demo of GL_SGIX_shadow

1 files changed, 393 insertions, 0 deletions

diff --git a/progs/demos/shadowtex.c b/progs/demos/shadowtex.c
new file mode 100644
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+++ b/progs/demos/shadowtex.c
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+/* $Id: shadowtex.c,v 1.1 2001/02/20 16:43:50 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);
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_SGIX, GL_TRUE);
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_OPERATOR_SGIX,
+                   GL_TEXTURE_LEQUAL_R_SGIX);
+
+   if (glutExtensionSupported("GL_SGIX_shadow_ambient"))
+      glTexParameterf(GL_TEXTURE_2D, GL_SHADOW_AMBIENT_SGIX, 0.3);
+
+   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;
+}