// Sh: A GPU metaprogramming language.//// Copyright 2003-2005 Serious Hack Inc.// // This library is free software; you can redistribute it and/or// modify it under the terms of the GNU Lesser General Public// License as published by the Free Software Foundation; either// version 2.1 of the License, or (at your option) any later version.//// This library is distributed in the hope that it will be useful,// but WITHOUT ANY WARRANTY; without even the implied warranty of// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU// Lesser General Public License for more details.//// You should have received a copy of the GNU Lesser General Public// License along with this library; if not, write to the Free Software// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, // MA  02110-1301, USA//////////////////////////////////////////////////////////////////////////////#include <sh/sh.hpp>#include <sh/shutil.hpp>#include <iostream>#include "Shader.hpp"#include "Globals.hpp"using namespace SH;using namespace ShUtil;#include "util.hpp"class Checkerboard : public Shader {public:  Checkerboard(bool aa);  ~Checkerboard();  bool init();  ShProgram vertex() { return vsh;}  ShProgram fragment() { return fsh;}private:  ShProgram vsh, fsh;    bool m_aa;  static bool m_done_init;  static ShAttrib1f m_frequency;  static ShColor3f m_color1, m_color2;};Checkerboard::Checkerboard(bool aa)  : Shader(std::string("Tiling: Checkerboard") + (aa ? ": Antialiased" : ": Aliased")),    m_aa(aa){  if (!m_done_init) {    // Initialize static variables    m_frequency.name("Frequency");    m_frequency.range(0.0, 10.0);    SH_NAME(m_color1);    SH_NAME(m_color2);    m_done_init = true;  }}Checkerboard::~Checkerboard(){}ShColor3f debugScalar(const ShAttrib1f& scalar){  return scalar * cond(scalar < 0.0,                       ShConstColor3f(-1.0, 0.0, 0.0),                       ShConstColor3f( 0.0, 1.0, 0.0));}bool Checkerboard::init(){  std::cerr << "Initializing " << name() << std::endl;  vsh = ShKernelLib::shVsh( Globals::mv, Globals::mvp );  vsh = shSwizzle("texcoord", "posh") << vsh;  ShAttrib1f SH_DECL(scale) = 1.0;  scale.range(1.0, 10.0);      fsh = SH_BEGIN_FRAGMENT_PROGRAM {    ShInputTexCoord2f tc;    ShOutputColor3f o;    ShAttrib2f checkpos = frac(tc * m_frequency);    // This is based on the "Antialised Checkerboard Fragment Shader"    // from the book "OpenGL Shading Language" by Randi Rost,    // pp. 350--351, Addison-Wesley.    // The original is of course written in GLSL.    if (m_aa) {      ShColor3f avgcolor = lerp(ShConstAttrib1f(0.5f), m_color1, m_color2);      ShAttrib2f fw = fwidth(tc);      ShAttrib2f fuzz = fw * m_frequency * 2.0;            ShAttrib1f fuzzMax = SH::max(fuzz(0), fuzz(1));            ShAttrib2f p = linstep(checkpos, 0.5f + fuzz * 0.5f, fuzz) +        (1.0  - linstep(checkpos, 0.5f * fuzz, fuzz));            o = lerp(p(0)*p(1) + (1.0 - p(0)) * (1.0 - p(1)), m_color2, m_color1);      o = lerp(linstep(fuzzMax, ShConstAttrib1f(0.3125), ShConstAttrib1f(0.375)), avgcolor, o);    } else {      o = lerp(checkpos(0)*checkpos(1) + (1.0 - checkpos(0))*(1.0 - checkpos(1)) >= 0.5,               m_color2, m_color1);    }  } SH_END_PROGRAM;  return true;}bool Checkerboard::m_done_init = false;ShAttrib1f Checkerboard::m_frequency = ShAttrib1f(1.0);ShColor3f Checkerboard::m_color1 = ShColor3f(0.0, 0.0, 0.0);ShColor3f Checkerboard::m_color2 = ShColor3f(1.0, 1.0, 1.0);Checkerboard cb_with_aa = Checkerboard(true);Checkerboard cb_without_aa = Checkerboard(false);