Cleanup Ray, misc hotfixes (#7)

* Hotfixes

- `Rgb`: Fix originally reversed `/` and `*` logic.
- `Vec`: add missing friend function for `operator-`.

* Add Viewport, cleanup Ray / main

Author: karnkaul

tray/CMakeLists.txt

@@ -9,6 +9,7 @@ target_sources(${PROJECT_NAME} PRIVATE
   src/tray/ray.hpp
   src/tray/rgb.hpp
   src/tray/vec.hpp
+  src/tray/viewport.hpp
 
   src/main.cpp
 )

tray/src/main.cpp

@@ -1,26 +1,32 @@
 #include <tray/image.hpp>
 #include <tray/io.hpp>
 #include <tray/ray.hpp>
-#include <tray/vec.hpp>
+#include <tray/viewport.hpp>
 #include <iostream>
 #include <span>
 
 using namespace tray;
 
 int main() {
 	static constexpr auto extent = uvec2{400U, 300U};
-	static constexpr auto origin = fvec3{0.0f, 0.0f, 0.0f};
-	static constexpr auto horizontal = fvec3(extent.x() / 100.0f, 0.0f, 0.0f);
-	static constexpr auto vertical = fvec3(0.0f, extent.y() / 100.0f, 0.0f);
-	static constexpr auto lower_left = origin - horizontal / 2.0f - vertical / 2.0f - fvec3{0.0f, 0.0f, 1.0f};
+	static constexpr auto viewport = Viewport::make(extent, 2.0f, 2.0f);
+	static constexpr auto origin = fvec3{};
+
+	static constexpr auto horizontal = fvec3{viewport.extent.x(), 0.0f, 0.0f};
+	static constexpr auto vertical = fvec3{0.0f, viewport.extent.y(), 0.0f};
+	static constexpr auto top_left = origin + 0.5f * (-horizontal + vertical) + fvec3{0.0f, 0.0f, -viewport.depth};
+
+	static constexpr fvec3 gradient[] = {Rgb::from_hex(0xffffff).to_f32(), Rgb::from_hex(0x002277).to_f32()};
 	auto image = Image{extent};
+
 	for (std::uint32_t row = 0; row < image.extent().y(); ++row) {
-		auto const yt = static_cast<float>(row) / static_cast<float>(image.extent().y());
+		auto const yt = static_cast<float>(row) / static_cast<float>(image.extent().y() - 1);
 		for (std::uint32_t col = 0; col < image.extent().x(); ++col) {
-			auto const xt = static_cast<float>(col) / static_cast<float>(image.extent().x());
-			auto const ray = Ray{origin, lower_left + xt * horizontal + yt * vertical - origin};
-			auto const t = 0.5f * (normalize(ray.direction.vec()).y() + 1.0f);
-			image[{row, col}] = Rgb::from_f32(Rgb::from_hex(0xff0000).to_f32() * t + (1.0f - t) * Rgb::from_hex(0xffffff).to_f32());
+			auto const xt = static_cast<float>(col) / static_cast<float>(image.extent().x() - 1);
+			auto const dir = top_left + xt * horizontal - yt * vertical - origin;
+			auto const ray = Ray{origin, dir};
+			auto const t = 0.5f * (ray.direction.vec().y() + 1.0f);
+			image[{row, col}] = Rgb::from_f32(lerp(gradient[0], gradient[1], t));
 		}
 	}
 

tray/src/tray/rgb.hpp

@@ -5,8 +5,8 @@ namespace tray {
 struct Rgb : Vec<std::uint8_t, 3> {
 	using Vec::Vec;
 
-	static constexpr float to_f32(std::uint8_t channel) { return static_cast<float>(channel) * 0xff; }
-	static constexpr std::uint8_t to_u8(float channel) { return static_cast<std::uint8_t>(channel / 0xff); }
+	static constexpr float to_f32(std::uint8_t channel) { return static_cast<float>(channel) / 0xff; }
+	static constexpr std::uint8_t to_u8(float channel) { return static_cast<std::uint8_t>(channel * 0xff); }
 
 	static constexpr Rgb from_f32(fvec3 const& normalized) { return {to_u8(normalized.x()), to_u8(normalized.y()), to_u8(normalized.z())}; }
 

tray/src/tray/vec.hpp

@@ -98,6 +98,12 @@ class Vec {
 		return *this;
 	}
 
+	friend constexpr Vec operator-(Vec const& v) {
+		auto ret = v;
+		ret = -ret;
+		return ret;
+	}
+
 	template <VecOrType<Type, Dim> T>
 	friend constexpr Vec operator+(Vec const& a, T const& b) {
 		auto ret = a;

tray/src/tray/viewport.hpp

@@ -0,0 +1,14 @@
+#pragma once
+#include <tray/vec.hpp>
+
+namespace tray {
+struct Viewport {
+	fvec2 extent{1.0f};
+	float depth{1.0f};
+
+	static constexpr Viewport make(uvec2 extent, float depth, float scale = 1.0f) {
+		auto const ar = static_cast<float>(extent.x()) / static_cast<float>(extent.y());
+		return ar > 1.0f ? Viewport{fvec2{scale, scale / ar}, depth} : Viewport{fvec2{scale * ar, scale}, depth};
+	}
+};
+} // namespace tray