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better test of point attenuation

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This commit is contained in:
Brian 2007-11-23 16:19:25 -07:00
parent 88b067cb04
commit be1fa5b3d7
1 changed files with 34 additions and 24 deletions
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58
progs/trivial/point-param.c
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@ -23,15 +23,13 @@
*/
#define GL_GLEXT_PROTOTYPES
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <GL/glut.h>
#define CI_OFFSET_1 16
#define CI_OFFSET_2 32
GLenum doubleBuffer;
@ -41,53 +39,63 @@ static void Init(void)
fprintf(stderr, "GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
fprintf(stderr, "GL_VENDOR = %s\n", (char *) glGetString(GL_VENDOR));
glClearColor(0.0, 0.0, 1.0, 0.0);
glClearColor(0.0, 0.0, 1.0, 0.0);
}
static void Reshape(int width, int height)
{
glViewport(0, 0, (GLint)width, (GLint)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0);
glOrtho(-1.0, 1.0, -1.0, 1.0, 0, 100.0);
glMatrixMode(GL_MODELVIEW);
}
static void Key(unsigned char key, int x, int y)
{
switch (key) {
case 27:
case 27:
exit(1);
default:
default:
return;
}
glutPostRedisplay();
}
static float
expected(float z, float size, const float atten[3])
{
float dist = fabs(z);
const GLfloat q = atten[0] + dist * (atten[1] + dist * atten[2]);
const GLfloat a = sqrt(1.0 / q);
return size * a;
}
static void Draw(void)
{
static GLfloat theQuad[3] = { 0.25, 0.0, 1/60.0 };
static GLfloat atten[3] = { 0.0, 0.1, .01 };
float size = 40.0;
int i;
glClear(GL_COLOR_BUFFER_BIT);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glPointSize(8.0);
glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, theQuad);
glPointSize(size);
glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION_ARB, atten);
glBegin(GL_POINTS);
glColor3f(1,0,0);
glVertex3f( 0.9, -0.9, -30.0);
glColor3f(1,1,0);
glVertex3f( 0.9, 0.9, -30.0);
glColor3f(1,0,1);
glVertex3f(-0.9, 0.9, -30.0);
glColor3f(0,1,1);
glVertex3f(-0.9, -0.9, -30.0);
printf("Expected point sizes:\n");
glBegin(GL_POINTS);
for (i = 0; i < 5; i++) {
float x = -0.8 + i * 0.4;
float z = -i * 20 - 10;
glVertex3f( x, 0.0, z);
printf(" %f\n", expected(z, size, atten));
}
glEnd();
glFlush();
@ -97,6 +105,7 @@ static void Draw(void)
}
}
static GLenum Args(int argc, char **argv)
{
GLint i;
@ -116,6 +125,7 @@ static GLenum Args(int argc, char **argv)
return GL_TRUE;
}
int main(int argc, char **argv)
{
GLenum type;
@ -132,7 +142,7 @@ int main(int argc, char **argv)
type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
glutInitDisplayMode(type);
if (glutCreateWindow("First Tri") == GL_FALSE) {
if (glutCreateWindow(argv[0]) == GL_FALSE) {
exit(1);
}
@ -142,5 +152,5 @@ int main(int argc, char **argv)
glutKeyboardFunc(Key);
glutDisplayFunc(Draw);
glutMainLoop();
return 0;
return 0;
}