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Code Issues Projects Releases Packages Wiki Activity Actions 2

draw a tristrip ring instead of a single quad

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This commit is contained in:
Brian Paul 2008-08-15 17:01:35 -06:00
parent 37f452096b
commit 1b39b92e6d
1 changed files with 38 additions and 14 deletions
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52
progs/glsl/twoside.c
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@ -28,7 +28,7 @@ static GLuint program;
static GLint win = 0;
static GLboolean anim = 0*GL_TRUE;
static GLboolean DetermineInFragProg = GL_TRUE;
static GLfloat Yrot = 0.0f;
static GLfloat Xrot = 30.0f;
static GLint u_fragface;
static GLenum FrontWinding = GL_CCW;
static int prevTime = 0;
@ -41,7 +41,8 @@ static const GLfloat Green[4] = {0, 1, 0, 0};
static void
Redisplay(void)
{
float xmin = -1, xmax = 1, ymin = -1, ymax = 1;
int i;
float radius = 2;
glFrontFace(FrontWinding);
@ -54,18 +55,22 @@ Redisplay(void)
glEnable(GL_VERTEX_PROGRAM_TWO_SIDE);
}
glClear(GL_COLOR_BUFFER_BIT);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glPushMatrix();
glRotatef(Yrot, 0, 1, 0);
glRotatef(Xrot, 1, 0, 0);
glBegin(GL_POLYGON);
/* Draw a tristrip ring */
glBegin(GL_TRIANGLE_STRIP);
glColor4fv(Red);
glSecondaryColor3fv_func(Green);
glVertex2f(xmin, ymin);
glVertex2f(xmax, ymin);
glVertex2f(xmax, ymax);
glVertex2f(xmin, ymax);
for (i = 0; i < 20; i++) {
float a = i / 19.0 * M_PI * 2.0;
float x = radius * cos(a);
float y = radius * sin(a);
glVertex3f(x, -1, y);
glVertex3f(x, +1, y);
}
glEnd();
glPopMatrix();
@ -86,7 +91,7 @@ Idle(void)
}
prevTime = curTime;
Yrot += dt * 0.1;
Xrot += dt * 0.1;
glutPostRedisplay();
}
@ -98,7 +103,7 @@ Reshape(int width, int height)
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-ar, ar, -1, 1, 5, 15);
glFrustum(-ar, ar, -1, 1, 3, 25);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0, 0, -10);
@ -141,12 +146,16 @@ Key(unsigned char key, int x, int y)
DetermineInFragProg = GL_FALSE;
break;
case 'r':
Yrot = 0;
/* reset */
Xrot = 30;
anim = 0;
glutIdleFunc(NULL);
break;
case 's':
Yrot += 5;
Xrot += 5;
break;
case 'S':
Xrot -= 5;
break;
case 'w':
if (FrontWinding == GL_CCW) {
@ -173,12 +182,24 @@ Init(void)
static const char *fragShaderText =
"uniform bool fragface; \n"
"void main() { \n"
#if 0
" if (!fragface || gl_FrontFacing) { \n"
" gl_FragColor = gl_Color; \n"
" } \n"
" else { \n"
" gl_FragColor = 0.8 * gl_SecondaryColor; \n"
" } \n"
#else
" bool f = gl_FrontFacing; \n"
" if (f) { \n"
" gl_FragColor = vec4(1.0, 0.0, 0.0, 0.0); \n"
" } \n"
" else { \n"
" gl_FragColor = vec4(0.0, 1.0, 0.0, 0.0); \n"
" } \n"
" //float g = float(gl_FrontFacing) * 0.5 + 0.5; \n"
" //gl_FragColor = vec4(g); \n"
#endif
"} \n";
static const char *vertShaderText =
"uniform bool fragface; \n"
@ -218,6 +239,8 @@ Init(void)
assert(glIsProgram_func(program));
assert(glIsShader_func(fragShader));
assert(glIsShader_func(vertShader));
glEnable(GL_DEPTH_TEST);
}
@ -246,6 +269,7 @@ Usage(void)
printf(" a - toggle animation\n");
printf(" s - step rotation\n");
printf(" w - toggle CW, CCW front-face winding\n");
printf("NOTE: red = front face, green = back face.\n");
}
@ -255,7 +279,7 @@ main(int argc, char *argv[])
glutInit(&argc, argv);
glutInitWindowPosition( 0, 0);
glutInitWindowSize(WinWidth, WinHeight);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
win = glutCreateWindow(argv[0]);
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);