From 51023ceb81b78ab7f2bd396742a287556589f6bb Mon Sep 17 00:00:00 2001
From: vincentlj <vincentlj@178a84e3-b1eb-0310-8ba1-8eac791a3b58>
Date: Tue, 7 Jan 2014 00:04:43 +0000
Subject: [PATCH] GPUParticles: Fix adjusted_initial_velocity computation.

Thank to Auria and hiker for their help.

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@14947 178a84e3-b1eb-0310-8ba1-8eac791a3b58
---
 data/shaders/pointemitter.vert | 4 +---
 src/graphics/gpuparticles.cpp  | 6 ------
 src/graphics/gpuparticles.h    | 2 +-
 3 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/data/shaders/pointemitter.vert b/data/shaders/pointemitter.vert
index 48a192906..9a448228e 100644
--- a/data/shaders/pointemitter.vert
+++ b/data/shaders/pointemitter.vert
@@ -1,7 +1,6 @@
 #version 130
 uniform int dt;
 uniform mat4 sourcematrix;
-uniform mat4 tinvsourcematrix;
 uniform int level;
 uniform float size_increase_factor;
 
@@ -23,8 +22,7 @@ out float new_size;
 void main(void)
 {
   vec4 initialposition = sourcematrix * vec4(particle_position_initial, 1.0);
-  vec4 adjusted_initial_velocity = tinvsourcematrix * vec4(particle_velocity_initial, 1.0);
-  adjusted_initial_velocity /= adjusted_initial_velocity.w;
+  vec4 adjusted_initial_velocity = sourcematrix * vec4(particle_position_initial + particle_velocity_initial, 1.0) - initialposition;
   float adjusted_lifetime = lifetime  + (float(dt)/lifetime_initial);
   bool reset = (adjusted_lifetime > 1.) && (gl_VertexID <= level);
   reset = reset || (lifetime < 0.);
diff --git a/src/graphics/gpuparticles.cpp b/src/graphics/gpuparticles.cpp
index 2cbafa660..1625d7cbb 100644
--- a/src/graphics/gpuparticles.cpp
+++ b/src/graphics/gpuparticles.cpp
@@ -240,7 +240,6 @@ GLuint ParticleSystemProxy::attrib_initial_lifetime;
 GLuint ParticleSystemProxy::attrib_size;
 GLuint ParticleSystemProxy::attrib_initial_size;
 GLuint ParticleSystemProxy::uniform_sourcematrix;
-GLuint ParticleSystemProxy::uniform_tinvsourcematrix;
 GLuint ParticleSystemProxy::uniform_dt;
 GLuint ParticleSystemProxy::uniform_level;
 GLuint ParticleSystemProxy::uniform_size_increase_factor;
@@ -315,7 +314,6 @@ void ParticleSystemProxy::setEmitter(scene::IParticleEmitter* emitter)
 
 	uniform_dt = glGetUniformLocation(SimulationProgram, "dt");
 	uniform_sourcematrix = glGetUniformLocation(SimulationProgram, "sourcematrix");
-	uniform_tinvsourcematrix = glGetUniformLocation(SimulationProgram, "tinvsourcematrix");
 	uniform_level = glGetUniformLocation(SimulationProgram, "level");
 	uniform_size_increase_factor = glGetUniformLocation(SimulationProgram, "size_increase_factor");
 
@@ -356,9 +354,6 @@ void ParticleSystemProxy::simulate()
 	LastEmitTime = time;
 	int active_count = getEmitter()->getMaxLifeTime() * getEmitter()->getMaxParticlesPerSecond() / 1000;
 	core::matrix4 matrix = getAbsoluteTransformation();
-	core::matrix4 tinvmatrix;
-	matrix.getInverse(tinvmatrix);
-	tinvmatrix = tinvmatrix.getTransposed();
 	glUseProgram(SimulationProgram);
 	glEnable(GL_RASTERIZER_DISCARD);
 	glEnableVertexAttribArray(attrib_position);
@@ -384,7 +379,6 @@ void ParticleSystemProxy::simulate()
 	glUniform1i(uniform_dt, timediff);
 	glUniform1i(uniform_level, active_count);
 	glUniformMatrix4fv(uniform_sourcematrix, 1, GL_FALSE, matrix.pointer());
-	glUniformMatrix4fv(uniform_tinvsourcematrix, 1, GL_FALSE, tinvmatrix.pointer());
 	glUniform1f(uniform_size_increase_factor, size_increase_factor);
 	glBeginTransformFeedback(GL_POINTS);
 	glDrawArrays(GL_POINTS, 0, count);
diff --git a/src/graphics/gpuparticles.h b/src/graphics/gpuparticles.h
index a6579919f..4f0dac86d 100644
--- a/src/graphics/gpuparticles.h
+++ b/src/graphics/gpuparticles.h
@@ -33,7 +33,7 @@ protected:
 
 	static GLuint SimulationProgram;
 	static GLuint attrib_position, attrib_velocity, attrib_lifetime, attrib_initial_position, attrib_initial_velocity, attrib_initial_lifetime, attrib_size, attrib_initial_size;
-	static GLuint uniform_sourcematrix, uniform_tinvsourcematrix, uniform_dt, uniform_level, uniform_size_increase_factor;
+	static GLuint uniform_sourcematrix, uniform_dt, uniform_level, uniform_size_increase_factor;
 
 	static GLuint RenderProgram;
 	static GLuint attrib_pos, attrib_lf, attrib_quadcorner, attrib_texcoord, attrib_sz;