From 57e6e562175f1e778bf65245e9902325ba75daae Mon Sep 17 00:00:00 2001
From: Andreas Ortmann <ortmann@finf.uni-hannover.de>
Date: Sun, 2 Oct 2016 17:22:47 +0200
Subject: [PATCH] making code for particle batch modular.

---
 data/shader/particle.vert                     | 17 +++--
 game/renderer_polygon_3d/particle_batch.cpp   | 69 ++++++++++---------
 game/renderer_polygon_3d/particle_batch.hpp   | 30 +++++---
 .../renderer_polygon_3d.cpp                   |  3 +-
 4 files changed, 73 insertions(+), 46 deletions(-)

diff --git a/data/shader/particle.vert b/data/shader/particle.vert
index 68f698d..b445d97 100644
--- a/data/shader/particle.vert
+++ b/data/shader/particle.vert
@@ -1,7 +1,8 @@
 #version 120
-attribute vec2 in_vertex;
-attribute vec3 in_position;
-attribute vec3 in_velocity;
+attribute vec2  in_geometry;
+attribute vec3  in_position;
+attribute vec3  in_velocity;
+attribute float in_maxDist;
 
 uniform float age;
 uniform float size;
@@ -28,11 +29,17 @@ void main()
   decay = ageMod / halfAge;
 
   // faster particles are smaller
+  // TODO: scale by time too! scale down fast after 3 halfAges
   float scaleBySpeed = (1.0 - 0.95*length(in_velocity)/maxVelocity);
   float finalSize = size * scaleBySpeed;
-  vec2 base = in_vertex;
+  vec2 base = in_geometry;
   vec3 p = finalSize*vec3(base, 0.0);
-  vec3 offset = (0.2*age + log(1.0+age*5.0)) * in_velocity + in_position;
+  vec3 move = (0.2*age + log(1.0+age*5.0)) * in_velocity;
+  float md = length(move);
+  if (md > in_maxDist) {
+    move *= in_maxDist / md;
+  }
+  vec3 offset = move + in_position;
   p += offset;
 
   gl_Position = vec4(p, 1.0);
diff --git a/game/renderer_polygon_3d/particle_batch.cpp b/game/renderer_polygon_3d/particle_batch.cpp
index 8fa8fec..755c6af 100644
--- a/game/renderer_polygon_3d/particle_batch.cpp
+++ b/game/renderer_polygon_3d/particle_batch.cpp
@@ -4,7 +4,7 @@
 
 // TODO: use VAO's as soon as this is working
 
-int getDivisorForIndex(int index)
+int getDivisorForIndex(size_t index)
 {
     // 0 or 1?
     return (index == 0) ? 0 : 3;
@@ -20,42 +20,52 @@ namespace endofthejedi {
         , m_maxVelocity(1.0)
         , m_center(glm::vec3(0.0f, 0.0f, 0.0f))
 
-        // 2d quad drawn as a triangle fan
-        , m_data_quad({
+        // 2d quad drawn as a triangle fan.
+        //
+        // TODO
+        // it is transformed before uploading so it looks at the camera
+        , m_data_geometry({
                 1.0f, -1.0f,
                 1.0f,  1.0f,
                -1.0f,  1.0f,
                -1.0f, -1.0f})
     {
+        m_num_vertex_buffers = 4;
+
         //std::cout<<"[ParticleBatch] create for " << numParticles << " num particles" << std::endl;
+        m_attr_locations.resize(m_num_vertex_buffers);
+        m_data_vbos.resize(m_num_vertex_buffers);
 
         m_data_position.resize(m_numParticles);
         m_data_velocity.resize(m_numParticles);
-        m_data_kind.resize(m_numParticles);
-        m_data_max_age.resize(m_numParticles);
+        m_data_max_distance.resize(m_numParticles);
+
+        for (size_t i=0; i<m_num_vertex_buffers; i++) {
+            m_attr_locations[i] = -1;
+            m_data_vbos[i]      =  0;
+        }
     }
 
