From 7502888d0316c3e88cb3bf3fc2e9602f2b44484d Mon Sep 17 00:00:00 2001
From: Evert Prants <imsonotsleepy@gmail.com>
Date: Fri, 1 Mar 2019 12:37:30 +0200
Subject: [PATCH] Camera-based subdivision

---
 src/engine/components/planet/index.js | 48 ++++++++++++++++++++++-----
 src/engine/mesh/aabb.js               | 37 +++++++++++++++++++++
 src/index.js                          |  8 +++--
 3 files changed, 82 insertions(+), 11 deletions(-)
 create mode 100644 src/engine/mesh/aabb.js

diff --git a/src/engine/components/planet/index.js b/src/engine/components/planet/index.js
index f149668..76d4bbf 100644
--- a/src/engine/components/planet/index.js
+++ b/src/engine/components/planet/index.js
@@ -1,5 +1,6 @@
 import { Mesh } from '../../mesh'
-import { mat4 } from 'gl-matrix'
+import { BoundingBox } from '../../mesh/aabb'
+import { mat4, vec3 } from 'gl-matrix'
 import { subv3, mulv3, addv3, normalv3, crossv3 } from '../../utility'
 
 const lodMax = 8
@@ -28,10 +29,6 @@ class CubeFace {
     this.position = subv3(this.position, mulv3(this.left, this.radius / 2))
     this.position = subv3(this.position, mulv3(this.forward, this.radius / 2))
 
-    if (this.parent) {
-      this.transform = this.parent.transform
-    }
-
     this.generate()
   }
 
@@ -88,6 +85,7 @@ class CubeFace {
     }
 
     this.mesh = Mesh.construct(window.gl, vertices, indices, textureCoords)
+    this.bounds = BoundingBox.fromMesh(this.mesh)
     this.generated = true
   }
 
@@ -139,10 +137,6 @@ class CubeFace {
       return
     }
 
-    // Set model transform matrix uniform
-    const transformLocation = shader.getUniformLocation(gl, 'uModelMatrix')
-    gl.uniformMatrix4fv(transformLocation, false, this.transform)
-
     this.mesh.prepare(gl, shader)
     this.mesh.draw(gl, shader)
   }
@@ -174,7 +168,43 @@ class CubePlanet {
     this.faces[0].children[0].subdivide()
   }
 
+  getActiveQuadTreeFaces (face, active) {
+    if (!face.children.length) {
+      active.push(face)
+    } else {
+      for (let f = 0; f < face.children.length; f++) {
+        this.getActiveQuadTreeFaces(face.children[f], active)
+      }
+    }
+  }
+
+  update (f, camera) {
+    let activeTree = []
+    this.getActiveQuadTreeFaces(this.faces[f], activeTree)
+
+    for (let a = 0; a < activeTree.length; a++) {
+      let dist = vec3.distance(camera.pos, activeTree[a].bounds.center)
+
+      if (dist > activeTree[a].radius) {
+        if (dist <= this.radius * 2.0 || activeTree[a].parent === this) {
+          activeTree[a].merge()
+          activeTree[a].generate()
+        } else {
+          activeTree[a].merge()
+          activeTree[a].parent.merge()
+          activeTree[a].parent.generate()
+        }
+      } else if (activeTree[a].radius > this.resolution && activeTree[a].level < lodMax) {
+        activeTree[a].subdivide()
+      }
+    }
+  }
+
   draw (gl, shader) {
+    // Set model transform matrix uniform
+    const transformLocation = shader.getUniformLocation(gl, 'uModelMatrix')
+    gl.uniformMatrix4fv(transformLocation, false, this.transform)
+
     for (let i in this.faces) {
       this.faces[i].draw(gl, shader)
     }
diff --git a/src/engine/mesh/aabb.js b/src/engine/mesh/aabb.js
new file mode 100644
index 0000000..6f1694f
--- /dev/null
+++ b/src/engine/mesh/aabb.js
@@ -0,0 +1,37 @@
+
+class BoundingBox {
+  constructor (min, max) {
+    this.min = min
+    this.max = max
+    this.calculateSphere()
+  }
+
+  static fromMesh (mesh) {
+    let min = [0, 0, 0]
+    let max = [0, 0, 0]
+    for (let v = 0; v < mesh.vertices.length; v += 3) {
+      let vertex = [mesh.vertices[v], mesh.vertices[v + 1], mesh.vertices[v + 2]]
+      // X
+      if (vertex[0] > max[0]) max[0] = vertex[0]
+      if (vertex[0] < min[0]) min[0] = vertex[0]
+      // Y
+      if (vertex[1] > max[1]) max[1] = vertex[1]
+      if (vertex[1] < min[1]) min[1] = vertex[1]
+      // Z
+      if (vertex[2] > max[2]) max[2] = vertex[2]
+      if (vertex[2] < min[2]) min[2] = vertex[2]
+    }
+    return new BoundingBox(min, max)
+  }
+
+  calculateSphere () {
+    this.center = [
+      this.min[0] + (this.max[0] - this.min[0]) / 2,
+      this.min[1] + (this.max[1] - this.min[1]) / 2,
+      this.min[2] + (this.max[2] - this.min[2]) / 2
+    ]
+    this.radius = Math.max((this.max[0] - this.min[0]) / 2, (this.max[1] - this.min[1]) / 2, (this.max[2] - this.min[2]) / 2)
+  }
+}
+
+export { BoundingBox }
diff --git a/src/index.js b/src/index.js
index d5ebd28..f03dbef 100644
--- a/src/index.js
+++ b/src/index.js
@@ -38,9 +38,10 @@ async function pipeline () {
   cam.updateProjection(game.gl)
 
   // Planet test
-  let planet = new CubePlanet([0.0, 0.0, 0.0], 16, 128)
+  let planet = new CubePlanet([0.0, 0.0, 0.0], 16, 512)
 
   // Update function for camera
+  let face = 0
   game.addUpdateFunction(function (dt) {
     if (game.input.isDown('w')) {
       cam.processKeyboard(0, dt)
@@ -61,6 +62,8 @@ async function pipeline () {
     // TESTING: Move model forward
     // t = t + 0.1
     // entity.setPosition([t, 0.0, 0.0])
+    planet.update(face++, cam)
+    if (face > 5) face = 0
   })
 
   // Render function for the triangle
@@ -69,7 +72,7 @@ async function pipeline () {
     cam.draw(gl, shader)
     entity.draw(gl, shader)
     planet.draw(gl, shader)
-
+/*
     // Use terrain shader
     terrainShader.use(gl)
 
@@ -81,6 +84,7 @@ async function pipeline () {
 
     // Draw terrain
     terrain.draw(gl, terrainShader)
+*/
   })
 
   game.startGameLoop()