warp a quadmesh with a gravitational source via vertex program

diff --git a/progs/tests/vpwarpmesh.c b/progs/tests/vpwarpmesh.c
new file mode 100644 (file)
index 0000000..166ef9c
--- /dev/null
+++ b/progs/tests/vpwarpmesh.c
@@ -0,0 +1,236 @@
+/*
+ * Warp a triangle mesh with a vertex program.
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#define GL_GLEXT_PROTOTYPES
+#include <GL/glut.h>
+
+static float Xrot = -60.0, Yrot = 0.0, Zrot = 0.0;
+static GLboolean Anim = GL_TRUE;
+static GLfloat Phi = 0.0;
+
+
+static void Idle( void )
+{
+   Phi += 0.01;
+   glutPostRedisplay();
+}
+
+
+static void DrawMesh( int rows, int cols )
+{
+   static const GLfloat colorA[3] = { 0, 1, 0 };
+   static const GLfloat colorB[3] = { 0, 0, 1 };
+   const float dx = 2.0 / (cols - 1);
+   const float dy = 2.0 / (rows - 1);
+   float x, y;
+   int i, j;
+
+#if 1
+#define COLOR3FV(c)     glVertexAttrib3fvNV(3, c)
+#define VERTEX2F(x, y)  glVertexAttrib2fNV(0, x, y)
+#else
+#define COLOR3FV(c)     glColor3fv(c)
+#define VERTEX2F(x, y)  glVertex2f(x, y)
+#endif
+
+   y = -1.0;
+   for (i = 0; i < rows - 1; i++) {
+      glBegin(GL_QUAD_STRIP);
+      x = -1.0;
+      for (j = 0; j < cols; j++) {
+         if ((i + j) & 1)
+            COLOR3FV(colorA);
+         else
+            COLOR3FV(colorB);
+         VERTEX2F(x, y);
+         VERTEX2F(x, y + dy);
+         x += dx;
+      }
+      glEnd();
+      y += dy;
+   }
+}
+
+
+static void Display( void )
+{
+   glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
+
+   glPushMatrix();
+      glRotatef(Xrot, 1, 0, 0);
+      glRotatef(Yrot, 0, 1, 0);
+      glRotatef(Zrot, 0, 0, 1);
+
+      /* Position the gravity source */
+      {
+         GLfloat x, y, z, r = 0.5;
+         x = r * cos(Phi);
+         y = r * sin(Phi);
+         z = 1.0;
+         glProgramParameter4fNV(GL_VERTEX_PROGRAM_NV, 30, x, y, z, 1);
+         glDisable(GL_VERTEX_PROGRAM_NV);
+         glBegin(GL_POINTS);
+         glColor3f(1,1,1);
+         glVertex3f(x, y, z);
+         glEnd();
+      }
+
+      glEnable(GL_VERTEX_PROGRAM_NV);
+      DrawMesh(8, 8);
+   glPopMatrix();
+
+   glutSwapBuffers();
+}
+
+
+static void Reshape( int width, int height )
+{
+   float ar = (float) width / (float) height;
+   glViewport( 0, 0, width, height );
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glFrustum( -1.0 * ar, 1.0 * ar, -1.0, 1.0, 5.0, 25.0 );
+   glMatrixMode( GL_MODELVIEW );
+   glLoadIdentity();
+   glTranslatef( 0.0, 0.0, -12.0 );
+   glScalef(2, 2, 2);
+}
+
+
+static void Key( unsigned char key, int x, int y )
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+      case 'a':
+         Anim = !Anim;
+         if (Anim)
+            glutIdleFunc(Idle);
+         else
+            glutIdleFunc(NULL);
+         break;
+      case 'p':
+         Phi += 0.2;
+         break;
+      case 'z':
+         Zrot -= 5.0;
+         break;
+      case 'Z':
+         Zrot += 5.0;
+         break;
+      case 27:
+         exit(0);
