public static void DrawDDALine(Vertex2D p1, Vertex2D p2, AddPixelHandler handler, ZTestHandler zTest)
{
var dist = (p1 - p2).Length2D;
// 如果长度小于2像素就只是一个点;
if (dist < 2)
{
if (null != zTest && !zTest(p1.x, p1.y, p1.depth))
{
return;
}
handler?.Invoke(p1.x, p1.y, p1.depth, p1.color);
return;
}
// 绘制中心点;
Vertex2D center = p1 + (p2 - p1) / 2;
float depth = MathUtil.Interpolate(p1.depth, center.depth, 0.5f);
if (null != zTest && !zTest(center.x, center.y, depth))
{
return;
}
// 颜色线性插值;
Color clr = Color.FromArgb(
(p1.color.a + p2.color.a) * 0.5f,
(p1.color.r + p2.color.r) * 0.5f,
(p1.color.g + p2.color.g) * 0.5f,
(p1.color.b + p2.color.b) * 0.5f);
if (null != handler)
{
handler(center.x, center.y, MathUtil.Interpolate(p1.depth, center.depth, 0.5f), clr);
}
// 前半段递归;
DrawDDALine(p1, center, handler, zTest);
// 后半段递归;
DrawDDALine(center, p2, handler, zTest);
}
public static void DrawBresenhamLine(Vertex2D p1, Vertex2D p2, AddPixelHandler handler, ZTestHandler zTest)
{
// Bresenham’s line algorithm;
int x1 = p1.x;
int y1 = p1.y;
int x2 = p2.x;
int y2 = p2.y;
var dx = Math.Abs(x2 - x1);
var dy = Math.Abs(y2 - y1);
var sx = (x1 < x2) ? 1 : -1;
var sy = (y1 < y2) ? 1 : -1;
var err = dx - dy;
float totalLen = (p1 - p2).SqrLength2D;
if (totalLen <= 0f)
{
return;
}
float invTotalLen = 1f / totalLen;
float p1x = p1.x;
float p1y = p1.y;
float p1d = p1.depth;
float p2d = p2.depth;
Color p1c = p1.color;
Color p2c = p2.color;
while (true)
{
float p1x1 = p1x - x1;
float p1y1 = p1y - y1;
float len = p1x1 * p1x1 + p1y1 * p1y1;
float ratio = len * invTotalLen; // MathUtil.Clamp(len / totalLen);
ratio = ratio < 0 ? 0 : ratio;
ratio = ratio > 1 ? 1 : ratio;
float z1 = p1d + (p2d - p1d) * ratio; //MathUtil.Interpolate(p1.Depth, p2.Depth, ratio);
if (null != zTest && zTest(x1, y1, z1))
{
float a = p1c.a * ratio + p2c.a * (1f - ratio);
float r = p1c.r * ratio + p2c.r * (1f - ratio);
float g = p1c.g * ratio + p2c.g * (1f - ratio);
float b = p1c.b * ratio + p2c.b * (1f - ratio);
Color clr = Color.FromArgb(a, r, g, b);
if (null != handler)
{
handler(x1, y1, z1, clr);
}
}
if ((x1 == x2) && (y1 == y2))
{
break;
}
int e2 = 2 * err;
if (e2 > -dy)
{
err -= dy;
x1 += sx;
}
if (e2 < dx)
{
err += dx;
y1 += sy;
}
}
}
public static void DrawLine(Vertex2D p1, Vertex2D p2, AddPixelHandler handler, DrawLineType drawType, ZTestHandler zTest)
{
switch (drawType)
{
case DrawLineType.DDA:
DrawDDALine(p1, p2, handler, zTest);
break;
case DrawLineType.Bresenham:
DrawBresenhamLine(p1, p2, handler, zTest);
break;
}
}