From 9a4b92160585657347a8f9a7fe96fff443714d58 Mon Sep 17 00:00:00 2001
From: rude <none@none>
Date: Sun, 24 Jul 2011 18:47:13 +0200
Subject: [PATCH] Particles now have fixed origin. (ParticleSystem::SetPosition
 will only affect new particles, and existing particles will not gravitate
 against the new point).

This is another requirement to implement ParticleSystem in GLSL.
---
 src/modules/graphics/opengl/ParticleSystem.cpp | 4 +++-
 src/modules/graphics/opengl/ParticleSystem.h   | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/modules/graphics/opengl/ParticleSystem.cpp b/src/modules/graphics/opengl/ParticleSystem.cpp
index 2d8a5fe6a..a5044d6c5 100644
--- a/src/modules/graphics/opengl/ParticleSystem.cpp
+++ b/src/modules/graphics/opengl/ParticleSystem.cpp
@@ -95,6 +95,8 @@ namespace opengl
 		max = direction + spread/2.0f;
 		pLast->direction = (rand() / (float(RAND_MAX)+1)) * (max - min) + min;
 
+		pLast->origin = position;
+
 		min = speedMin;
 		max = speedMax;
 		float speed = (rand() / (float(RAND_MAX)+1)) * (max - min) + min;
@@ -447,7 +449,7 @@ namespace opengl
 				love::Vector ppos(p->position[0], p->position[1]);
 
 				// Get vector from particle center to particle.
-				radial = ppos - position;
+				radial = ppos - p->origin;
 				radial.normalize();
 				tangential = radial;
 
diff --git a/src/modules/graphics/opengl/ParticleSystem.h b/src/modules/graphics/opengl/ParticleSystem.h
index 0af4f0bd6..6514d1568 100644
--- a/src/modules/graphics/opengl/ParticleSystem.h
+++ b/src/modules/graphics/opengl/ParticleSystem.h
@@ -46,6 +46,9 @@ namespace opengl
 		float position[2];
 		float direction;
 
+		// Particles gravitate towards this point.
+		love::Vector origin;
+
 		love::Vector speed;
 		float gravity;
 		float radialAcceleration;