CE) ]
//           |                              |
//  vector field                       LIC'd image
// </pre>
//  where LIC is the LIC stage, HPF is the high-pass filter stage, CE is the
//  contrast ehnacement stage, and AA is the antialias stage.
//
// .SECTION See Also
//  vtkSurfaceLICPainter vtkImageDataLIC2D vtkStructuredGridLIC2D

#ifndef vtkLineIntegralConvolution2D_h
#define vtkLineIntegralConvolution2D_h

#include "vtkObject.h"
#include "vtkWeakPointer.h" // for ren context
#include "vtkRenderingLICModule.h" // for export macro
#include <deque> // for deque

class vtkRenderWindow;
class vtkTextureObject;
class vtkPixelExtent;
class vtkShaderProgram2;
class vtkFrameBufferObject2;
class vtkPainterCommunicator;

class VTKRENDERINGLIC_EXPORT vtkLineIntegralConvolution2D : public vtkObject
{
public:
  static vtkLineIntegralConvolution2D *New();
  vtkTypeMacro(vtkLineIntegralConvolution2D, vtkObject);
  void PrintSelf(ostream & os, vtkIndent indent);

  // Description:
  // Returns if the context supports the required extensions.
  static bool IsSupported(vtkRenderWindow * renWin);

  // Description:
  // Set/Get the rendering context. A reference is not explicity held,
  // thus refernce to the context must be held externally.
  void SetContext(vtkRenderWindow *context);
  vtkRenderWindow *GetContext();

  // Description:
  // EnhancedLIC mean compute the LIC twice with the second pass using
  // the edge-enhanced result of the first pass as a noise texture. Edge
  // enhancedment is made by a simple Laplace convolution.
  vtkSetClampMacro(EnhancedLIC, int, 0, 1);
  vtkGetMacro(EnhancedLIC, int);
  vtkBooleanMacro(EnhancedLIC, int);

  // Description:
  // Enable/Disable contrast and dynamic range correction stages. Stage 1 is applied
  // on the input to the high-pass filter when the high-pass filter is enabled and
  // skipped otherwise. Stage 2, when enabled is the final stage in the internal
  // pipeline. Both stages are implemented by a histogram stretching of the gray scale
  // colors in the LIC'd image as follows:
  //
  //     c = (c-m)/(M-m)
  //
  // where, c is the fragment color, m is the color value to map to 0, M is the
  // color value to map to 1. The default values of m and M are the min and max
  // over all fragments.
  //
  // This increase the dynamic range and contrast in the LIC'd image, both of which
  //  are natuarly attenuated by the LI conovlution proccess.
  //
  //  ENHANCE_CONTRAST_OFF  -- don't enhance contrast
  //  ENHANCE_CONTRAST_ON   -- enhance high-pass input and final stage output
  //
  // This feature is disabled by default.
  enum {
    ENHANCE_CONTRAST_OFF=0,
    ENHANCE_CONTRAST_ON=1};
  vtkSetClampMacro(EnhanceContrast, int, 0, 2);
  vtkGetMacro(EnhanceContrast, int);
  vtkBooleanMacro(EnhanceContrast, int);

  // Description:
  // This feature is used to fine tune the contrast enhancement. Values are provided
  // indicating the fraction of the range to adjust m and M by during contrast enahncement
  // histogram stretching.  M and m are the intensity/lightness values that map to 1 and 0.
  // (see EnhanceContrast for an explanation of the mapping procedure). m and M are computed
  // using the factors as follows:
  //
  //     m = min(C) - mFactor * (max(C) - min(C))
  //     M = max(C) - MFactor * (max(C) - min(C))
  //
  // the default values for mFactor and MFactor are 0 which result in
  // m = min(C), M = max(C), where C is all of the colors in the image. Adjusting
  // mFactor and MFactor above zero provide a means to control the saturation of
  // normalization. These settings only affect the final normalization, the
  // normalization that occurs on the input to the high-pass filter always uses
  // the min and max.
  vtkSetClampMacro(LowContrastEnhancementFactor, double, 0.0, 1.0);
  vtkGetMacro(LowContrastEnhancementFactor, double);
  vtkSetClampMacro(HighContrastEnhancementFactor, double, 0.0, 1.0);
  vtkGetMacro(HighContrastEnhancementFactor, double);