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void SpecialKey( int key, int x, int y )
+{
+   const GLfloat step = 3.0;
+   (void) x;
+   (void) y;
+   switch (key) {
+      case GLUT_KEY_UP:
+         Xrot -= step;
+         break;
+      case GLUT_KEY_DOWN:
+         Xrot += step;
+         break;
+      case GLUT_KEY_LEFT:
+         Yrot -= step;
+         break;
+      case GLUT_KEY_RIGHT:
+         Yrot += step;
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void Init( void )
+{
+   /*
+    * c[0..3] = modelview matrix
+    * c[4..7] = inverse modelview matrix
+    * c[30] = gravity source location
+    * c[31] = gravity source strength
+    * c[32] = light pos
+    * c[35] = diffuse color
+    */
+   static const char prog[] = 
+      "!!VP1.0\n"
+
+      "# Compute distance from vertex to gravity source\n"
+      "ADD   R1, c[30], -v[OPOS]; # vector from vertex to gravity\n"
+      "DP3   R2, R1, R1;          # dot product\n"
+      "RSQ   R2, R2.x;            # square root = distance\n"
+      "MUL   R2, R2, c[31].xxxx;  # scale by the gravity factor\n"
+
+      "# Displace vertex by gravity factor along R1 vector\n"
+      "MAD   R3, R1, R2, v[OPOS];\n"
+
+      "# Continue with typical modelview/projection\n"
+      "DP4   o[HPOS].x, c[0], R3 ;     # object x MVP -> clip\n"
+      "DP4   o[HPOS].y, c[1], R3 ;\n"
+      "DP4   o[HPOS].z, c[2], R3 ;\n"
+      "DP4   o[HPOS].w, c[3], R3 ;\n"
+
+      "MOV   o[COL0], v[COL0];\n       # copy input color to output color\n"
+
+      "END";
+
+   if (!glutExtensionSupported("GL_NV_vertex_program")) {
+      printf("Sorry, this program requires GL_NV_vertex_program");
+      exit(1);
+   }
+
+   glLoadProgramNV(GL_VERTEX_PROGRAM_NV, 1,
+                   strlen(prog), (const GLubyte *) prog);
+   assert(glIsProgramNV(1));
+   glBindProgramNV(GL_VERTEX_PROGRAM_NV, 1);
+
+   /* Load the program registers */
+   glTrackMatrixNV(GL_VERTEX_PROGRAM_NV, 0, GL_MODELVIEW_PROJECTION_NV, GL_IDENTITY_NV);
+   glTrackMatrixNV(GL_VERTEX_PROGRAM_NV, 4, GL_MODELVIEW, GL_INVERSE_TRANSPOSE_NV);
+
+   /* Light position */
+   glProgramParameter4fNV(GL_VERTEX_PROGRAM_NV, 32, 2, 2, 4, 1);
+   /* Diffuse material color */
+   glProgramParameter4fNV(GL_VERTEX_PROGRAM_NV, 35, 0.25, 0, 0.25, 1);
+
+   /* Gravity strength */
+   glProgramParameter4fNV(GL_VERTEX_PROGRAM_NV, 31, .5, 0, 0, 0);
+
+   glEnable(GL_DEPTH_TEST);
+   glClearColor(0.3, 0.3, 0.3, 1);
+   glShadeModel(GL_FLAT);
+   glPointSize(3);
+   printf("glGetError = %d\n", (int) glGetError());
+}
+
+
+int main( int argc, char *argv[] )
+{
+   glutInit( &argc, argv );
+   glutInitWindowPosition( 0, 0 );
+   glutInitWindowSize( 250, 250 );
+   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
+   glutCreateWindow(argv[0]);
+   glutReshapeFunc( Reshape );
+   glutKeyboardFunc( Key );
+   glutSpecialFunc( SpecialKey );
+   glutDisplayFunc( Display );
+   if (Anim)
+      glutIdleFunc(Idle);
+   Init();
+   glutMainLoop();
+   return 0;
+}