From f2630fd153d573d4f8d450343c697cd64c615fbd Mon Sep 17 00:00:00 2001
From: Brett Laptop <tri11paragon@tpgc.me>
Date: Sat, 7 Jun 2025 22:08:20 -0400
Subject: [PATCH] silly pineapples

---
 CMakeLists.txt                |  2 +-
 include/shaders/particle.frag |  7 +++----
 include/shaders/particle.vert | 14 ++++++++++----
 src/main.cpp                  | 28 ++++++++++++++++++++++++++++
 4 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d4c64aa..62e1407 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.25)
-project(gpu-particles VERSION 0.0.4)
+project(gpu-particles VERSION 0.0.5)
 
 option(ENABLE_ADDRSAN "Enable the address sanitizer" OFF)
 option(ENABLE_UBSAN "Enable the ub sanitizer" OFF)
diff --git a/include/shaders/particle.frag b/include/shaders/particle.frag
index 96d01a4..af9de9c 100644
--- a/include/shaders/particle.frag
+++ b/include/shaders/particle.frag
@@ -4,14 +4,13 @@ const std::string shader_particle_2d_frag = R"("
 #version 300 es
 precision mediump float;
 
-layout (location = 0) in vec4 position_uv;
+uniform sampler2D tex;
 
-out vec2 UVs;
+layout (location = 0) out vec4 FragColor;
 
 void main()
 {
-    gl_Position = vec4(position_uv.x, position_uv.y, 0.0, 1.0);
-    UVs = position_uv.zw;
+    FragColor = texture(tex, gl_PointCoord);
 }
 
 ")";
diff --git a/include/shaders/particle.vert b/include/shaders/particle.vert
index 8de5756..f2e6ddb 100644
--- a/include/shaders/particle.vert
+++ b/include/shaders/particle.vert
@@ -4,14 +4,20 @@ const std::string shader_particle_2d_vert = R"("
 #version 300 es
 precision mediump float;
 
-layout (location = 0) in vec4 position_uv;
+layout (location = 0) in vec2 position;
 
-out vec2 UVs;
+layout (std140) uniform GlobalMatrices
+{
+    mat4 projection;
+    mat4 ortho;
+    mat4 view;
+    mat4 pvm;
+    mat4 ovm;
+};
 
 void main()
 {
-    gl_Position = vec4(position_uv.x, position_uv.y, 0.0, 1.0);
-    UVs = position_uv.zw;
+    gl_Position = ovm * vec4(position.x, position.y, 0.0, 1.0);
 }
 
 ")";
diff --git a/src/main.cpp b/src/main.cpp
index b0f6737..b93fe96 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -18,9 +18,13 @@
 #include "blt/gfx/renderer/resource_manager.h"
 #include "blt/gfx/renderer/batch_2d_renderer.h"
 #include "blt/gfx/renderer/camera.h"
+#include <blt/std/random.h>
 #include <shaders/particle.frag>
 #include <shaders/particle.vert>
 #include <imgui.h>
+#include <blt/std/ranges.h>
+
+constexpr blt::size_t PARTICLE_COUNT = 8192;
 
 blt::gfx::matrix_state_manager global_matrices;
 blt::gfx::resource_manager resources;
@@ -32,6 +36,12 @@ struct particle_t
     blt::vec2 position;
     blt::vec2 velocity;
     blt::vec2 acceleration;
+
+    static particle_t make_particle()
+    {
+        blt::random::random_t random{std::random_device()()};
+        return {blt::vec2{random.get(0.0f, 500.0f), random.get(0.0f, 500.0f)}, blt::vec2{}, blt::vec2{}};
+    }
 };
 
 std::unique_ptr<blt::gfx::vertex_array_t> particle_vao;
@@ -49,6 +59,24 @@ void init(const blt::gfx::window_data&)
 
     particle_shader = std::unique_ptr<shader_t>(shader_t::make(shader_particle_2d_vert, shader_particle_2d_frag));
 
+    for (blt::size_t i = 0; i < PARTICLE_COUNT; i++)
+    {
+        particles.push_back(particle_t::make_particle());
+        alive_particles.push_back(i);
+    }
+
+    particle_vbo = std::make_unique<vertex_buffer_t>();
+    particle_vbo->create(GL_ARRAY_BUFFER);
+    particle_vbo->allocate(sizeof(particle_t) * particles.size(), GL_DYNAMIC_DRAW, particles.data());
+
+    alive_particles_ebo = std::make_unique<element_buffer_t>();
+    alive_particles_ebo->create();
+    alive_particles_ebo->allocate(sizeof(blt::u32) * alive_particles.size(), GL_DYNAMIC_DRAW, alive_particles.data());
+
+    particle_vao = std::make_unique<vertex_array_t>();
+    particle_vao->bindVBO(*particle_vbo, 0, 2, GL_FLOAT, sizeof(particle_t), 0);
+    particle_vao->bindElement(*alive_particles_ebo);
+
     global_matrices.create_internals();
     resources.load_resources();
     renderer_2d.create();