  // Description:
  // Enable/Disable the anti-aliasing pass. This optional pass (disabled by
  // default) can be enabled to reduce jagged patterns in the final LIC image.
  // Values greater than 0 control the number of iterations, one is typically
  // sufficient.
  vtkSetClampMacro(AntiAlias, int, 0, VTK_INT_MAX);
  vtkGetMacro(AntiAlias, int);
  vtkBooleanMacro(AntiAlias, int);

  // Description:
  // Number of streamline integration steps (initial value is 1).
  // In term of visual quality, the greater (within some range) the better.
  vtkSetClampMacro(NumberOfSteps, int, 0, VTK_INT_MAX);
  vtkGetMacro(NumberOfSteps, int);

  // Description:
  // Get/Set the streamline integration step size (0.01 by default). This is
  // the length of each step in normalized image space i.e. in range [0, FLOAT_MAX].
  // In term of visual quality, the smaller the better. The type for the
  // interface is double as VTK interface is, but GPU only supports float.
  // Thus it will be converted to float in the execution of the algorithm.
  vtkSetClampMacro(StepSize, double, 0.0, VTK_FLOAT_MAX);
  vtkGetMacro(StepSize, double);

  // Description:
  // If VectorField has >= 3 components, we must choose which 2 components
  // form the (X, Y) components for the vector field. Must be in the range
  // [0, 3].
  void SetComponentIds(int c0, int c1);
  void SetComponentIds(int c[2]){ this->SetComponentIds(c[0], c[1]); }
  vtkGetVector2Macro(ComponentIds, int);

  // Description:
  // Set the max noise value for use during LIC integration normalization.
  // The integration normalization factor is the max noise value times the
  // number of steps taken. The default value is 1.
  vtkSetClampMacro(MaxNoiseValue, double, 0.0, 1.0);
  vtkGetMacro(MaxNoiseValue, double);

  // Description:
  // This class performs LIC in the normalized image space. Hence, by default
  // it transforms the input vectors to the normalized image space (using the
  // GridSpacings and input vector field dimensions). Set this to 0 to disable
  // tranformation if the vectors are already transformed.
  void SetTransformVectors(int val);
  vtkGetMacro(TransformVectors, int);

  // Description:
  // Set/Get the spacing in each dimension of the plane on which the vector
  // field is defined. This class performs LIC in the normalized image space
  // and hence generally it needs to transform the input vector field (given
  // in physical space) to the normalized image space. The Spacing is needed
  // to determine the transform. Default is (1.0, 1.0). It is possible to
  // disable vector transformation by setting TransformVectors to 0.
  //vtkSetVector2Macro(GridSpacings, double);
  //vtkGetVector2Macro(GridSpacings, double);

  // Description:
  // Normalize vectors during integration. When set(the default) the input vector field
  // is normalized during integration, and each integration occurs over the same arclength.
  // When not set each integration occurs over an arc length proportional to the field
  // magnitude as is customary in traditional numerical methods. See, "Imaging Vector
  // Fields Using Line Integral Convolution" for an axample where normalization is used.
  // See, "Image Space Based Visualization of Unsteady Flow on Surfaces" for an example
  // of where no normalization is used.
  void SetNormalizeVectors(int val);
  vtkGetMacro(NormalizeVectors, int);

  // Description:
  // The MaskThreshold controls blanking of the LIC texture. For fragments with
  // |V|<threhold the LIC fragment is not rendered. The default value is 0.0.
  //
  // For surface LIC MaskThreshold units are in the original vector space. For image LIC
  // be aware that while the vector field is transformed to image space while the mask
  // threshold is not. Therefore the mask threshold must be specified in image space
  // units.
  vtkSetClampMacro(MaskThreshold, double, -1.0, VTK_FLOAT_MAX);
  vtkGetMacro(MaskThreshold, double);


  // Description:
  // Compute the lic on the entire vector field texture.
  vtkTextureObject *Execute(
        vtkTextureObject *vectorTex,
        vtkTextureObject *noiseTex);

  // Description:
  // Compute the lic on the indicated subset of the vector field
  // texture.
  vtkTextureObject *Execute(
        const int extent[4],
        vtkTextureObject *vectorTex,
        vtkTextureObject *noiseTex);

