Thread: Problem with billboarding

I've tried getting billboarding to work, it seems easy enough, but no matter what I do it doesn't actually work. The bitmaps seem to somewhat turn with the camera but they are never actually completely perpendicular.

Here is what I have so far, what am I doing wrong? It's probably something incredibly obvious.

Code:

void	Meteor::CallDraw(){
	red = (int)rand()%255;
	green = (int)rand()%255;
	blue = (int)rand()%255;
	float scale = 10;
	float	MVMAT[16];
	glGetFloatv(GL_MODELVIEW_MATRIX, &MVMAT[0]);
	
	//FIXME: I don't know if I need the transpose or what is going on here
	Vector	up(MVMAT[0], MVMAT[1], MVMAT[2]);
	Vector	right(MVMAT[4], MVMAT[5], MVMAT[6]);
	
	glPushMatrix();
	glDisable(GL_LIGHTING);
	glEnable(GL_BLEND);	
	glBindTexture(GL_TEXTURE_2D, texture);		//THIS IS ACTUALLY THE PARTICLE TEXTURE, hmmm?
	glTranslatef(Position.x, Position.y, Position.z);
	glColor4ub(red, green, blue, transparency);
	glBegin(GL_QUADS);
	glTexCoord2f(0.0f, 0.0f);
glVertex3f(Position.x + (up.x + right.x) * -scale, Position.y + (up.y + right.y) * -scale, Position.z);
	glTexCoord2f(1.0f, 0.0f);
glVertex3f(Position.x + (-up.x + right.x) * scale, Position.y + (-up.y + right.y) * scale, Position.z); 
	glTexCoord2f(1.0f, 1.0f);
glVertex3f(Position.x + (up.x + right.x) * scale, Position.y + (up.y + right.y) * scale, Position.z);
	glTexCoord2f(0.0f, 1.0f);
glVertex3f(Position.x + (up.x + -right.x) * scale, Position.y + (up.y + -right.y) * scale, Position.z);
	glEnd();
	glDisable(GL_BLEND);
	glEnable(GL_LIGHTING);
	glPopMatrix();
}

I have tried using what the original model view matrix would be and what the transpose would be. i.e:
Vector up(MVMAT[0], MVMAT[1], MVMAT[2]);
Vector right(MVMAT[4], MVMAT[5], MVMAT[6]);

yes, that's what billboarding does. what's really supposed to happen is you're supposed to reverse the effects of the model view matrix by multiplying by its inverse. Instead (from ogl game programming) you can get the current up and right vectors from the modelview matrix, and use those to create the texture mapped quad. If you use components from the up and right vectors from the modelview matrix to set the vertices of the quad then the quad will always be facing the camera. I know I'm prolly doing something really stupid wrong. fuk

BILLBOARDING
UGG
BITMAP ALWAYS FACE VIEWER

you can't have a z component when you go into 2d ortho mode therefore that will not work, and this is actually the simplest method. i was hoping someone who had already done billboarding could check this out and correct me where i am wrong.

nein don quijote

do you have something that works that you could show me

try this....

Code:

Vector up(MVMAT[0], MVMAT[4], MVMAT[8]);
Vector right(MVMAT[1], MVMAT[5], MVMAT[9]);

// matrix might look like this

0  1  2   3
4  5  6   7
8  9 10 11