feat: 1995

engine/scene/Camera.ts

@@ -0,0 +1,35 @@
+import { Mat4 } from "../math/Mat4"
+import { Vec3 } from "../math/Vec3"
+
+/** First-person camera. Orientation is Euler yaw/pitch (no roll), which is all
+ *  an FPS needs and avoids gimbal bookkeeping. */
+export type Camera = {
+  position: Vec3
+  /** Rotation around +Y, radians. 0 looks toward -Z; increasing turns right. */
+  yaw: number
+  /** Look up/down, radians. Positive looks up. Clamp near +-pi/2 to avoid flip. */
+  pitch: number
+  /** Vertical field of view, radians. */
+  fov: number
+}
+
+export namespace Camera {
+  /** Unit forward direction implied by yaw/pitch. */
+  export function forward(cam: Camera): Vec3 {
+    const cp = Math.cos(cam.pitch)
+    return {
+      x: cp * Math.sin(cam.yaw),
+      y: Math.sin(cam.pitch),
+      z: -cp * Math.cos(cam.yaw),
+    }
+  }
+
+  /** Combined projection * view matrix for the given viewport aspect ratio.
+   *  Near/far are fixed for now; far only needs to exceed the fog distance. */
+  export function viewProjection(cam: Camera, aspect: number): Mat4 {
+    const eye = cam.position
+    const view = Mat4.lookAt(eye, Vec3.add(eye, forward(cam)), { x: 0, y: 1, z: 0 })
+    const proj = Mat4.perspective(cam.fov, aspect, 0.05, 100)
+    return Mat4.multiply(proj, view)
+  }
+}