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enbugger/RayCasting.cs

Last active August 3, 2025 18:49
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  1. enbugger revised this gist Aug 3, 2025. 1 changed file with 1 addition and 0 deletions.
    1 change: 1 addition & 0 deletions reference.md
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    https://github.com/fenomas/fast-voxel-raycast
  2. enbugger revised this gist Aug 3, 2025. No changes.
  3. enbugger revised this gist Aug 3, 2025. No changes.
  4. enbugger created this gist Aug 3, 2025.
    96 changes: 96 additions & 0 deletions RayCasting.cs
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    using static Unity.Mathematics.math;
    using Unity.Mathematics;

    namespace Game
    {
    public interface IVoxelStore<T> where T : struct
    {
    // Should return null if the guess value is not in boundaries of any voxel
    // Otherwise return arbitrary voxel data
    T? GetVoxel(float3 guess);
    }

    public struct RayCasting
    {
    public static T? Cast<T, TR>(TR store,
    float3 origin, float3 direction, float maxDistance,
    out float3 hitPos, out float3 hitNorm)
    where T : struct
    where TR: struct, IVoxelStore<T>
    {
    if (distance(origin, direction) == 0)
    {
    hitPos = 0;
    hitNorm = 0;
    return null;
    }

    direction = normalize(direction);
    var t = 0f;
    var i = floor(origin);
    var step = sign(direction);
    var tDelta = abs(1 / direction);
    float3 dist;
    dist.x = step.x > 0 ? i.x + 1 - origin.x : origin.x - i.x;
    dist.y = step.y > 0 ? i.y + 1 - origin.y : origin.y - i.y;
    dist.z = step.z > 0 ? i.z + 1 - origin.z : origin.z - i.z;
    float3 tMax;
    tMax.x = tDelta.x < float.PositiveInfinity ? tDelta.x * dist.x : float.PositiveInfinity;
    tMax.y = tDelta.y < float.PositiveInfinity ? tDelta.y * dist.y : float.PositiveInfinity;
    tMax.z = tDelta.z < float.PositiveInfinity ? tDelta.z * dist.z : float.PositiveInfinity;
    var steppedIndex = -1;
    while (t <= maxDistance)
    {
    var b = store.GetVoxel(i);
    if (b != null)
    {
    hitPos = origin + t * direction;
    hitNorm = 0;
    if (steppedIndex >= 0)
    hitNorm[steppedIndex] = -step[steppedIndex];
    return b;
    }

    // Advance t to next nearest voxel boundary
    if (tMax.x < tMax.y)
    {
    if (tMax.x < tMax.z)
    {
    i.x += step.x;
    t = tMax.x;
    tMax.x += tDelta.x;
    steppedIndex = 0;
    }
    else
    {
    i.z += step.z;
    t = tMax.z;
    tMax.z += tDelta.z;
    steppedIndex = 2;
    }
    }
    else
    {
    if (tMax.y < tMax.z)
    {
    i.y += step.y;
    t = tMax.y;
    tMax.y += tDelta.y;
    steppedIndex = 1;
    }
    else
    {
    i.z += step.z;
    t = tMax.z;
    tMax.z += tDelta.z;
    steppedIndex = 2;
    }
    }
    }
    // No voxel hit found
    hitPos = origin + t * direction;
    hitNorm = 0;
    return null;
    }
    }
    }