  // Description:
  // Compute LIC over the desired subset of the input texture. The
  // result is copied into the desired subset of the provided output
  // texture.
  //
  // inputTexExtent  : screen space extent of the input texture
  // vectorExtent    : part of the inpute extent that has valid vectors
  // licExtent       : part of the inpute extent to compute on
  // outputTexExtent : screen space extent of the output texture
  // outputExtent    : part of the output texture to store the result
  //
  vtkTextureObject *Execute(
        const vtkPixelExtent &inputTexExtent,
        const std::deque<vtkPixelExtent> &vectorExtent,
        const std::deque<vtkPixelExtent> &licExtent,
        vtkTextureObject *vectorTex,
        vtkTextureObject *maskVectorTex,
        vtkTextureObject *noiseTex);

  // Description:
  // Convenience functions to ensure that the input textures are
  // configured correctly.
  static
  void SetVectorTexParameters(vtkTextureObject *vectors);

  static
  void SetNoiseTexParameters(vtkTextureObject *noise);

  // Description:
  // Set the communicator to use during parallel operation
  // The communicator will not be duplicated or reference
  // counted for performance reasons thus caller should
  // hold/manage reference to the communicator during use
  // of the LIC object.
  virtual void SetCommunicator(vtkPainterCommunicator *){}
  virtual vtkPainterCommunicator *GetCommunicator();

  // Description:
  // For parallel operation, find global min/max
  // min/max are in/out.
  virtual void GetGlobalMinMax(
        vtkPainterCommunicator*,
        float&,
        float&) {}

  // Description:
  // Methods used for parallel benchmarks. Use cmake to define
  // vtkLineIntegralConviolution2DTIME to enable benchmarks.
  // During each update timing information is stored, it can
  // be written to disk by calling WriteLog.
  virtual void WriteTimerLog(const char *){}

protected:
  vtkLineIntegralConvolution2D();
  virtual ~vtkLineIntegralConvolution2D();

  void SetVTShader(vtkShaderProgram2 *prog);
  void SetLIC0Shader(vtkShaderProgram2 *prog);
  void SetLICIShader(vtkShaderProgram2 *prog);
  void SetLICNShader(vtkShaderProgram2 *prog);
  void SetEEShader(vtkShaderProgram2 *prog);
  void SetCEShader(vtkShaderProgram2 *prog);
  void SetAAHShader(vtkShaderProgram2 *prog);
  void SetAAVShader(vtkShaderProgram2 *prog);

  void BuildShaders();

  void RenderQuad(
        float computeBounds[4],
        vtkPixelExtent computeExtent);

  vtkTextureObject *AllocateBuffer(unsigned int texSize[2]);

  // Description:
  // Convenience functions to ensure that the input textures are
  // configured correctly.
  void SetNoise2TexParameters(vtkTextureObject *noise);

  // Description:
  // Methods used for parallel benchmarks. Use cmake to define
  // vtkSurfaceLICPainterTIME to enable benchmarks. During each
  // update timing information is stored, it can be written to
  // disk by calling WriteLog (defined in vtkSurfaceLICPainter).
  virtual void StartTimerEvent(const char *){}
  virtual void EndTimerEvent(const char *){}

protected:
  vtkPainterCommunicator *Comm;

  vtkWeakPointer<vtkRenderWindow> Context;
  vtkFrameBufferObject2 *FBO;

  int ShadersNeedBuild;
  vtkShaderProgram2 *VTShader;
  vtkShaderProgram2 *LIC0Shader;
  vtkShaderProgram2 *LICIShader;
  vtkShaderProgram2 *LICNShader;
  vtkShaderProgram2 *EEShader;
  vtkShaderProgram2 *CEShader;
  vtkShaderProgram2 *AAHShader;
  vtkShaderProgram2 *AAVShader;

  int     NumberOfSteps;
  double  StepSize;
  int     EnhancedLIC;
  int     EnhanceContrast;
  double  LowContrastEnhancementFactor;
  double  HighContrastEnhancementFactor;
  int     AntiAlias;
  int     NoiseTextureLookupCompatibilityMode;
  double  MaskThreshold;
  int     TransformVectors;
  int     NormalizeVectors;
  int     ComponentIds[2];
  double  MaxNoiseValue;

private:
  vtkLineIntegralConvolution2D(const vtkLineIntegralConvolution2D &); // Not implemented.
  void operator = (const vtkLineIntegralConvolution2D &);             // Not implemented.
};

#endif
