feat: image based lighting part 2 (specular highlights) (#48)

* add brdf lut to skybox, brdf_lut tests

* added IBL specular highlights

* use mipmaps to soften prefiltering artifacts

Author: schell

DEVLOG.md

@@ -0,0 +1,16 @@
+# devlog
+
+## Wed Aug 2, 2023
+
+When generating mipmaps I ran into a problem where sampling the original texture was always coming up [0.0, 0.0 0.0, 0.0]. It turns out that the sampler was trying to read from the mipmap at level 1, and of course it didn't exist yet as that was the one I was trying to generate. The fix was to sample a different texture - one without slots for the mipmaps, then throw away that texture.
+
+I have to generate mipmaps to smooth out the irradiance and prefiltered cubemaps that we use for pbr shading.
+
+## Thur Aug 3, 2023
+
+I greatly reduced the artifacts in the prefiltered environment cube used for specular highlights.
+I did this by using a simplified `calc_lod` and also by generating enough mipmaps.
+Previously I was only making 5 mip levels but the `calc_lod` was often requiring 21+!
+Of course the environment cubemap's face size is only 512, which leads to 9 mip levels total - so now I'm providing 9 mips.
+
+I also noticed that the IBL diffuse irradiance samples were not aligned! Now the normal's Y is flipped in the irradiance convolution.

NOTES.md

@@ -69,6 +69,7 @@ Just pro-cons on tech choices and little things I don't want to forget whil impl
 * [**Help inspecting buffers in Xcode** ](https://developer.apple.com/documentation/xcode/inspecting-buffers?changes=__9)
 * command that includes some vulkan debugging stuff
   - VK_LOADER_LAYERS_ENABLE='*validation' VK_LAYER_ENABLES=VK_VALIDATION_FEATURE_ENABLE_DEBUG_PRINTF_EXT DEBUG_PRINTF_TO_STDOUT=1
+* When generating mipmaps I ran into a problem where sampling the original texture was always coming up [0.0, 0.0 0.0, 0.0]. It turns out that the sampler was trying to read from the mipmap at level 1, and of course it didn't exist yet as that was the one I was trying to generate. The fix was to sample a different texture - one without slots for the mipmaps, then throw away that texture.
 
 ## PBR reference implementations
 * [khronos sample viewer](https://github.khronos.org/glTF-Sample-Viewer-Release/)

README.md

@@ -40,9 +40,7 @@ Shaders are written in Rust via `rust-gpu` where possible, falling back to `wgsl
 
 Renderling takes a [forward+](https://takahiroharada.files.wordpress.com/2015/04/forward_plus.pdf) approach to rendering.
 
-By default it uses a single uber-shader with a configurable lighting model per material.
-
-This means each model may be shaded separately, with a different lighting style.
+By default it uses a single uber-shader for rendering.
 
 - [ ] frustum culling
 - [ ] occlusion culling
@@ -54,8 +52,8 @@ This means each model may be shaded separately, with a different lighting style.
   - [x] high dynamic range
   - [x] skybox
   - image based lighting
-    - [ ] diffuse
-    - [ ] specular
+    - [x] diffuse
+    - [x] specular
   - [ ] msaa
   - [ ] bloom
   - [ ] ssao

crates/example/src/gltf.rs

@@ -7,8 +7,8 @@ use std::time::Instant;
 use renderling::{
     debug::DebugChannel,
     math::{Mat4, Vec3, Vec4},
-    GltfLoader, GpuEntity, Renderling, Scene, ScreenSize, TweenProperty, UiDrawObjects, UiMode,
-    UiVertex, ViewMut, SceneImage,
+    GltfLoader, GpuEntity, Renderling, Scene, SceneImage, ScreenSize, TweenProperty, UiDrawObjects,
+    UiMode, UiVertex, View, ViewMut,
 };
 use renderling_gpui::{Element, Gpui};
 use winit::event::KeyboardInput;
@@ -97,6 +97,7 @@ impl App {
     }
 
     fn camera_position(radius: f32, phi: f32, theta: f32) -> Vec3 {
+        // convert from spherical to cartesian
         let x = radius * theta.sin() * phi.cos();
         let y = radius * theta.sin() * phi.sin();
         let z = radius * theta.cos();
@@ -150,8 +151,13 @@ impl App {
         self.left_mb_down = false;
         self.last_cursor_position = None;
 
