From 1a0831c5ed0e4d172dcf4c912e435c195da3da50 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Thu, 11 Jun 2009 21:43:06 +0100
Subject: [PATCH] Use glDepthMask to avoid sorting billboards

---
 src/Billboard.cpp  |  8 ++++++++
 src/SmokeTrail.cpp | 15 ++-------------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/src/Billboard.cpp b/src/Billboard.cpp
index 396175f..1024ddd 100644
--- a/src/Billboard.cpp
+++ b/src/Billboard.cpp
@@ -122,6 +122,9 @@ void CylindricalBillboard::render() const
    // http://www.lighthouse3d.com/opengl/billboarding/index.php?billCheat1
    
    float modelview[16];
+
+   glPushAttrib(GL_DEPTH_BUFFER_BIT);
+   glDepthMask(GL_FALSE);
    
    glPushMatrix();
 
@@ -142,6 +145,7 @@ void CylindricalBillboard::render() const
    drawTextureQuad();
 
    glPopMatrix();
+   glPopAttrib();
 }
 
 // A billboard which always faces the viewer
@@ -161,6 +165,9 @@ void SphericalBillboard::render() const
    Vector<float> lookAt, objToCamProj, upAux, objToCam;
    float angleCosine;
    
+   glPushAttrib(GL_DEPTH_BUFFER_BIT);
+   glDepthMask(GL_FALSE);
+   
    glPushMatrix();
 
    translate();
@@ -227,6 +234,7 @@ void SphericalBillboard::render() const
    drawTextureQuad();
 
    glPopMatrix();
+   glPopAttrib();
 }
 
 IBillboardPtr makeCylindricalBillboard(ITexturePtr aTexture)
diff --git a/src/SmokeTrail.cpp b/src/SmokeTrail.cpp
index bf1d83e..67d8ee3 100644
--- a/src/SmokeTrail.cpp
+++ b/src/SmokeTrail.cpp
@@ -50,7 +50,7 @@ private:
    void newParticle();
    bool moveParticle(Particle& aParticle, int aDelta);
    
-   mutable list<Particle> myParticles;  // Need to sort particles in render()
+   list<Particle> myParticles; 
    float myX, myY, myZ;
    IBillboardPtr myBillboard;
 
@@ -159,19 +159,8 @@ void SmokeTrail::newParticle()
    myParticles.push_back(p);
 }
 
-struct CmpDistanceToCam {
-   bool operator()(const SmokeTrail::Particle& lhs,
-                   const SmokeTrail::Particle& rhs)
-   {
-      return distanceToCamera(makeVector(lhs.x, lhs.y, lhs.z))
-         > distanceToCamera(makeVector(rhs.x, rhs.y, rhs.z));
-   }
-};
-
 void SmokeTrail::render() const
-{
-   myParticles.sort(CmpDistanceToCam());
-   
+{   
    for (list<Particle>::const_iterator it = myParticles.begin();
         it != myParticles.end(); ++it) {
       myBillboard->setPosition((*it).x, (*it).y, (*it).z);
-- 
2.39.2