     ParticleBatch::~ParticleBatch()
     {
         // TODO: find out if stuff must be deallocated
-        glDeleteBuffers(5, m_data_vbos);
+        glDeleteBuffers(m_num_vertex_buffers, m_data_vbos.data());
     }
 
     void ParticleBatch::setup(Shader *shader)
     {
-        const char *names[] = {
-            "in_vertex",
+        static const char *names[] = {
+            "in_geometry",
             "in_position",
             "in_velocity",
-            "XXXunusedXXX",
-            "XXXunusedXXX"
+            "in_maxDist"
         };
 
-        for (int i=0; i<5; i++) {
+        for (size_t i=0; i<m_num_vertex_buffers; i++) {
             const char *name = names[i];
             GLint loc = glGetAttribLocation(shader->program(), name);
             m_attr_locations[i] = loc;
-            //std::cout<<"attr location " << i << " " << loc << " " << name << std::endl;
+            //std::cout<<"attr location for " << name << " (#"  << i << ") is " << loc << std::endl;
         }
     }
 
@@ -69,7 +79,7 @@ namespace endofthejedi {
         m_maxVelocity = maxVelocity;
     }
 
-    void ParticleBatch::setParticle(size_t index, const glm::vec3 &p, const glm::vec3 &v)
+    void ParticleBatch::setParticle(size_t index, const glm::vec3 &p, const glm::vec3 &v, float maxDist)
     {
         if (index >= m_numParticles) {
             return;
@@ -77,17 +87,16 @@ namespace endofthejedi {
 
         //std::cout<<"[ParticleBatch] setParticle " << index << std::endl;
 
-        m_data_position[index] = p;
-        m_data_velocity[index] = v;
-        m_data_kind[index]     = 0.0;
-        m_data_max_age[index]  = 0.0;
+        m_data_position[index]      = p;
+        m_data_velocity[index]      = v;
+        m_data_max_distance[index]  = maxDist;
     }
 
     void ParticleBatch::bind()
     {
         //std::cout<<"[ParticleBatch] bind" << std::endl;
 
-        for (size_t i=0; i<5; i++) {
+        for (size_t i=0; i<m_num_vertex_buffers; i++) {
             //std::cout<<"vbo #" << i << ": " << m_data_vbos[i] << std::endl;
             glEnableVertexAttribArray(m_attr_locations[i]);
             glBindBuffer(GL_ARRAY_BUFFER, m_data_vbos[i]);
@@ -109,9 +118,9 @@ namespace endofthejedi {
     {
         //std::cout<<"[ParticleBatch] upload to vbo's " << std::endl;
 
-        glGenBuffers(5, m_data_vbos);            // Generate buffer
+        glGenBuffers(m_num_vertex_buffers, m_data_vbos.data());            // Generate buffer
 
-        for (size_t i=0; i<5; i++) {
+        for (size_t i=0; i<m_num_vertex_buffers; i++) {
             size_t bufferDataSize = dataSizeForIndex(i) * m_numParticles * sizeof(float);
 
             glEnableVertexAttribArray(i);
@@ -148,7 +157,7 @@ namespace endofthejedi {
 #if 0
         glBegin(GL_QUADS);
         for (size_t index=0; index<m_numParticles; index++) {
-            for (int i=0; i<4; i++) {
+            for (size_t i=0; i<4; i++) {
                 glm::vec2 p = m_data_position[index] + triangles[i];
                 //glColor3f(1.0, 0.0, 0.0);
                 glVertex2f(p.x, p.y);
@@ -159,9 +168,9 @@ namespace endofthejedi {
 
     }
 
-    size_t ParticleBatch::dataSizeForIndex(int i)
+    size_t ParticleBatch::dataSizeForIndex(size_t index)
     {
-        switch(i) {
+        switch(index) {
             case 0:
                 return 2;
 
@@ -170,25 +179,23 @@ namespace endofthejedi {
                 return 3;
 
             case 3:
-            case 4:
                 return 1;
 
             default:
-                std::cerr << "bad" << std::endl;
+                std::cerr << "dataSizeForIndex() bad" << std::endl;
                 exit(-1);
         }
     }
 
