static unsafe void GetVoxelsInternal(ref GetVoxelsContext context, int indexStart)
{
int i0 = context.indices[indexStart];
int i1 = context.indices[indexStart + 1];
int i2 = context.indices[indexStart + 2];
SimpleMesh.Vertex v0 = context.verts[i0];
SimpleMesh.Vertex v1 = context.verts[i1];
SimpleMesh.Vertex v2 = context.verts[i2];
float3 a = v0.Position;
float3 b = v1.Position;
float3 c = v2.Position;
float3 normalTri;
{
float3 normalCross = cross(b - a, c - a);
float normalCrossLengthSqrd = dot(normalCross, normalCross);
if (normalCrossLengthSqrd == 0f)
{
return;
}
normalTri = normalCross * rcp(sqrt(normalCrossLengthSqrd));
}
// extend every tri by half a voxel by just extending it along the corner-middle dir.
// it's a naive attempt to get a conservative rasterizer - works good enough in general
float3 middle = (a + b + c) / 3f;
a += normalize(a - middle) * 0.5f;
b += normalize(b - middle) * 0.5f;
c += normalize(c - middle) * 0.5f;
// get the AABB
float3 minf = min(a, min(b, c));
float3 maxf = max(a, max(b, c));
int3 maxDimensions = context.maxDimensions;
int3 mini = clamp(int3(floor(minf)), 0, maxDimensions);
int3 maxi = clamp(int3(ceil(maxf)), 0, maxDimensions);
int written = 0;
VoxelizedPosition *positions = context.positions;
int positionsLength = context.positionLength;
Color color0 = v0.Color;
Color color1 = v1.Color;
Color color2 = v2.Color;
for (int x = mini.x; x <= maxi.x; x++)
{
for (int z = mini.z; z <= maxi.z; z++)
{
for (int y = mini.y; y <= maxi.y; y++)
{
float3 voxel = float3(x, y, z) + 0.5f;
float normalDistToTriangle = dot(voxel - a, normalTri);
if (abs(normalDistToTriangle) > 0.5f)
{
continue; // distance to the triangle plane is over half a voxel -> the other side will have a voxel instead if we're at 0.5-1.0 dist
}
// set up barycentric coordinates
float3 p = voxel - normalTri * normalDistToTriangle;
float3 p0 = b - a;
float3 p1 = c - a;
float3 p2 = p - a;
float d00 = dot(p0, p0);
float d01 = dot(p0, p1);
float d11 = dot(p1, p1);
float d20 = dot(p2, p0);
float d21 = dot(p2, p1);
float denom = 1f / (d00 * d11 - d01 * d01);
float3 barry;
barry.y = (d11 * d20 - d01 * d21) * denom; // v1
barry.z = (d00 * d21 - d01 * d20) * denom; // v2
barry.x = 1.0f - barry.y - barry.z; // v0
if (any(barry < 0 | barry > 1))
{
continue; // we're on the triangle plane, but outside the triangle
}
// interpolate vertex colors with the barycentric coordinates
Color color;
color.r = (color0.r * barry.x + color1.r * barry.y + color2.r * barry.z);
color.g = (color0.g * barry.x + color1.g * barry.y + color2.g * barry.z);
color.b = (color0.b * barry.x + color1.b * barry.y + color2.b * barry.z);
color.a = 1f;
float2 uv;
uv.x = (v0.UV.x * barry.x + v1.UV.x * barry.y + v2.UV.x * barry.z);
uv.y = (v0.UV.y * barry.x + v1.UV.y * barry.y + v2.UV.y * barry.z);
int idx = x * (maxDimensions.z + 1) + z;
positions[written++] = new VoxelizedPosition
{
XZIndex = idx,
Y = (short)y,
Color = color,
MaterialIndex = (sbyte)v0.MaterialIndex,
UV = uv
};
if (written == positionsLength)
{
goto END; // buffer full, our triangle must've been huge
}
}
}
}
END:
context.writtenVoxelCount = written;
}
public unsafe static void GetVoxels(ref GetVoxelsContext context, int indexStart)
{
GetVoxelsInvoker(ref context, indexStart);
}
