public static void DrawTriangle(Vertex v1, Vertex v2, Vertex v3, Color color, Texture texture)
{
if (v1.Coordinates.y > v2.Coordinates.y)
{
var temp = v2;
v2 = v1;
v1 = temp;
}
if (v2.Coordinates.y > v3.Coordinates.y)
{
var temp = v2;
v2 = v3;
v3 = temp;
}
if (v1.Coordinates.y > v2.Coordinates.y)
{
var temp = v2;
v2 = v1;
v1 = temp;
}
Vector3d p1 = v1.Coordinates;
Vector3d p2 = v2.Coordinates;
Vector3d p3 = v3.Coordinates;
Vector3d lightPos = new Vector3d(-100, 100, 100);
//入射光线和法线的夹角
float nl1 = ComputeNDotL(v1.WorldCoordinates, v1.Normal, lightPos);
float nl2 = ComputeNDotL(v2.WorldCoordinates, v2.Normal, lightPos);
float nl3 = ComputeNDotL(v3.WorldCoordinates, v3.Normal, lightPos);
var data = new ScanLineData {
};
// 反向斜率
float dP1P2, dP1P3;
// 计算反向斜率
if (p2.y - p1.y > 0)
{
dP1P2 = (p2.x - p1.x) / (p2.y - p1.y);
}
else
{
dP1P2 = 0;
}
if (p3.y - p1.y > 0)
{
dP1P3 = (p3.x - p1.x) / (p3.y - p1.y);
}
else
{
dP1P3 = 0;
}
// 对于第一种情况来说，三角形是这样的：
// P1
// -
// --
// - -
// - -
// - - P2
// - -
// - -
// -
// P3
if (dP1P2 > dP1P3)
{
for (var y = (int)p1.y; y <= (int)p3.y; y++)
{
data.currentY = y;
if (y < p2.y)
{
data.ndotla = nl1;
data.ndotlb = nl3;
data.ndotlc = nl1;
data.ndotld = nl2;
data.ua = v1.TextureCoordinates.x;
data.ub = v3.TextureCoordinates.x;
data.uc = v1.TextureCoordinates.x;
data.ud = v2.TextureCoordinates.x;
data.va = v1.TextureCoordinates.y;
data.vb = v3.TextureCoordinates.y;
data.vc = v1.TextureCoordinates.y;
data.vd = v2.TextureCoordinates.y;
ProcessScanLine(data, v1, v3, v1, v2, color, texture);
}
else
{
data.ndotla = nl1;
data.ndotlb = nl3;
data.ndotlc = nl2;
data.ndotld = nl3;
data.ua = v1.TextureCoordinates.x;
data.ub = v3.TextureCoordinates.x;
data.uc = v2.TextureCoordinates.x;
data.ud = v3.TextureCoordinates.x;
data.va = v1.TextureCoordinates.y;
data.vb = v3.TextureCoordinates.y;
data.vc = v2.TextureCoordinates.y;
data.vd = v3.TextureCoordinates.y;
ProcessScanLine(data, v1, v3, v2, v3, color, texture);
}
}
}
// 对于第二种情况来说，三角形是这样的：
// P1
// -
// --
// - -
// - -
// P2 - -
// - -
// - -
// -
// P3
else
{
for (var y = (int)p1.y; y <= (int)p3.y; y++)
{
data.currentY = y;
if (y < p2.y)
{
data.ndotla = nl1;
data.ndotlb = nl2;
data.ndotlc = nl1;
data.ndotld = nl3;
data.ua = v1.TextureCoordinates.x;
data.ub = v2.TextureCoordinates.x;
data.uc = v1.TextureCoordinates.x;
data.ud = v3.TextureCoordinates.x;
data.va = v1.TextureCoordinates.y;
data.vb = v2.TextureCoordinates.y;
data.vc = v1.TextureCoordinates.y;
data.vd = v3.TextureCoordinates.y;
ProcessScanLine(data, v1, v2, v1, v3, color, texture);
}
else
{
data.ndotla = nl2;
data.ndotlb = nl3;
data.ndotlc = nl1;
data.ndotld = nl3;
data.ua = v2.TextureCoordinates.x;
data.ub = v3.TextureCoordinates.x;
data.uc = v1.TextureCoordinates.x;
data.ud = v3.TextureCoordinates.x;
data.va = v2.TextureCoordinates.y;
data.vb = v3.TextureCoordinates.y;
data.vc = v1.TextureCoordinates.y;
data.vd = v3.TextureCoordinates.y;
ProcessScanLine(data, v2, v3, v1, v3, color, texture);
}
}
}
}
// 在两点之间从左到右绘制一条线段
// papb -> pcpd
// pa, pb, pc, pd在之前必须已经排好序
public static void ProcessScanLine(ScanLineData data, Vertex va, Vertex vb, Vertex vc, Vertex vd, Color color, Texture texture)
{
Vector3d pa = va.Coordinates;
Vector3d pb = vb.Coordinates;
Vector3d pc = vc.Coordinates;
Vector3d pd = vd.Coordinates;
// 由当前的y值，我们可以计算出梯度
// 以此再计算出 起始X(sx) 和 结束X(ex)
// 如果pa.Y == pb.Y 或者 pc.Y== pd.y的话，梯度强制为1
var gradient1 = pa.y != pb.y ? (data.currentY - pa.y) / (pb.y - pa.y) : 1;
var gradient2 = pc.y != pd.y ? (data.currentY - pc.y) / (pd.y - pc.y) : 1;
int sx = (int)Common.Interpolate(pa.x, pb.x, gradient1);
int ex = (int)Common.Interpolate(pc.x, pd.x, gradient2);
// 计算 开始Z值 和 结束Z值
float z1 = Common.Interpolate(pa.z, pb.z, gradient1);
float z2 = Common.Interpolate(pc.z, pd.z, gradient2);
// 将法线插值到Y中
var snl = Common.Interpolate(data.ndotla, data.ndotlb, gradient1);
var enl = Common.Interpolate(data.ndotlc, data.ndotld, gradient2);
// 将纹理坐标插值到Y中
var su = Common.Interpolate(data.ua, data.ub, gradient1);
var eu = Common.Interpolate(data.uc, data.ud, gradient2);
var sv = Common.Interpolate(data.va, data.vb, gradient1);
var ev = Common.Interpolate(data.vc, data.vd, gradient2);
// 从左(sx)向右(ex)绘制一条线
for (var x = sx; x < ex; x++)
{
float gradient = (x - sx) / (float)(ex - sx);
var z = Common.Interpolate(z1, z2, gradient);
var ndotl = Common.Interpolate(snl, enl, gradient);
var u = Common.Interpolate(su, eu, gradient);
var v = Common.Interpolate(sv, ev, gradient);
Color textureColor;
if (texture != null)
{
textureColor = texture.Map(u, v);
}
else
{
textureColor = (Color)ColorConverter.ConvertFromString("White");
}
Color blendColor = new Color();
blendColor.ScR = color.ScR * textureColor.ScR * ndotl;
blendColor.ScG = color.ScG * textureColor.ScG * ndotl;
blendColor.ScB = color.ScB * textureColor.ScB * ndotl;
blendColor.ScA = color.ScA * textureColor.ScA * ndotl;
RenderBuffer.Instance.SetPixel3d(x, data.currentY, z, blendColor);
}
}
