From a199d4189045f96ebdd9b8d5f8cb67b25f960a72 Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Wed, 9 Sep 2026 13:36:53 -0400
Subject: [PATCH] Have 100 cubes flying around in a circle with refraction.

---
 27-instancing/config.json                     |  4 ++++
 .../shaders/27-framebuffers.frag.glsl         | 10 +++++++--
 .../shaders/27-framebuffers.vert.glsl         |  5 -----
 27-instancing/src/config.hpp                  |  2 +-
 27-instancing/src/main.cpp                    |  1 +
 27-instancing/src/scene.cpp                   | 21 ++++++++++++-------
 27-instancing/src/scene.hpp                   |  1 +
 7 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/27-instancing/config.json b/27-instancing/config.json
index 0f7bfeb..367ff25 100644
--- a/27-instancing/config.json
+++ b/27-instancing/config.json
@@ -58,6 +58,10 @@
       "window": {
         "directory": "assets",
         "model_path": "window.glb"
+      },
+      "human": {
+        "directory": "../assets",
+        "model_path": "human.glb"
       }
     },
     "things": [
diff --git a/27-instancing/shaders/27-framebuffers.frag.glsl b/27-instancing/shaders/27-framebuffers.frag.glsl
index 4b161b8..44b8a3d 100644
--- a/27-instancing/shaders/27-framebuffers.frag.glsl
+++ b/27-instancing/shaders/27-framebuffers.frag.glsl
@@ -1,11 +1,17 @@
 #version 330 core
 out vec4 FragColor;
 
+in vec3 Normal;
+in vec3 FragPos;
 in vec2 TexCoords;
 
-uniform sampler2D texture1;
+uniform vec3 cameraPos;
+uniform samplerCube skybox;
 
 void main()
 {
-  FragColor = texture(texture1, TexCoords);
+  float ratio = 1.0/1.52;
+  vec3 I = normalize(FragPos - cameraPos);
+  vec3 R = refract(I, normalize(Normal), ratio);
+  FragColor = vec4(texture(skybox, R).rgb, 1.0);
 }
diff --git a/27-instancing/shaders/27-framebuffers.vert.glsl b/27-instancing/shaders/27-framebuffers.vert.glsl
index c495100..f12b886 100644
--- a/27-instancing/shaders/27-framebuffers.vert.glsl
+++ b/27-instancing/shaders/27-framebuffers.vert.glsl
@@ -16,12 +16,7 @@ uniform vec3 offsets[10];
 
 void main()
 {
-  // THIS WORKS
-  // vec3 in_offset = offsets[gl_InstanceID];
-
-  // THIS DOES NOT, see Scene::setup_instancing and Mesh::draw
   vec3 in_offset = aOffset;
-  // in_offset.x = gl_InstanceID;
 
   vec4 offset = vec4(aPos + in_offset, 1.0);
   gl_Position = projection * view * model * offset;
diff --git a/27-instancing/src/config.hpp b/27-instancing/src/config.hpp
index ee4a201..27c5490 100644
--- a/27-instancing/src/config.hpp
+++ b/27-instancing/src/config.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#define INSTANCE_COUNT 10
+#define INSTANCE_COUNT 100
 
 const unsigned int SCR_WIDTH = 1792;
 const unsigned int SCR_HEIGHT = 1008;
diff --git a/27-instancing/src/main.cpp b/27-instancing/src/main.cpp
index 1ee4fdd..6adcf47 100644
--- a/27-instancing/src/main.cpp
+++ b/27-instancing/src/main.cpp
@@ -144,6 +144,7 @@ int main() {
   glfwSetWindowUserPointer(window, &scene);
 
   while(!glfwWindowShouldClose(window)) {
+    scene.time_warp();
     update(window, scene);
     render(window, scene);
   }
diff --git a/27-instancing/src/scene.cpp b/27-instancing/src/scene.cpp
index 0bb5c70..c2d164d 100644
--- a/27-instancing/src/scene.cpp
+++ b/27-instancing/src/scene.cpp
@@ -84,11 +84,14 @@ void Scene::spawn(const std::string& name, components::Position& position, compo
   }
 }
 
-void Scene::setup_instancing() {
+void Scene::time_warp() {
+  float time = glfwGetTime();
   for(size_t i = 0; i < INSTANCE_COUNT; i++) {
-    translations[i].x = (float)i;
-    translations[i].z = (float)i;
-    translations[i].y = 0.0f;
+    auto& t = translations[i];
+    float factor = (float)i / 3.0f;
+    t.y = cos((time + i)) * factor;
+    t.z = sin((time + i)) * factor;
+    t.x = sin((time + i)) * factor;
   }
 
   glGenBuffers(1, &instanceVBO);
@@ -104,12 +107,16 @@ void Scene::setup_instancing() {
     glBindBuffer(GL_ARRAY_BUFFER, 0);
     glVertexAttribDivisor(3, 1);
   }
+}
 
-  // this works
-  shader.use();
+void Scene::setup_instancing() {
   for(size_t i = 0; i < INSTANCE_COUNT; i++) {
-    shader.setVec3(std::format("offsets[{}]", i), translations[i]);
+    translations[i].x = (float)i;
+    translations[i].z = (float)i;
+    translations[i].y = (float)i;
   }
+
+  time_warp();
 }
 
 void Scene::init_skybox() {
diff --git a/27-instancing/src/scene.hpp b/27-instancing/src/scene.hpp
index 6183569..c6ab8ee 100644
--- a/27-instancing/src/scene.hpp
+++ b/27-instancing/src/scene.hpp
@@ -101,4 +101,5 @@ struct Scene {
   void load_skybox_textures();
   void render_skybox(const glm::mat4& projection);
   void setup_instancing();
+  void time_warp();
 };