-        let mut builder = r.new_scene().with_debug_channel(DebugChannel::None);
-        //let cross_loader = builder.gltf_load("/Users/schell/code/renderling/gltf/origin_cross.glb").unwrap();
+        let mut builder = r
+            .new_scene()
+            .with_skybox_image_from_path("img/hdr/night.hdr")
+            .with_debug_channel(DebugChannel::None);
+        // let cross_loader =
+        // builder.gltf_load("/Users/schell/code/renderling/gltf/origin_cross.glb").
+        // unwrap();
         let loader = match builder.gltf_load(&file) {
             Ok(loader) => loader,
             Err(msg) => {
@@ -182,24 +188,6 @@ impl App {
         let length = min.distance(max);
         let radius = length * 1.25;
 
-        if loader.lights.len() == 0 {
-            // These values were taken from the Khronos gltf-Sample-Viewer, which is a bit
-            // of a reference implementation as far as GLTF viewers go.
-            // See https://github.com/KhronosGroup/glTF-Sample-Viewer/blob/5b1b7f48a8cb2b7aaef00d08fdba18ccc8dd331b/source/Renderer/renderer.js#L72
-            let _key_light = builder
-                .new_directional_light()
-                .with_color(Vec4::ONE)
-                .with_direction(Vec3::new(0.5, -0.7071, -0.5))
-                .with_intensity(1.0)
-                .build();
-            let _fill_light = builder
-                .new_directional_light()
-                .with_color(Vec4::ONE)
-                .with_direction(Vec3::new(-0.5, 0.7071, 0.5))
-                .with_intensity(0.5)
-                .build();
-        }
-
         let name = get_name(file);
         self.ui.set_text_title(format!("{name}"));
 
@@ -309,7 +297,7 @@ impl App {
                 }
                 let time = animation.stored_timestamp % animation.length_in_seconds();
                 for (id, tween_prop) in animation.get_properties_at_time(time).unwrap() {
-                    let mut ent = self.entities.get_mut(id.index()).unwrap();
+                    let ent = self.entities.get_mut(id.index()).unwrap();
                     match tween_prop {
                         TweenProperty::Translation(t) => {
                             ent.position = t.extend(ent.position.w);
@@ -354,14 +342,12 @@ pub fn demo(
     skybox: Option<std::path::PathBuf>,
 ) -> impl FnMut(&mut Renderling, Option<&winit::event::WindowEvent>) {
     let mut app = App::new(r);
-
     if let Some(file) = model {
         app.load_gltf_model(r, file);
     }
     if let Some(file) = skybox {
         app.load_hdr_skybox(r, file);
     }
-
     let mut event_state = renderling_gpui::EventState::default();
     move |r, ev: Option<&winit::event::WindowEvent>| {
         if let Some(ev) = ev {

crates/renderling-gpui/src/lib.rs

@@ -297,7 +297,6 @@ impl Gpui {
                 })
                 .into(),
         };
-        drop(r);
         let depth_texture = renderling::Texture::create_depth_texture(&device, width, height);
         let mut r = Renderling::new(
             target,

crates/renderling-shader/Cargo.toml

@@ -20,4 +20,8 @@ glam = { version = "0.22", features = ["bytemuck"] }
 glam = { version = "0.22", features = ["debug-glam-assert", "bytemuck"] }
 
 [target.'cfg(target_arch = "spirv")'.dependencies]
-glam = { version = "0.22", default-features = false, features = ["libm", "bytemuck"] }
+glam = { version = "0.22", default-features = false, features = ["libm", "bytemuck"] }
+
+[dev-dependencies]
+image = "^0.24"
+img-diff = { path = "../img-diff" }