/* $Id: shadowtex.c,v 1.2 2001/02/20 17:06:35 brianp Exp $ */

/*
 * Shadow demo using the GL_SGIX_depth_texture, GL_SGIX_shadow and
 * GL_SGIX_shadow_ambient extensions.
 *
 * Brian Paul
 * 19 Feb 2001
 *
 * Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include "../util/showbuffer.c"


#define DEG_TO_RAD (3.14159 / 180.0)

static GLint WindowWidth = 450, WindowHeight = 300;
static GLfloat Xrot = 15, Yrot = 0, Zrot = 0;

static GLfloat Red[4] = {1, 0, 0, 1};
static GLfloat Green[4] = {0, 1, 0, 1};
static GLfloat Blue[4] = {0, 0, 1, 1};
static GLfloat Yellow[4] = {1, 1, 0, 1};

static GLfloat LightDist = 10;
static GLfloat LightLatitude = 45.0;
static GLfloat LightLongitude = 45.0;
static GLfloat LightPos[4];
static GLfloat SpotDir[3];
static GLfloat SpotAngle = 40.0 * DEG_TO_RAD;
static GLfloat ShadowNear = 4.0, ShadowFar = 24.0;
static GLint ShadowTexWidth = 256, ShadowTexHeight = 256;

static GLboolean ShowDepth = GL_FALSE;

static GLfloat ShadowImage[256*256];

static GLfloat Bias = -0.06;

static GLboolean Anim = GL_TRUE;


static void
DrawScene(void)
{
   GLfloat k = 6;
   /* sphere */
   glPushMatrix();
   glTranslatef(1.6, 2.2, 2.7);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Green);
   glColor4fv(Green);
   glutSolidSphere(1.5, 15, 15);
   glPopMatrix();
   /* dodecahedron */
   glPushMatrix();
   glTranslatef(-2.0, 1.2, 2.1);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Red);
   glColor4fv(Red);
   glutSolidDodecahedron();
   glPopMatrix();
   /* icosahedron */
   glPushMatrix();
   glTranslatef(-0.6, 1.3, -0.5);
   glScalef(1.5, 1.5, 1.5);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Yellow);
   glColor4fv(Red);
   glutSolidIcosahedron();
   glPopMatrix();
   /* a plane */
   glPushMatrix();
   glTranslatef(0, -1.1, 0);
   glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, Blue);
   glColor4fv(Blue);
   glNormal3f(0, 1, 0);
   glBegin(GL_POLYGON);
   glVertex3f(-k, 0, -k);
   glVertex3f( k, 0, -k);
   glVertex3f( k, 0,  k);
   glVertex3f(-k, 0,  k);
   glEnd();
   glPopMatrix();
}


/*
 * Load the GL_TEXTURE matrix with the projection from the light
 * source's point of view.
 */
static void
ShadowMatrix(const GLfloat lightPos[4], const GLfloat spotDir[3],
             GLfloat spotAngle, GLfloat shadowNear, GLfloat shadowFar)
{
   GLfloat d;
   
   glMatrixMode(GL_TEXTURE);
   glLoadIdentity();
   glTranslatef(0.5, 0.5, 0.5 + Bias);
   glScalef(0.5, 0.5, 0.5);
   d = shadowNear * tan(spotAngle);
   glFrustum(-d, d, -d, d, shadowNear, shadowFar);
   gluLookAt(lightPos[0], lightPos[1], lightPos[2],
             lightPos[0] + spotDir[0],
             lightPos[1] + spotDir[1],
             lightPos[2] + spotDir[2],
             0, 1, 0);
   glMatrixMode(GL_MODELVIEW);
}


static void
EnableTexgen(void)
{
   /* texgen so that texcoord = vertex coord */
   static GLfloat sPlane[4] = { 1, 0, 0, 0 };
   static GLfloat tPlane[4] = { 0, 1, 0, 0 };
   static GLfloat rPlane[4] = { 0, 0, 1, 0 };
   static GLfloat qPlane[4] = { 0, 0, 0, 1 };

   glTexGenfv(GL_S, GL_EYE_PLANE, sPlane);
   glTexGenfv(GL_T, GL_EYE_PLANE, tPlane);
   glTexGenfv(GL_R, GL_EYE_PLANE, rPlane);
   glTexGenfv(GL_Q, GL_EYE_PLANE, qPlane);
   glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);
   glTexGeni(GL_Q, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR);

   glEnable(GL_TEXTURE_GEN_S);
   glEnable(GL_TEXTURE_GEN_T);
   glEnable(GL_TEXTURE_GEN_R);
   glEnable(GL_TEXTURE_GEN_Q);
}


static void
DisableTexgen(void)
{
   glDisable(GL_TEXTURE_GEN_S);
   glDisable(GL_TEXTURE_GEN_T);
   glDisable(GL_TEXTURE_GEN_R);
   glDisable(GL_TEXTURE_GEN_Q);
}


static void
ComputeLightPos(GLfloat dist, GLfloat latitude, GLfloat longitude,
                GLfloat pos[4], GLfloat dir[3])
{
   pos[0] = dist * sin(longitude * DEG_TO_RAD);
   pos[1] = dist * sin(latitude * DEG_TO_RAD);
   pos[2] = dist * cos(latitude * DEG_TO_RAD) * cos(longitude * DEG_TO_RAD);
   pos[3] = 1;
   dir[0] = -pos[0];
   dir[1] = -pos[1];
   dir[2] = -pos[2];
}


static void
Display(void)
{
   GLfloat ar = (GLfloat) WindowWidth / (GLfloat) WindowHeight;
   GLfloat d;

