Ghetty-Engine/algorithms.txt at main · SamuelScerri/Ghetty-Engine · GitHub

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func (tile *Tile) SweepLine(triangle *ProcessedTriangle) {
	var invSlope1 float32 = (triangle.Triangle.Vertices[1][X] - triangle.Triangle.Vertices[0][X]) /
		(triangle.Triangle.Vertices[1][Y] - triangle.Triangle.Vertices[0][Y])

	var invSlope2 float32 = (triangle.Split - triangle.Triangle.Vertices[0][X]) /
		(triangle.Triangle.Vertices[1][Y] - triangle.Triangle.Vertices[0][Y])

	var clampedUp float32 = Clamp(triangle.Triangle.Vertices[0][Y], tile.Y, tile.Y+TileYSize)
	var clampedMiddle float32 = Clamp(triangle.Triangle.Vertices[1][Y], tile.Y, tile.Y+TileYSize)
	var clampedDown float32 = Clamp(triangle.Triangle.Vertices[2][Y], tile.Y, tile.Y+TileYSize)

	var difference float32 = clampedUp - triangle.Triangle.Vertices[0][Y]
	var curX1, curX2 float32 = triangle.Triangle.Vertices[0][X] + invSlope1*difference,
		triangle.Triangle.Vertices[0][X] + invSlope2*difference

	for y := int(clampedUp); y < int(clampedMiddle); y++ {
		var clampedLeft, clampedRight int = int(Clamp(curX1, tile.X, tile.X+TileXSize)),
			int(Clamp(curX2, tile.X, tile.X+TileXSize))

		for x := clampedLeft; x < clampedRight; x++ {
			//var w, s, t float32 = triangle.Barycentric(x, y)
		}

		curX1 += invSlope1
		curX2 += invSlope2
	}

	invSlope1 = (triangle.Triangle.Vertices[2][X] - triangle.Triangle.Vertices[1][X]) /
		(triangle.Triangle.Vertices[2][Y] - triangle.Triangle.Vertices[1][Y])

	invSlope2 = (triangle.Triangle.Vertices[2][X] - triangle.Split) /
		(triangle.Triangle.Vertices[2][Y] - triangle.Triangle.Vertices[1][Y])

	difference = triangle.Triangle.Vertices[2][Y] - clampedDown
	curX1, curX2 = triangle.Triangle.Vertices[2][X]-invSlope1*difference, triangle.Triangle.Vertices[2][X]-invSlope2*difference

	for y := int(clampedDown) - 1; y > int(clampedMiddle)-1; y-- {
		var clampedLeft, clampedRight int = int(Clamp(curX1, tile.X, tile.X+TileXSize)),
			int(Clamp(curX2, tile.X, tile.X+TileXSize))

		for x := clampedLeft; x < clampedRight; x++ {
			var w, s, t float32 = triangle.Barycentric(x, y)
			var depth float32 = w*triangle.Triangle.Vertices[0][Z] + s*triangle.Triangle.Vertices[1][Z] + t*triangle.Triangle.Vertices[2][Z]

			if position := tile.ConvertPosition(x, y); depth < tile.Depth[position] {

				if triangle.Triangle.Texture == nil {
					//var r, g, b float32 = triangle.Triangle.Shader(triangle.Triangle.Interpolate(w, s, t))
					//tile.Set(position, byte(r*255), byte(g*255), byte(b*255), depth)
				} else {
					var wt float32 = 1 / (w*triangle.Triangle.UV[0][Z] + s*triangle.Triangle.UV[1][Z] + t*triangle.Triangle.UV[2][Z])

					var uv Vertex = Vertex{
						(w*triangle.Triangle.UV[0][X] + s*triangle.Triangle.UV[1][X] + t*triangle.Triangle.UV[2][X]) * wt,
						(w*triangle.Triangle.UV[0][Y] + s*triangle.Triangle.UV[1][Y] + t*triangle.Triangle.UV[2][Y]) * wt,
					}

					var r, g, b float32 = triangle.Triangle.Interpolate(w, s, t)
					triangle.Triangle.Shader.Fragment(&r, &g, &b, &uv, &Brick)

					tile.Set(position, byte(r*255), byte(g*255), byte(b*255), depth)
				}

			}
		}

		curX1 -= invSlope1
		curX2 -= invSlope2
	}
}