-    void *ParticleBatch::dataSourceForIndex(int i)
+    void *ParticleBatch::dataSourceForIndex(size_t index)
     {
-        switch(i) {
-            case 0: return (void *) m_data_quad.data();
+        switch(index) {
+            case 0: return (void *) m_data_geometry.data();
             case 1: return (void *) m_data_position.data();
             case 2: return (void *) m_data_velocity.data();
-            case 3: return (void *) m_data_kind.data();
-            case 4: return (void *) m_data_max_age.data();
+            case 3: return (void *) m_data_max_distance.data();
             default:
-                std::cerr << "bad" << std::endl;
+                std::cerr << "dataSourceForIndex() bad" << std::endl;
                 exit(-1);
         }
     }
diff --git a/game/renderer_polygon_3d/particle_batch.hpp b/game/renderer_polygon_3d/particle_batch.hpp
index 72ddf28..5b7bc69 100644
--- a/game/renderer_polygon_3d/particle_batch.hpp
+++ b/game/renderer_polygon_3d/particle_batch.hpp
@@ -7,6 +7,14 @@
 
 #include "glclasses.hpp"
 
+//class VertexAttribute {
+//    std::string nameInShader;
+//    Guint attributeIndex;
+//    Type type;
+//    modifictaion
+//    void *dataSource;
+//};
+
 namespace endofthejedi {
     class ParticleBatch {
         public:
@@ -17,7 +25,7 @@ namespace endofthejedi {
 
             size_t numParticles() const { return m_numParticles; }
 
-            void setParticle(size_t index, const glm::vec3 &p, const glm::vec3 &v);
+            void setParticle(size_t index, const glm::vec3 &p, const glm::vec3 &v, float maxDistance);
 
             void setCenter(const glm::vec3 &center);
             void setMaxVelocity(float maxVelocity);
@@ -33,11 +41,14 @@ namespace endofthejedi {
             size_t id() const { return m_id; }
 
         private:
-            size_t dataSizeForIndex(int i);
-            void  *dataSourceForIndex(int i);
+            size_t dataSizeForIndex(size_t index);
+            void  *dataSourceForIndex(size_t index);
 
         private:
+            // id of explosion
             size_t                 m_id;
+
+            // uniforms for the shader
             size_t                 m_numParticles;
             float                  m_particleRadius;
             const float            m_halfAge;
@@ -45,14 +56,15 @@ namespace endofthejedi {
             float                  m_maxVelocity;
             glm::vec3              m_center;
 
-            GLuint                 m_data_vbos[5];
+            // meta data
+            size_t                 m_num_vertex_buffers;
+            std::vector<GLuint>    m_data_vbos;
+            std::vector<GLuint>    m_attr_locations;
 
-            std::vector<float>     m_data_quad;
+            // vertex attributes
+            std::vector<float>     m_data_geometry;
             std::vector<glm::vec3> m_data_position;
             std::vector<glm::vec3> m_data_velocity;
-            std::vector<float>     m_data_kind;
-            std::vector<float>     m_data_max_age;
-
-            GLuint                 m_attr_locations[5];
+            std::vector<float>     m_data_max_distance;
     };
 }
diff --git a/game/renderer_polygon_3d/renderer_polygon_3d.cpp b/game/renderer_polygon_3d/renderer_polygon_3d.cpp
index 1c2ad02..47295ac 100644
--- a/game/renderer_polygon_3d/renderer_polygon_3d.cpp
+++ b/game/renderer_polygon_3d/renderer_polygon_3d.cpp
@@ -124,7 +124,8 @@ namespace endofthejedi {
             glm::vec3 v = glm::ballRand(maxVelocity);
             v *= util::randf_0_1() * util::randf_0_1() * util::randf_0_1();
 
-            batch->setParticle(i, glm::vec3(pos, 0.0) + glm::ballRand(explCoreSize), v);
+            float maxDist = 0.2;
+            batch->setParticle(i, glm::vec3(pos, 0.0) + glm::ballRand(explCoreSize), v, maxDist);
         }
 
         batch->upload();