   ComputeLightPos(LightDist, LightLatitude, LightLongitude,
                   LightPos, SpotDir);
   /*
    * Step 1: render scene from point of view of the light source
    */
   /* compute frustum to enclose spot light cone */
   d = ShadowNear * tan(SpotAngle);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-d, d, -d, d, ShadowNear, ShadowFar);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt(LightPos[0], LightPos[1], LightPos[2], /* from */
             0, 0, 0, /* target */
             0, 1, 0); /* up */

   glViewport(0, 0, ShadowTexWidth, ShadowTexHeight);
   glClear(GL_DEPTH_BUFFER_BIT);
   DrawScene();

   /*
    * Step 2: copy depth buffer into texture map
    */
   glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT,
                    0, 0, ShadowTexWidth, ShadowTexHeight, 0);

   /*
    * Step 3: render scene from point of view of the camera
    */
   glViewport(0, 0, WindowWidth, WindowHeight);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-ar, ar, -1.0, 1.0, 4.0, 50.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   glTranslatef(0.0, 0.0, -22.0);
   glRotatef(Xrot, 1, 0, 0);
   glRotatef(Yrot, 0, 1, 0);
   glRotatef(Zrot, 0, 0, 1);
   if (ShowDepth) {
      ShowDepthBuffer(WindowWidth, WindowHeight, 1, 0);
   }
   else {
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      glLightfv(GL_LIGHT0, GL_POSITION, LightPos);
      glEnable(GL_TEXTURE_2D);
      ShadowMatrix(LightPos, SpotDir, SpotAngle, ShadowNear, ShadowFar);
      EnableTexgen();
      DrawScene();
      DisableTexgen();
      glDisable(GL_TEXTURE_2D);
   }

   glutSwapBuffers();
}


static void
Reshape(int width, int height)
{
   WindowWidth = width;
   WindowHeight = height;
}


static void
Idle(void)
{
   Yrot += 5.0;
   /*LightLongitude -= 5.0;*/
   glutPostRedisplay();
}


static void
Key(unsigned char key, int x, int y)
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case 'a':
         Anim = !Anim;
         if (Anim)
            glutIdleFunc(Idle);
         else
            glutIdleFunc(NULL);
         break;
      case 'b':
         Bias -= 0.01;
         break;
      case 'B':
         Bias += 0.01;
         break;
      case 'd':
         ShowDepth = !ShowDepth;
         break;
      case 'z':
         Zrot -= step;
         break;
      case 'Z':
         Zrot += step;
         break;
      case 27:
         exit(0);
         break;
   }
   glutPostRedisplay();
   printf("Bias %g\n", Bias);
}


static void
SpecialKey(int key, int x, int y)
{
   const GLfloat step = 3.0;
   const int mod = glutGetModifiers();
   (void) x;
   (void) y;
   switch (key) {
      case GLUT_KEY_UP:
         if (mod)
            LightLatitude += step;
         else
            Xrot += step;
         break;
      case GLUT_KEY_DOWN:
         if (mod)
            LightLatitude -= step;
         else
            Xrot -= step;
         break;
      case GLUT_KEY_LEFT:
         if (mod)
            LightLongitude += step;
         else
            Yrot += step;
         break;
      case GLUT_KEY_RIGHT:
         if (mod)
            LightLongitude -= step;
         else
            Yrot -= step;
         break;
   }
   glutPostRedisplay();
}


static void
Init(void)
{
   if (!glutExtensionSupported("GL_SGIX_depth_texture") ||
       !glutExtensionSupported("GL_SGIX_shadow")) {
      printf("Sorry, this demo requires the GL_SGIX_depth_texture and GL_SGIX_shadow extensions\n");
      exit(1);
   }

   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
#ifdef GL_SGIX_shadow
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_SGIX, GL_TRUE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_OPERATOR_SGIX,
                   GL_TEXTURE_LEQUAL_R_SGIX);
#endif
#ifdef GL_SGIX_shadow_ambient
   if (glutExtensionSupported("GL_SGIX_shadow_ambient"))
      glTexParameterf(GL_TEXTURE_2D, GL_SHADOW_AMBIENT_SGIX, 0.3);
#endif

   glEnable(GL_DEPTH_TEST);
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
}


static void
PrintHelp(void)
{
   printf("Keys:\n");
   printf("  a = toggle animation\n");
   printf("  d = toggle display of depth texture\n");
   printf("  b/B = decrease/increase shadow map Z bias\n");
   printf("  cursor keys = rotate scene\n");
   printf("  <shift> + cursor keys = rotate light source\n");
}


int
main(int argc, char *argv[])
{
   glutInit(&argc, argv);
   glutInitWindowPosition(0, 0);
   glutInitWindowSize(WindowWidth, WindowHeight);
   glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
   glutCreateWindow(argv[0]);
   glutReshapeFunc(Reshape);
   glutKeyboardFunc(Key);
   glutSpecialFunc(SpecialKey);
   glutDisplayFunc(Display);
   if (Anim)
      glutIdleFunc(Idle);
   Init();
   PrintHelp();
   glutMainLoop();
   return 0;
}