public void FillTriangle(Vertex v1, Vertex v2, Vertex v3)
{
var verts = SortVertex(v1, v2, v3);
if (MathUtility.IsEqual(verts[1].pos.y, verts[2].pos.y))
{
FillBottomFlatTriangle(verts[0], verts[1], verts[2]);
}
else if (verts[0].pos.y == verts[1].pos.y)
{
FillTopFlatTriangle(verts[0], verts[1], verts[2]);
}
else //将三角面切割成平顶平底两个三角面绘制
{
float t = (verts[1].pos.y - verts[0].pos.y) / (verts[2].pos.y - verts[0].pos.y);
Vertex v4 = TransformUtility.LerpVertexInScreenSpace(verts[0], verts[2], t);
v4.color = ColorUtility.Lerp(verts[0], verts[1], verts[2], v4);
float y = verts[1].pos.y;
float x = (int)(verts[0].pos.x + (((float)verts[1].pos.y - verts[0].pos.y) / ((float)verts[2].pos.y - verts[0].pos.y)) *
(verts[2].pos.x - verts[0].pos.x));
v4.pos = new Vector(x, y, verts[1].pos.z);
FillBottomFlatTriangle(verts[0], verts[1], v4);
FillTopFlatTriangle(verts[1], v4, verts[2]);
//测试用
//DrawTriangleLine(v1.pos, v2.pos, v3.pos, Color.Black);
}
}
//v1为最高点
public void FillBottomFlatTriangle(Vertex v1, Vertex v2, Vertex v3)
{
Vertex topVert = v1;
Vertex leftBottomVert = v2.pos.x < v3.pos.x ? v2 : v3;
Vertex rightBottomVert = v2.pos.x > v3.pos.x ? v2 : v3;
Vector p1 = v1.pos;
Vector p2 = leftBottomVert.pos;
Vector p3 = rightBottomVert.pos;
float invSlope1 = (p2.x - p1.x) / (p2.y - p1.y);
float invSlope2 = (p3.x - p1.x) / (p3.y - p1.y);
float onePerLength = 1 / (p2.y - p1.y);
float curX1 = p1.x;
float curX2 = p1.x;
Color top = v1.color;
Color leftBottom = leftBottomVert.color;
Color rightBottom = rightBottomVert.color;
//屏幕原点在左上，所以是Y++不是--
for (int scanLineY = (int)p1.y; scanLineY <= p2.y; scanLineY++)
{
float t = (p2.y - scanLineY) * onePerLength;
Vertex right = TransformUtility.LerpVertexInScreenSpace(rightBottomVert, topVert, t);
Vertex left = TransformUtility.LerpVertexInScreenSpace(leftBottomVert, topVert, t);
if (Application.RenderType == RenderType.VertexColor)
{
DrawScanLine((int)curX1, (int)curX2, scanLineY, left.color, right.color);
}
else if (Application.RenderType == RenderType.Texture)
{
DrawScanLine(left, right);
}
//避免绘制非常窄的三角形时线段出界
if ((invSlope1 < 0 && curX1 + invSlope1 >= p2.x) || (invSlope1 > 0 && curX1 + invSlope1 <= p2.x))
{
curX1 += invSlope1;
}
if ((invSlope2 < 0 && curX2 + invSlope2 >= p3.x) || (invSlope2 > 0 && curX2 + invSlope2 <= p3.x))
{
curX2 += invSlope2;
}
}
}
// v1为左上，v2为右上，v3为最低点
public void FillTopFlatTriangle(Vertex v1, Vertex v2, Vertex v3)
{
Vertex bottomVert = v3;
Vertex leftTopVert = v1.pos.x < v2.pos.x ? v1 : v2;
Vertex rightTopVert = v1.pos.x > v2.pos.x ? v1 : v2;
Vector p1 = leftTopVert.pos;
Vector p2 = rightTopVert.pos;
Vector p3 = v3.pos;
float invSlope1 = (p3.x - p1.x) / (p3.y - p1.y);
float invSlope2 = (p3.x - p2.x) / (p3.y - p2.y);
float onePerLength = 1 / (p3.y - p1.y);
float curX1 = p3.x;
float curX2 = p3.x;
Color bottom = v3.color;
Color leftTop = leftTopVert.color;
Color rightTop = rightTopVert.color;
for (int scanLineY = (int)p3.y; scanLineY >= p2.y; scanLineY--)
