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feat(B.4b): WorldPicker.BuildRay — mouse-to-world ray unprojection

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New AcDream.Core.Selection.WorldPicker static helper. BuildRay
unprojects pixel (mouseX, mouseY) through a view+projection matrix
pair into a world-space (origin, direction) ray. Used by
GameWindow.OnInputAction to drive entity picking on click.

Pure math, no state, no DI. Composes view*projection (System.Numerics
row-vector convention, matching the rest of acdream's camera path —
see GameWindow.cs:6445 FrustumPlanes.FromViewProjection). 2 xUnit
tests cover center-of-viewport (forward ray) and right-of-center
(positive-X deflection).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-05-13 17:41:48 +02:00
parent 179e441d11
commit f0b3bd9aa2
2 changed files with 109 additions and 0 deletions
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54
tests/AcDream.Core.Tests/Selection/WorldPickerTests.cs Normal file
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using System;
using System.Numerics;
using AcDream.Core.Selection;
using Xunit;
namespace AcDream.Core.Tests.Selection;
public class WorldPickerTests
{
private const float Epsilon = 0.01f;
private static (Matrix4x4 View, Matrix4x4 Projection) MakeIdentityCamera()
{
var view = Matrix4x4.Identity;
var proj = Matrix4x4.CreatePerspectiveFieldOfView(
fieldOfView: MathF.PI / 3f,
aspectRatio: 16f / 9f,
nearPlaneDistance: 0.1f,
farPlaneDistance: 100f);
return (view, proj);
}
[Fact]
public void BuildRay_CenterOfViewport_ReturnsForwardRay()
{
var (view, proj) = MakeIdentityCamera();
const float vpW = 1920f, vpH = 1080f;
var (_, direction) = WorldPicker.BuildRay(
mouseX: vpW / 2f, mouseY: vpH / 2f,
viewportW: vpW, viewportH: vpH,
view, proj);
// Right-handed perspective + identity view -> camera looks down -Z.
// Center pixel ray = (0, 0, -1) within float epsilon.
Assert.True(MathF.Abs(direction.X) < Epsilon, $"direction.X = {direction.X}");
Assert.True(MathF.Abs(direction.Y) < Epsilon, $"direction.Y = {direction.Y}");
Assert.True(direction.Z < -0.99f, $"direction.Z = {direction.Z}");
}
[Fact]
public void BuildRay_OffsetMouseRight_DeflectsRayPositiveX()
{
var (view, proj) = MakeIdentityCamera();
const float vpW = 1920f, vpH = 1080f;
var (_, direction) = WorldPicker.BuildRay(
mouseX: vpW * 0.75f, mouseY: vpH / 2f,
viewportW: vpW, viewportH: vpH,
view, proj);
Assert.True(direction.X > 0.1f, $"direction.X = {direction.X} (expected > 0.1)");
}
}