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View Full Version : Last Try: Texture with alpha channel



uwi2k2
01-15-2012, 04:15 AM
hi there,

i am trying this for weeks now, and finally i have a code that should show a plane with a texture that has transparent parts, but it does not...
there are 2 planes and as one is behind the other i should see it through the 'hols' ( alpha 0 parts ) of the one in front... but nothing happens...

i will post the complete code here so you may test it on your system and tell me what i am doing wrong.

Thanx a lot for any ideea, if i cant get thisone done i will give up on programming opengl ....




#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

/* Create checkerboard texture */
#define checkImageWidth 64
#define checkImageHeight 64
static GLubyte checkImage[checkImageHeight][checkImageWidth][4];

#ifdef GL_VERSION_1_1
static GLuint texName;
#endif

void makeCheckImage(void)
{
int i, j, c;

for (i = 0; i < checkImageHeight; i++) {
for (j = 0; j < checkImageWidth; j++) {
c = ((((i&amp;0x8)==0)^((j&amp;0x8))==0))*255;
checkImage[i][j][0] = (GLubyte) c;
checkImage[i][j][1] = (GLubyte) c;
checkImage[i][j][2] = (GLubyte) c;
checkImage[i][j][3] = (GLubyte) 128;
}
}
}

void init(void)
{
glClearColor (0.0, 0.0, 0.0, 0.0);
glShadeModel(GL_FLAT);
glEnable(GL_DEPTH_TEST);

makeCheckImage();
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

#ifdef GL_VERSION_1_1
glGenTextures(1, &amp;texName);
glBindTexture(GL_TEXTURE_2D, texName);
#endif

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
#ifdef GL_VERSION_1_1
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth, checkImageHeight,
0, GL_RGBA, GL_UNSIGNED_BYTE, checkImage);
#else
glTexImage2D(GL_TEXTURE_2D, 0, 4, checkImageWidth, checkImageHeight,
0, GL_RGBA, GL_UNSIGNED_BYTE, checkImage);
#endif
}

void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
#ifdef GL_VERSION_1_1
glBindTexture(GL_TEXTURE_2D, texName);
#endif

glBegin(GL_QUADS);

glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, 0.0);
glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, 0.0);
glTexCoord2f(1.0, 1.0); glVertex3f(1.41421, 1.0, -2.41421);
glTexCoord2f(1.0, 0.0); glVertex3f(1.41421, -1.0, -2.41421);


glTexCoord2f(0.0, 0.0); glVertex3f(-2.0, -1.0, 0.0);
glTexCoord2f(0.0, 1.0); glVertex3f(-2.0, 1.0, 0.0);
glTexCoord2f(1.0, 1.0); glVertex3f(0.0, 1.0, 0.0);
glTexCoord2f(1.0, 0.0); glVertex3f(0.0, -1.0, 0.0);


glEnd();
glFlush();
glDisable(GL_TEXTURE_2D);
}

void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, (GLfloat) w/(GLfloat) h, 1.0, 30.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -3.6);
}

void keyboard (unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(0);
break;
default:
break;
}
}

int main(int argc, char** argv)
{
glutInit(&amp;argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA | GLUT_DEPTH);
glutInitWindowSize(250, 250);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}

mbentrup
01-15-2012, 12:12 PM
Add this to your display function:



glEnable(GL_BLEND);
glBlendFunc(GL_ALPHA, GL_ONE_MINUS_SRC_ALPHA);