// 在p1处开始画, p2p3是水平线, yStep为-1表示往下
void DrawTriangleInner(MyShaderBase obj, ShaderParameters shaderParams, ShaderSemantic p1, ShaderSemantic p2, ShaderSemantic p3, int yStep)
{
float x1 = p1.SV_POSITION.x;
int y1 = (int)p1.SV_POSITION.y;
float x2 = p2.SV_POSITION.x;
int y2 = (int)p2.SV_POSITION.y;
float x3 = p3.SV_POSITION.x;
float y3 = p3.SV_POSITION.y;
float m1 = (y1 - y2) / (x1 - x2); // 直线p1p2: y - y1 = m1*(x - x1), m1 = (y1-y2)/(x1-x2)
float m2 = (y1 - y3) / (x1 - x3); // 直线p1p3: y - y1 = m2*(x - x1), m2 = (y1-y3)/(x1-x3)
var type = p1.GetType();
for (int y = y1; y != y2;)
{
// scan line
float xl = (y - y1) / m1 + x1;
float leftWeight = (xl - x1) / (x2 - x1);
ShaderSemantic left = ShaderSemantic.CreateInstance(type);
left.Lerp(p1, p2, leftWeight);
float xr = (y - y1) / m2 + x1;
float rightWeight = (xr - x1) / (x3 - x1);
ShaderSemantic right = ShaderSemantic.CreateInstance(type);
right.Lerp(p1, p3, Mathf.Abs(rightWeight));
DrawLine(obj, shaderParams, left, right);
y += yStep;
}
}
void DrawLine(MyShaderBase obj, ShaderParameters shaderParams, ShaderSemantic p1, ShaderSemantic p2)
{
int x1 = (int)p1.SV_POSITION.x;
int y1 = (int)p1.SV_POSITION.y;
int x2 = (int)p2.SV_POSITION.x;
int y2 = (int)p2.SV_POSITION.y;
// 令x1 < x2 && 0 < abs(dy) < dx
bool isSteep = Mathf.Abs(y2 - y1) > Mathf.Abs(x2 - x1);
if (isSteep)
{
MyUtility.Swap(ref x1, ref y1);
MyUtility.Swap(ref x2, ref y2);
}
if (x1 > x2)
{
MyUtility.Swap(ref x1, ref x2);
MyUtility.Swap(ref y1, ref y2);
}
int dy = System.Math.Abs(y2 - y1);
int dx = x2 - x1;
if (dy == 0 && dx == 0)
{
return;
}
int slope_err = dy - dx;
int ystep = (y1 < y2) ? 1 : -1;
var type = p1.GetType();
for (int x = x1, y = y1; x <= x2; x++)
{
int _x = isSteep ? y : x;
int _y = isSteep ? x : y;
if (_x > 0 && _x < tex.width && _y > 0 && _y < tex.height)
{
ShaderSemantic v2f = ShaderSemantic.CreateInstance(type);
float w = ((float)x - x1) / (x1 - x2);
v2f.Lerp(p1, p2, Mathf.Abs(w));
var color = obj.PixelShader(v2f, shaderParams);
renderBuffer.Update(obj, _x, _y, v2f, color);
}
slope_err += dy;
if (slope_err >= 0)
{
slope_err -= dx;
y += ystep;
}
}
}
void DrawCall(MyShaderBase obj, Mesh mesh)
{
var vertices = mesh.vertices;
var triangles = mesh.triangles;
float screenWidth = MyCamera.pixelWidth;
float screenHeight = MyCamera.pixelHeight;
var far = MyCamera.farClipPlane;
var near = MyCamera.nearClipPlane;
float w = screenWidth / 2;
float h = screenHeight / 2;
var shaderParams = new ShaderParameters(obj.transform, MyCamera);
ShaderSemantic[] appFullData = new ShaderSemantic[vertices.Length];
for (int i = 0; i < vertices.Length; i++)
{
var appdata = (ShaderSemantic)System.Activator.CreateInstance(obj.CastType);
var p = vertices[i];
appdata.POSITION = new Vector4(p.x, p.y, p.z, 1);
appdata.NORMAL = mesh.normals[i];
appdata.TANGENT = mesh.tangents[i];
appdata.TEXCOORD0 = mesh.uv[i];
appFullData[i] = appdata;
}
// vertex shader
for (int i = 0; i < vertices.Length; i++)
{
var appdata = appFullData[i];
// vertex shader: local space -> world space -> view space -> clip space
ShaderSemantic v2f = obj.VertexShader(appdata, shaderParams);
var p = v2f.SV_POSITION;
// homogeneous divide: clip space -> NDC[-1, 1]
p = new Vector4(p.x / p.w, p.y / p.w, p.z / p.w, 1);
v2f.POSITION = p;
// NDC -> screen space (window space) https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-semantics?redirectedfrom=MSDN#direct3d-9-vpos-and-direct3d-10-sv_position
v2f.SV_POSITION = new Vector3(p.x * w + w, p.y * h + h, (far - near) * p.z / 2 + (far + near) / 2);
appFullData[i] = v2f;
}
// pixel shader
if (shadingMode == ShadingMode.Wireframe)
{
