Merge pull request #127 from KhronosGroup/PotOfCoalsAnimationPointer

PotOfCoals animation pointer

Models/PotOfCoalsAnimationPointer/README.body.md

@@ -0,0 +1,25 @@
+## Screenshot
+
+![Screenshot from glTF Sample Viewer](screenshot/screenshot_Large.jpg)
+<br/>_Screenshot from [Babylon.js Sandbox](https://sandbox.babylonjs.com/)._
+
+## Description
+
+This asset uses the extension [KHR_animation_pointer](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_animation_pointer#khr_animation_pointer) to animate a heat refraction effect over the [PotOfCoals asset](../PotOfCoals/README.md).
+
+![Animated GIF of the heat refraction](screenshot/PotOfCoalsAnimationPointer.gif)
+<br/>_The animated heat refraction effect._
+
+## Animation
+
+![Thickness and normal textures](screenshot/thickness_and_normal.jpg)
+<br/>_The refraction effect uses two counter-rotating textures._
+
+A mesh was placed above the coals and assigned a refractive material with [KHR_materials_transmission](https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_materials_transmission/README.md#khr_materials_transmission-) and [KHR_materials_volume](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_volume#khr_materials_volume). The volume thickness texture was animated to rotate counter-clockwise, and the normal texture was animated to rotate in the opposite direction. This causes the refraction animation to be less noticeable as a rotating effect, as the two distortions produce an interference pattern. Each texture uses a radial gradient to gradually flatten the texture towards the outside edges, which helps separate the refraction from the edges of the copper pot.
+
+## Specular
+
+![Disabling the Specular extension](screenshot/specular_disabled.jpg)
+<br/>_The specular extension was used to remove reflections._
+
+The extension [KHR_materials_specular](https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_specular#khr_materials_specular) was added to the refraction mesh to disable all reflections. This prevents the mesh from looking like reflective glass or water, but more like non-reflective air being refracted by heat.