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/*
* Test minification vs. magnification filtering.
* Draw two quads with different filtering modes:
*
* +--------------------------+ +--------------------------+
* | MagFilter = GL_LINEAR | | MagFilter = GL_LINEAR |
* | MinFilter = GL_LINEAR | | MinFilter = GL_NEAREST |
* +--------------------------+ +--------------------------+
*
* They should look different when the quad is smaller than the level 0
* texture size (when minifying).
*/
#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <GL/glut.h>
static GLint Width = 1000, Height = 500;
static GLint TexWidth = 256, TexHeight = 256;
static GLfloat Zpos = 5;
static GLboolean MipMap = 0*GL_TRUE;
static GLboolean LinearFilter = GL_TRUE;
static void
redraw(void)
{
GLfloat w = 1.0;
GLfloat h = 1.0;
glClear( GL_COLOR_BUFFER_BIT );
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glPushMatrix();
glTranslatef(-1.5, 0, -Zpos);
glBegin(GL_POLYGON);
glTexCoord2f(0, 0); glVertex2f(-w, -h);
glTexCoord2f(1, 0); glVertex2f( w, -h);
glTexCoord2f(1, 1); glVertex2f( w, h);
glTexCoord2f(0, 1); glVertex2f(-w, h);
glEnd();
glPopMatrix();
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glPushMatrix();
glTranslatef(1.5, 0, -Zpos);
glBegin(GL_POLYGON);
glTexCoord2f(0, 0); glVertex2f(-w, -h);
glTexCoord2f(1, 0); glVertex2f( w, -h);
glTexCoord2f(1, 1); glVertex2f( w, h);
glTexCoord2f(0, 1); glVertex2f(-w, h);
glEnd();
glPopMatrix();
glutSwapBuffers();
}
static void
init(void)
{
GLubyte color[10][4] = {
{ 0, 0, 0, 0 },
{ 1, 0, 0, 0 },
{ 0, 1, 0, 0 },
{ 0, 0, 1, 0 },
{ 0, 1, 1, 0 },
{ 1, 0, 1, 0 },
{ 1, 1, 0, 0 },
{ 1, 0, 0, 0 },
{ 0, 1, 0, 0 },
{ 0, 0, 1, 0 }
};
GLubyte *texImage;
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
printf("Left quad should be linear filtered and right should be nearest filtered.\n");
printf("Press z/Z to change quad distance.\n");
texImage = (GLubyte*) malloc(4 * TexWidth * TexHeight * sizeof(GLubyte));
assert(texImage);
{
GLint level = 0;
GLint w = TexWidth, h = TexHeight;
while (1) {
int i, j;
for (i = 0; i < h; i++) {
for (j = 0;j < w; j++) {
if (w==1 || h==1 || (((i / 2) ^ (j / 2)) & 1)) {
/*if (j < i) {*/
texImage[(i*w+j) * 4 + 0] = 255;
texImage[(i*w+j) * 4 + 1] = 255;
texImage[(i*w+j) * 4 + 2] = 255;
texImage[(i*w+j) * 4 + 3] = 255;
}
else {
texImage[(i*w+j) * 4 + 0] = color[level][0] * 255;
texImage[(i*w+j) * 4 + 1] = color[level][1] * 255;
texImage[(i*w+j) * 4 + 2] = color[level][2] * 255;
texImage[(i*w+j) * 4 + 3] = color[level][3] * 255;
}
}
}
glTexImage2D(GL_TEXTURE_2D, level, GL_RGBA8, w, h, 0,
GL_RGBA, GL_UNSIGNED_BYTE, texImage);
printf("Texture level %d: %d x %d\n", level, w, h);
if (!MipMap)
break;
if (w == 1 && h == 1)
break;
if (w > 1)
w /= 2;
if (h > 1)
h /= 2;
level++;
}
}
free(texImage);
glClearColor(0.25, 0.25, 0.25, 1.0);
glEnable(GL_TEXTURE_2D);
glViewport(0, 0, Width, Height);
}
static void
Reshape(int width, int height)
{
float ar = (float) width /height;
Width = width;
Height = height;
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-ar, ar, -1.0, 1.0, 5.0, 2500.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -15.0);
}
static void
Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
switch (key) {
case 'z':
Zpos--;
break;
case 'Z':
Zpos++;
break;
case 'f':
LinearFilter = !LinearFilter;
break;
case 27:
exit(0);
break;
}
glutPostRedisplay();
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowPosition(0, 0);
glutInitWindowSize(Width, Height);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow(argv[0]);
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(redraw);
init();
glutMainLoop();
return 0;
}
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