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/*
* 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) glVertexAttrib3fvARB(3, c)
#define VERTEX2F(x, y) glVertexAttrib2fARB(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;
glProgramLocalParameter4fARB(GL_VERTEX_PROGRAM_ARB, 30, x, y, z, 1);
glDisable(GL_VERTEX_PROGRAM_ARB);
glBegin(GL_POINTS);
glColor3f(1,1,1);
glVertex3f(x, y, z);
glEnd();
}
glEnable(GL_VERTEX_PROGRAM_ARB);
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 )
{
GLuint prognum;
GLint errno;
/*
* 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[] =
"!!ARBvp1.0\n"
"TEMP R1, R2, R3; "
"# Compute distance from vertex to gravity source\n"
"ADD R1, program.local[30], -vertex.position; # vector from vertex to gravity\n"
"DP3 R2, R1, R1; # dot product\n"
"RSQ R2, R2.x; # square root = distance\n"
"MUL R2, R2, program.local[31].xxxx; # scale by the gravity factor\n"
"# Displace vertex by gravity factor along R1 vector\n"
"MAD R3, R1, R2, vertex.position;\n"
"# Continue with typical modelview/projection\n"
"DP4 result.position.x, state.matrix.mvp.row[0], R3 ; # object x MVP -> clip\n"
"DP4 result.position.y, state.matrix.mvp.row[1], R3 ;\n"
"DP4 result.position.z, state.matrix.mvp.row[2], R3 ;\n"
"DP4 result.position.w, state.matrix.mvp.row[3], R3 ;\n"
"MOV result.color, vertex.attrib[3];\n # copy input color to output color\n"
"END";
if (!glutExtensionSupported("GL_ARB_vertex_program")) {
printf("Sorry, this program requires GL_ARB_vertex_program\n");
exit(1);
}
glGenProgramsARB(1, &prognum);
glBindProgramARB(GL_VERTEX_PROGRAM_ARB, prognum);
glProgramStringARB(GL_VERTEX_PROGRAM_ARB, GL_PROGRAM_FORMAT_ASCII_ARB,
strlen(prog), (const GLubyte *)prog);
errno = glGetError();
printf("glGetError = %d\n", errno);
if (errno != GL_NO_ERROR)
{
GLint errorpos;
glGetIntegerv(GL_PROGRAM_ERROR_POSITION_ARB, &errorpos);
printf("errorpos: %d\n", errorpos);
printf("%s\n", glGetString(GL_PROGRAM_ERROR_STRING_ARB));
}
/* Light position */
glProgramLocalParameter4fARB(GL_VERTEX_PROGRAM_ARB, 32, 2, 2, 4, 1);
/* Diffuse material color */
glProgramLocalParameter4fARB(GL_VERTEX_PROGRAM_ARB, 35, 0.25, 0, 0.25, 1);
/* Gravity strength */
glProgramLocalParameter4fARB(GL_VERTEX_PROGRAM_ARB, 31, .5, 0, 0, 0);
glEnable(GL_DEPTH_TEST);
glClearColor(0.3, 0.3, 0.3, 1);
glShadeModel(GL_FLAT);
glPointSize(3);
}
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;
}
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