#include?

#include?“gl\glut.h“
#include?

#include?“maths.h“


/*-----------------------------------------------------------------
The?objects?motion?is?restricted?to?a?rotation?on?a?predefined?axis
The?function?bellow?does?cylindrical?billboarding?on?the?Y?axis?i.e.
the?object?will?be?able?to?rotate?on?the?Y?axis?only.
-----------------------------------------------------------------*/

void?l3dBillboardLocalToWorld（float?*cam?float?*worldPos）?{
	float?modelview[16];

	glGetFloatv（GL_MODELVIEW_MATRIX?modelview）;

//?The?local?origin‘s?position?in?world?coordinates
	worldPos[0]?=?cam[0]?+?modelview[12]*modelview[0]?+?modelview[13]?*?modelview[1]?+?modelview[14]?*?modelview[2];
	worldPos[1]?=?cam[1]?+?modelview[12]*modelview[4]?+?modelview[13]?*?modelview[5]?+?modelview[14]?*?modelview[6];
	worldPos[2]?=?cam[2]?+?modelview[12]*modelview[8]?+?modelview[13]?*?modelview[9]?+?modelview[14]?*?modelview[10];
}


/*-----------------------------------------------------------------
The?objects?motion?is?restricted?to?a?rotation?on?a?predefined?axis
The?function?bellow?does?cylindrical?billboarding?on?the?Y?axis?i.e.
the?object?will?be?able?to?rotate?on?the?Y?axis?only.
-----------------------------------------------------------------*/
void?l3dBillboardCylindricalBegin（float?*cam?float?*worldPos）?{

	float?lookAt[3]={001}objToCamProj[3]upAux[3]angleCosine;

//?objToCamProj?is?the?vector?in?world?coordinates?from?the?local?origin?to?the?camera
//?projected?in?the?XZ?plane
	objToCamProj[0]?=?cam[0]?-?worldPos[0]?;
	objToCamProj[1]?=?0;
	objToCamProj[2]?=?cam[2]?-?worldPos[2]?;


//?normalize?both?vectors?to?get?the?cosine?directly?afterwards
	mathsNormalize（objToCamProj）;

//?easy?fix?to?determine?wether?the?angle?is?negative?or?positive
//?for?positive?angles?upAux?will?be?a?vector?pointing?in?the?
//?positive?y?direction?otherwise?upAux?will?point?downwards
//?effectively?reversing?the?rotation.

	mathsCrossProduct（upAuxlookAtobjToCamProj）;

//?compute?the?angle
	angleCosine?=?mathsInnerProduct（lookAtobjToCamProj）;

//?perform?the?rotation.?The?if?statement?is?used?for?stability?reasons
//?if?the?lookAt?and?v?vectors?are?too?close?together?then?|aux|?could
//?be?bigger?than?1?due?to?lack?of?precision
	if?（（angleCosine??-0.9999））
		glRotatef（acos（angleCosine）*180/3.14upAux[0]?upAux[1]?upAux[2]）;	
}


/*----------------------------------------------------------------
True?billboarding.?With?the?spherical?version?the?object?will?
always?face?the?camera.?It?requires?more?computational?effort?than
the?cylindrical?billboard?though.?The?parameters?camXcamY?and?camZ
are?the?target?i.e.?a?3D?point?to?which?the?object?will?point.
----------------------------------------------------------------*/

void?l3dBillboardSphericalBegin（float?*cam?float?*worldPos）?{

	float?lookAt[3]={001}objToCamProj[3]objToCam[3]upAux[3]angleCosi

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件????????545??2001-10-02?01:15??Smoke_shader\glutsnowman.dsw

?????文件????????489??2001-10-17?23:18??Smoke_shader\fonts.h

?????文件????????419??2001-11-11?04:11??Smoke_shader\l3DBillboard.h

?????文件???????1536??2001-09-27?23:59??Smoke_shader\maths.h

?????文件???????8661??2001-01-02?23:32??Smoke_shader\tga.cpp

?????文件????????827??2000-12-03?00:00??Smoke_shader\tga.h

?????文件?????262683??2000-04-02?00:45??Smoke_shader\tree.tga

?????文件???????1864??2008-11-14?15:40??Smoke_shader\ShaderUtil.h

?????文件?????173056??2008-12-02?16:29??Smoke_shader\glutsnowman.ncb

?????文件???????1784??2008-12-01?16:06??Smoke_shader\glutsnowman.plg

?????文件??????79898??1998-08-18?23:25??Smoke_shader\glut32.lib

?????文件?????169984??1998-08-18?23:25??Smoke_shader\glut32.dll

?????文件???????7105??2008-11-14?15:59??Smoke_shader\billboard.cpp

?????文件???????5176??2002-05-13?15:33??Smoke_shader\spark.bmp

?????文件???????5176??2002-05-15?16:17??Smoke_shader\bubble.bmp

?????文件???????5176??2002-05-15?16:17??Smoke_shader\cloud.bmp

?????文件???????2069??2008-11-14?15:35??Smoke_shader\fonts.cpp

?????文件?????196664??2008-11-14?15:12??Smoke_shader\colorGradient.bmp

?????文件?????192512??2006-03-04?03:19??Smoke_shader\glew32.dll

?????文件?????281360??2006-03-04?03:19??Smoke_shader\glew32.lib

?????文件???????7871??2008-11-14?15:35??Smoke_shader\l3dBillboard.cpp

?????文件??????81920??2008-11-19?16:07??Smoke_shader\glutsnowman.exe

?????文件???????8337??2008-11-14?15:40??Smoke_shader\ShaderUtil.cpp

?????文件????????266??2008-11-14?17:19??Smoke_shader\ParticleUtils.cpp

?????文件????????150??2008-11-14?17:19??Smoke_shader\ParticleUtils.h

?????文件???????2310??2008-11-14?13:45??Smoke_shader\pVector.h

?????文件???????4226??2008-11-18?10:50??Smoke_shader\glutsnowman.dsp

?????文件????????384??2008-11-18?10:45??Smoke_shader\shader\VolumeParticle.vert

?????文件?????169984??1998-08-18?23:25??Smoke_shader\shader\glut32.dll

?????文件?????192512??2006-03-04?03:19??Smoke_shader\shader\glew32.dll

............此處省略49個文件信息