From 5d643ddb4efa2b5eb1cd8e123ef0dd59b85eed42 Mon Sep 17 00:00:00 2001
From: Adrian G L <adrian@lauterer.it>
Date: Thu, 18 Sep 2025 10:53:44 +0200
Subject: [PATCH] feat: render a large grid of point-particles as billboards
 with program point size enabled

---
 src/main.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index d2a8c69..d739398 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -163,6 +163,7 @@ fn main() {
             gl::Disable(gl::MULTISAMPLE);
             gl::Enable(gl::BLEND);
             gl::BlendFunc(gl::SRC_ALPHA, gl::ONE_MINUS_SRC_ALPHA);
+            gl::Enable(gl::PROGRAM_POINT_SIZE);
             gl::Enable(gl::DEBUG_OUTPUT_SYNCHRONOUS);
             gl::DebugMessageCallback(Some(util::debug_callback), ptr::null());
 
@@ -238,6 +239,22 @@ fn main() {
         ];
         let billboard_vao = unsafe { create_vao(&billboard_vertices, &billboard_colors, &billboard_indices) };
 
+        // Generate a grid of point‐particles
+        let grid_size = 200;
+        let mut particle_vertices = Vec::with_capacity(grid_size * grid_size * 3);
+        let mut particle_colors   = Vec::with_capacity(grid_size * grid_size * 4);
+        for i in 0..grid_size {
+            for j in 0..grid_size {
+                let x = (i as f32 / grid_size as f32 - 0.5) * 20.0;
+                let y = (j as f32 / grid_size as f32 - 0.5) * 20.0;
+                let z = -5.0;
+                particle_vertices.extend_from_slice(&[x, y, z]);
+                particle_colors.extend_from_slice(&[1.0, 1.0, 1.0, 1.0]);
+            }
+        }
+        let particle_vao   = unsafe { create_vao(&particle_vertices, &particle_colors, &Vec::new()) };
+        let particle_count = (grid_size * grid_size) as i32;
+
         // == // Set up your shaders here
 
         // Basic usage of shader helper:
@@ -375,6 +392,12 @@ fn main() {
                     std::ptr::null(),
                 );
 
+                // Draw point‐particles
+                let transform_particles = projection * view * glm::identity();
+                gl::UniformMatrix4fv(transform_loc, 1, gl::FALSE, transform_particles.as_ptr());
+                gl::BindVertexArray(particle_vao);
+                gl::DrawArrays(gl::POINTS, 0, particle_count);
+
                 // Draw billboard (camera-facing quad)
                 let translation_bill = glm::translation(&glm::vec3(0.0, 0.0, -2.0));
                 let inv_rot_y = glm::rotation(cam_yaw, &glm::vec3(0.0, 1.0, 0.0));