{
float t = (scanLineY - p1.y) * onePerLength;
Vertex left = TransformUtility.LerpVertexInScreenSpace(leftTopVert, bottomVert, t);
Vertex right = TransformUtility.LerpVertexInScreenSpace(rightTopVert, bottomVert, t);
if (Application.RenderType == RenderType.VertexColor)
{
DrawScanLine((int)curX1, (int)curX2, scanLineY, left.color, right.color);
}
else if (Application.RenderType == RenderType.Texture)
{
DrawScanLine(left, right);
}
if ((invSlope1 > 0 && curX1 - invSlope1 >= p1.x) || (invSlope1 < 0 && curX1 - invSlope1 <= p1.x))
{
curX1 -= invSlope1;
}
if ((invSlope2 < 0 && curX2 - invSlope2 <= p2.x) || (invSlope2 > 0 && curX2 - invSlope2 >= p2.x))
{
curX2 -= invSlope2;
}
}
}
public override void Render()
{
if (mesh == null)
{
return;
}
Vertex[] tempVerts = new Vertex[] { new Vertex(), new Vertex(), new Vertex() };
int length = mesh.Surfaces.Length;
for (int i = 0; i < length; i++)
{
var surface = mesh.Surfaces[i];
//不把变换后的结果保存顶点中，否则下次渲染顶点位置就不对了
tempVerts[0].Copy(mesh.Vertices[surface.A]);
tempVerts[1].Copy(mesh.Vertices[surface.B]);
tempVerts[2].Copy(mesh.Vertices[surface.C]);
Vector v1 = tempVerts[0].pos;
Vector v2 = tempVerts[1].pos;
Vector v3 = tempVerts[2].pos;
//Obj -> World
Vector wp1 = transform.ApplyObj2World(v1);
Vector wp2 = transform.ApplyObj2World(v2);
Vector wp3 = transform.ApplyObj2World(v3);
//World -> view
Vector vp1 = transform.ApplyWorldToView(wp1);
Vector vp2 = transform.ApplyWorldToView(wp2);
Vector vp3 = transform.ApplyWorldToView(wp3);
//背面消隐
if (TransformUtility.IsBackCulling(vp1, vp2, vp3))
{
continue;
}
//view -> 齐次裁剪空间
Vector cp1 = transform.ApplyViewToClip(vp1);
Vector cp2 = transform.ApplyViewToClip(vp2);
Vector cp3 = transform.ApplyViewToClip(vp3);
// CVV裁剪
//if(...)
//变换到齐次裁剪空间后，w值保存view空间下的z信息
//保存 1/z 用于后面求u'、v'
tempVerts[0].onePerZ = 1 / cp1.w;
tempVerts[1].onePerZ = 1 / cp2.w;
tempVerts[2].onePerZ = 1 / cp3.w;
tempVerts[0].u *= tempVerts[0].onePerZ;
tempVerts[0].v *= tempVerts[0].onePerZ;
tempVerts[1].u *= tempVerts[1].onePerZ;
tempVerts[1].v *= tempVerts[1].onePerZ;
tempVerts[2].u *= tempVerts[2].onePerZ;
tempVerts[2].v *= tempVerts[2].onePerZ;
//透视除法 齐次裁剪空间 -> NDC空间
cp1 /= cp1.w;
cp2 /= cp2.w;
cp3 /= cp3.w;
//屏幕映射 NDC空间下 -> 屏幕空间
Vector sp1 = Screen.ComputeToScreenPos(cp1);
Vector sp2 = Screen.ComputeToScreenPos(cp2);
Vector sp3 = Screen.ComputeToScreenPos(cp3);
tempVerts[0].pos = sp1;
tempVerts[1].pos = sp2;
tempVerts[2].pos = sp3;
switch (Application.RenderType)
{
case RenderType.Wireframe:
graphics.DrawTriangleLine(tempVerts[0].pos, tempVerts[1].pos, tempVerts[2].pos, Color.Red);
break;
case RenderType.Fill:
graphics.FillTriangle(tempVerts[0].pos, tempVerts[1].pos, tempVerts[2].pos, Color.Red);
break;
case RenderType.VertexColor:
graphics.FillTriangle(tempVerts[0], tempVerts[1], tempVerts[2]);
break;
case RenderType.Texture:
graphics.FillTriangle(tempVerts[0], tempVerts[1], tempVerts[2]);
break;
}
}
}