From 9faf5f9496e53871489bd22c8fe752136a07a812 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 11 Apr 2006 13:22:59 +0000
Subject: [PATCH] Added support for point sprite particle effects.

---
 examples/osgprecipitation/osgprecipitation.cpp | 17 +++++++++++++----
 examples/osgprecipitation/point_rain.frag      |  4 ++--
 examples/osgprecipitation/point_rain.vert      | 11 +++++++++++
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/examples/osgprecipitation/osgprecipitation.cpp b/examples/osgprecipitation/osgprecipitation.cpp
index d800641cb..a27250938 100644
--- a/examples/osgprecipitation/osgprecipitation.cpp
+++ b/examples/osgprecipitation/osgprecipitation.cpp
@@ -21,6 +21,8 @@
 #include <osg/PointSprite>
 #include <osg/Program>
 #include <osg/Fog>
+#include <osg/Point>
+#include <osg/PointSprite>
 #include <osg/io_utils>
 
 float random(float min,float max) { return min + (max-min)*(float)rand()/(float)RAND_MAX; }
@@ -252,7 +254,7 @@ osg::Node* createRainEffect(const osg::BoundingBox& bb, const osg::Vec3& velocit
     osg::Geometry* line_geometry = 0;
     osg::Geometry* point_geometry = 0;
     
-#if 1
+#if 0
     quad_geometry = new PrecipitationGeometry;
     quad_geometry->setUseVertexBufferObjects(true);
     quad_geometry->setInitialBound(bb);
@@ -269,7 +271,7 @@ osg::Node* createRainEffect(const osg::BoundingBox& bb, const osg::Vec3& velocit
     }
 #endif
 
-#if 0    
+#if 0   
     line_geometry = new PrecipitationGeometry;
     line_geometry->setUseVertexBufferObjects(true);
     line_geometry->setInitialBound(bb);
@@ -287,7 +289,7 @@ osg::Node* createRainEffect(const osg::BoundingBox& bb, const osg::Vec3& velocit
 #endif
 
 
-#if 0    
+#if 1    
     point_geometry = new PrecipitationGeometry;
     point_geometry->setUseVertexBufferObjects(true);
     point_geometry->setInitialBound(bb);
@@ -300,7 +302,14 @@ osg::Node* createRainEffect(const osg::BoundingBox& bb, const osg::Vec3& velocit
 
         // get shaders from source
         program->addShader(osg::Shader::readShaderFile(osg::Shader::VERTEX, osgDB::findDataFile("point_rain.vert")));
-        program->addShader(osg::Shader::readShaderFile(osg::Shader::FRAGMENT, osgDB::findDataFile("point_rain.frag")));
+        program->addShader(osg::Shader::readShaderFile(osg::Shader::FRAGMENT, osgDB::findDataFile("rain.frag")));
+
+        /// Setup the point sprites
+        osg::PointSprite *sprite = new osg::PointSprite();
+        point_stateset->setTextureAttributeAndModes(0, sprite, osg::StateAttribute::ON);
+
+        point_stateset->setMode(GL_VERTEX_PROGRAM_POINT_SIZE, osg::StateAttribute::ON);
+
     }
 #endif
 
diff --git a/examples/osgprecipitation/point_rain.frag b/examples/osgprecipitation/point_rain.frag
index 506331f4c..7f7be861b 100644
--- a/examples/osgprecipitation/point_rain.frag
+++ b/examples/osgprecipitation/point_rain.frag
@@ -1,8 +1,8 @@
 uniform sampler2D baseTexture;
-uniform vec4 particleColour;
 varying vec2 texCoord;
+varying vec4 colour;
 
 void main (void)
 {
-    gl_FragColor = particleColour * texture2D( baseTexture, texCoord);
+    gl_FragColor = colour * texture2D( baseTexture, texCoord);
 }
diff --git a/examples/osgprecipitation/point_rain.vert b/examples/osgprecipitation/point_rain.vert
index 6a1ac1c1f..d2a6208a8 100644
--- a/examples/osgprecipitation/point_rain.vert
+++ b/examples/osgprecipitation/point_rain.vert
@@ -5,18 +5,29 @@ uniform vec3 dv_k;
 
 uniform float inversePeriod;
 uniform float startTime;
+uniform vec4 particleColour;
 
 uniform float osg_FrameTime;
 
+varying vec4 colour;
 varying vec2 texCoord;
 
 void main(void)
 {
+    const float particleSize = 0.01;
+
     vec3 pos = position + (gl_Vertex.x*dv_i) + (dv_j * gl_Vertex.y);
     
     texCoord = gl_MultiTexCoord0.xy;
 
     vec3 v_current = pos + dv_k * fract( (osg_FrameTime - startTime)*inversePeriod - gl_Vertex.z);
    
+    colour = particleColour;
+
     gl_Position = gl_ModelViewProjectionMatrix * vec4(v_current,1.0);
+
+    float pointSize = min(abs(1280*particleSize / gl_Position.w), 20.0);
+    gl_PointSize = max(ceil(pointSize),2);
+    
+    colour.a = 0.2+(pointSize)/(gl_PointSize);
 }