satinshader.cpp

shrike is a utility application that acts as a testbed for shaders written in Sh

// 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
//////////////////////////////////////////////////////////////////////////////
// HACK: really a copy of SatinShader, with different defaults
#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 SatinShader : public Shader {
public:
  SatinShader();
  ~SatinShader();

  bool init();

  ShProgram vertex() { return vsh;}
  ShProgram fragment() { return fsh;}

  ShProgram vsh, fsh;

  static SatinShader instance;
};

SatinShader::SatinShader()
  : Shader("Homomorphic Factorization: Satin")
{
}

SatinShader::~SatinShader()
{
}

bool SatinShader::init()
{
  vsh = SH_BEGIN_PROGRAM("gpu:vertex") {
    ShInputPosition4f ipos;
    ShInputNormal3f inorm;
    ShInputTexCoord3f tc;  // ignored (for now)
    ShInputVector3f itan;
    
    ShOutputPosition4f opos; // Position in NDC
    ShOutputVector3f light; // direction to light (surface frame)
    ShOutputVector3f view;

    opos = Globals::mvp | ipos; // Compute NDC position
    ShNormal3f n = Globals::mv | inorm; // Compute view-space normal
    ShNormal3f t = Globals::mv | itan; // Compute view-space normal
    n = normalize(n);
    t = normalize(t);

    ShPoint3f posv = (Globals::mv | ipos)(0,1,2); // Compute view-space position
    ShVector3f lightv = normalize(Globals::lightPos - posv); // Compute light direction
    ShVector3f viewv = -normalize(posv); // Compute view vector

    // compute local surface frame (in view space)
    // ShVector3f t = normalize(itan - (itan|n)*n);
    ShVector3f s = normalize(cross(t,n));
    
    // project view and light vectors onto local surface frame
    view(0) = (t|viewv);
    view(1) = (s|viewv);
    view(2) = (n|viewv);

    light(0) = (t|lightv);
    light(1) = (s|lightv);
    light(2) = (n|lightv);  // if positive, is irradiance scale
  } SH_END;

  ShImage image;

  // TODO: should have array of available BRDFs with correction
  // factor for each, hidden uniforms (don't want user to play with
  // alpha, really), pulldown menu to select BRDFs from list,
  // settings for extra specularities, etc. etc.
  load_PNG(image, normalize_path(SHMEDIA_DIR "/brdfs/satin/satinp.png"));
  ShTable2D<ShColor3fub> ptex(image.width(), image.height());
  ptex.memory(image.memory());

  load_PNG(image, normalize_path(SHMEDIA_DIR "/brdfs/satin/satinq.png"));
  ShTable2D<ShColor3fub> qtex(image.width(), image.height());
  qtex.memory(image.memory());

  // HACK, satin doesn't have specular part, turned off by default
  load_PNG(image, normalize_path(SHMEDIA_DIR "/brdfs/specular.png"));
  ShTable2D<ShColor3fub> stex(image.width(), image.height());
  stex.memory(image.memory());

  // these scale factors are specific to satin
  ShColor3f SH_DECL(alpha) = ShColor3f(0.762367,0.762367,0.762367);
  ShAttrib1f SH_DECL(diffuse) = ShAttrib1f(1.0);
  diffuse.range(0.0,5.0);
  ShAttrib1f SH_DECL(specular) = ShAttrib1f(0.0);
  specular.range(0.0,1.0);
  ShColor3f SH_DECL(light_color) = ShColor3f(1.0,1.0,1.0);
  light_color.range(0.0,1.0);
  ShAttrib1f SH_DECL(light_power) = ShAttrib1f(1.0);
  light_power.range(0.0,100.0);

  
  fsh = SH_BEGIN_PROGRAM("gpu:fragment") {
    ShInputPosition4f posh;
    ShInputVector3f light;
    ShInputVector3f view;

    ShOutputColor3f result;

    // Normalize (theoretically not needed if compiler smart enough)
    light = normalize(light);
    view = normalize(view);

    // Incorporate diffuse scale, correction factor, and irradiance
    result = diffuse * alpha * pos(light(2));

    // compute half vector
    ShVector3f half = normalize(view + light); 

    // Theoretically not needed if use common subexpression elimination...
    ShTexCoord2f hu = parabolic_norm(half);
    ShTexCoord2f lu = parabolic_norm(light);
    ShTexCoord2f vu = parabolic_norm(view);

    // TODO: SHOULD use automatic projective normalization in texture lookup...
    // and/or parabolic texture type instead.
    result *= ptex(lu);
    result *= qtex(hu);
    result *= ptex(vu);

    // Add in specular term (also represented using parabolic map)
    result += specular * stex(hu) * pos(light(2));

    // Take into account light power and colour
    result *= light_power * light_color;
  } SH_END;
  return true;
}

// TODO: above code actually results in redundant normalization calls
// to light (it is normalized in both irradiance and in parabolic_norm).
// Rather than "fix" this code, this shader should be used as a test
// case (and an example) for automatic common subexpression elimination.
// Note that repeated normalization can be avoided with unit flags,
// so inserting the commented-out code block for normalization fixes
// the problem from an efficiency standpoint... even though vectors
// are normalized more than once in the code, the final assembly should
// only do it once.

SatinShader SatinShader::instance = SatinShader();