Wireframe(obj, shaderParams, mesh, appFullData); // Wireframe
}
else
{
Shaded(obj, shaderParams, mesh, appFullData); // Shaded
}
}
void DrawTriangle(MyShaderBase obj, ShaderParameters shaderParams, ShaderSemantic p1, ShaderSemantic p2, ShaderSemantic p3)
{
// 令 y1 ≥ y2 ≥ y3
if (p2.SV_POSITION.y <= p3.SV_POSITION.y)
{
MyUtility.Swap(ref p2, ref p3);
}
if (p1.SV_POSITION.y <= p2.SV_POSITION.y)
{
MyUtility.Swap(ref p2, ref p1);
}
if (p2.SV_POSITION.y < p3.SV_POSITION.y)
{
MyUtility.Swap(ref p2, ref p3);
}
float y1 = p1.SV_POSITION.y; // A.y
float y3 = p3.SV_POSITION.y; // C.y
/* 将三角形在B点水平x轴切开上下两部分分开画：
* BM为水平直线, M在AC线上
* 直线AC: y - y1 = m * (x - x1), 其中m = (y1-y3) / (x1-x3)
* 将xy互换: x - x1 = m * (y - y1), 其中m = (x1-x3) / (y1-y3)
* 已知: B.y == M.y(M_y), 求M.x 即(M_x)
* 得: x = m * (y - y1) + x1
*/
float M_y = p2.SV_POSITION.y;
ShaderSemantic M = ShaderSemantic.CreateInstance(p1.GetType());
float w = (M_y - y1) / (y3 - y1);
M.Lerp(p1, p3, Mathf.Abs(w));
// B和M的顺序 由x坐标确定
ShaderSemantic Left = p2.SV_POSITION.x < M.SV_POSITION.x ? p2 : M;
ShaderSemantic Right = p2.SV_POSITION.x < M.SV_POSITION.x ? M : p2;
DrawTriangleInner(obj, shaderParams, p1, Left, Right, -1); // draw 🔺ABM
DrawTriangleInner(obj, shaderParams, p3, Left, Right, +1); // draw 🔺CBM
DrawLine(obj, shaderParams, Left, Right); // draw line BM
// debug
/*
* DrawPoint((int)p1.SV_POSITION.x, (int)p1.SV_POSITION.y, p1.COLOR);
* DrawPoint((int)p3.SV_POSITION.x, (int)p3.SV_POSITION.y, p3.COLOR);
* DrawPoint((int)M.SV_POSITION.x, (int)M.SV_POSITION.y, M.COLOR);
* DrawPoint((int)p2.SV_POSITION.x, (int)p2.SV_POSITION.y, p2.COLOR);
*/
}
void Wireframe(MyShaderBase obj, ShaderParameters shaderParams, Mesh mesh, ShaderSemantic[] appFullData)
{
var triangles = mesh.triangles;
ShaderSemantic last = null;
for (int i = 0; i < triangles.Length; i++)
{
var v2f = appFullData[triangles[i]];
v2f.COLOR = Color.white;
if (i > 0 && i % 3 != 0)
{
DrawLine(obj, shaderParams, last, v2f);
}
last = v2f;
}
}
void Shaded(MyShaderBase obj, ShaderParameters shaderParams, Mesh mesh, ShaderSemantic[] appFullData)
{
var triangles = mesh.triangles;
for (int i = 0; i < triangles.Length; i += 3)
{
ShaderSemantic p1 = appFullData[triangles[i]];
ShaderSemantic p2 = appFullData[triangles[i + 1]];
ShaderSemantic p3 = appFullData[triangles[i + 2]];
//outline debug
//DrawLine(obj, shaderParams, p1, p2);
//DrawLine(obj, shaderParams, p2, p3);
//DrawLine(obj, shaderParams, p3, p1);
// debug color
p1.COLOR = Color.red;
p2.COLOR = Color.green;
p3.COLOR = Color.blue;
DrawTriangle(obj, shaderParams, p1, p2, p3);
//break; // debug
}
}
public void Update(MyShaderBase obj, int x, int y, ShaderSemantic v2f, Color outputColor)
{
if (!DepthTest(x, y, v2f))
{
return;
}
var newDepth = v2f.POSITION.z;
var oldDepth = GetDepth(x, y);
switch (obj.Commands.ZWrite)
{
case ZWrite.On:
switch (obj.Commands.ZTest)
{
case ZTest.Less:
if (newDepth < oldDepth)
{
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
}
break;
case ZTest.LEqual:
if (newDepth <= oldDepth)
{
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
}
break;
case ZTest.Equal:
if (newDepth == oldDepth)
{
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
}
break;
case ZTest.GEqual:
if (newDepth >= oldDepth)
{
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
}
break;
case ZTest.Greater:
if (newDepth > oldDepth)
{
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
}
break;
case ZTest.NotEqual:
if (newDepth != oldDepth)
{
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
}
break;
case ZTest.Always:
SetDepth(x, y, newDepth);
SetColor(x, y, outputColor);
break;
}
break;
case ZWrite.Off:
break;
default:
break;
}
}