/// <summary>
/// Intersect a ray against this object.
/// </summary>
/// <param name="start">The start position of the ray, in object space.</param>
/// <param name="dir">The direction of the ray, in object space (not a unit vector).</param>
/// <returns>Information about the nearest intersection, or null if no intersection.</returns>
public IntersectionInfo IntersectRay(Vector start, Vector dir, RenderContext context)
{
// TODO: some rays should be short (e.g. ambient occlusion rays). Make the max ray distance an optional parameter?
Vector end = start + dir * 10;
//if (!boundingBox.OverlapsLineSegment(start, end))
// TODO: clipping line segment breaks IntersectionInfo.rayFrac, because ray is truncated, but rayFrac does not reflect this!
if (!boundingBox.ClipLineSegment(ref start, ref end))
{
return(null);
}
// Scale up from (unit) object space to voxel grid resolution
var half = new Vector(0.5, 0.5, 0.5);
start = (start * 0.5 + half) * ((double)GridSize - 0.001);
end = (end * 0.5 + half) * ((double)GridSize - 0.001);
int oldX = -1, oldY = -1, oldZ = -1;
// TODO: a larger minStep (e.g. 1) makes the voxels look like thin squares facing a single direction. Why?
foreach (var pos in LineWalker3D.WalkLine(start, end, 0.1))
{
int x = (int)pos.x;
var y = (int)pos.y;
var z = (int)pos.z;
Contract.Assert(x >= 0 && x < GridSize && y >= 0 && y < GridSize && z >= 0 && z < GridSize);
// TODO: Contracts analyser says pos.z is not -1 here, and similarly for x and y
if (x != oldX && y != oldY && z != oldZ)
{
uint colorSample = voxelColors[x, y, z];
// Treat black voxels as transparent
if (colorSample != 0)
{
//var normal = new Vector(oldX - x, oldY - y, oldZ - z);
//normal.Normalise();
var normal = voxelNormals[x, y, z];
Contract.Assume(normal.IsUnitVector);
// DEBUGGING: visualise normals
//colorSample = new Color(normal.x, normal.y, normal.z).ToARGB();
// TODO: also return correct rayFrac, pos and normal
return(new IntersectionInfo {
color = colorSample, normal = normal /*, pos = pos, rayFrac = (pos - start).Length */
});
//return new IntersectionInfo { color = sample, pos = pos, rayFrac = (pos - start).Length, normal = Vector.Up };
}
}
}
return(null);
}
// Test line walking by drawing lots of 2D lines on a view, to see how they look.
public static void TestLineWalking(Surface view)
{
Contract.Requires(view != null);
const int jump = 10;
for (int col = 0; col < view.Width - 1; col++)
{
view.DrawPixel(col, 0, Color.Pink.ToARGB());
view.DrawPixel(col, view.Height - 1, Color.Pink.ToARGB());
}
for (int col = 0; col < view.Height - 1; col++)
{
view.DrawPixel(0, col, Color.Cyan.ToARGB());
view.DrawPixel(view.Width - 1, col, Color.Cyan.ToARGB());
}
for (int col = 0; col < view.Width / jump; col++)
{
foreach (var pt in LineWalker3D.WalkLine(new Vector(col * jump, 0, 0), new Vector(view.Width / 2, view.Height / 2, 0)))
{
view.DrawPixel((int)(pt.x + 0.5), (int)(pt.y + 0.5), Color.Blue.ToARGB());
}
/*
* foreach (var pt in LineWalker3D.WalkLine(col * jump, view.Height - 1, view.Width / 2, view.Height / 2))
* {
* view.DrawViewPixel((int)(pt.x + 0.5), (int)(pt.y + 0.5), Color.Green.ToARGB());
* }
*/
}
/*
* for (int col = 0; col < view.Height / jump; col++)
* {
* foreach (var pt in LineWalker3D.WalkLine(0, col * jump, view.Width / 2, view.Height / 2))
* {
* view.DrawViewPixel((int)(pt.x + 0.5), (int)(pt.y + 0.5), Color.Red.ToARGB());
* }
*
* foreach (var pt in LineWalker3D.WalkLine(view.Width - 1, col * jump, view.Width / 2, view.Height / 2))
* {
* view.DrawViewPixel((int)(pt.x + 0), (int)(pt.y + 0), Color.Yellow.ToARGB());
* }
* }
*/
//for (int row = 0; row < view.Height; row++)
//{
// for (int col = 0; col < view.Width; col++)
// {
// Vector start = new Vector(mouseViewPos.x, mouseViewPos.y);
// Vector end = new Vector(col, row);
// var hitPt = map.IntersectWorldLine(start, end, 1);
// var color = hitPt.IsInvalid() ? Color.Red : Color.Green;
// //var color = map.IsSolidTile(col, row) ? Color.Red : Color.Green;
// view.DrawViewPixel(col, row, color.ToARGB());
// }
//}
}