bool FrontEndCullingByArea(VSOutput v0, VSOutput v1, VSOutput v2)
{
if (context.frontEndCull == FrontEndCull.Off)
{
return(true);
}
if (context.cullMode == CullMode.None)
{
return(true);
}
//cull back
Vector2 p0 = new Vector2(v0.position.X, v0.position.Y);
Vector2 p1 = new Vector2(v1.position.X, v1.position.Y);
Vector2 p2 = new Vector2(v2.position.X, v2.position.Y);
//做了透射除法,Culling准确点
p0 *= 1 / v0.position.W;
p1 *= 1 / v1.position.W;
p2 *= 1 / v2.position.W;
float area = Rasterizer.EdgeFunction(p0, p1, p2);
//在Clip Space, area >= 0表示顺时针
if (context.winding == Winding.Clockwise)
{
return(area > 0);
}
return(area < 0);
}
public static VSOutput PerspectiveDivide(VSOutput vClip)
{
const float FLT_EPSILON = 1.192092896e-07F; // smallest such that 1.0+FLT_EPSILON != 1.0
if (vClip.position.W <= FLT_EPSILON)
{
return(null);
}
VSOutput vNDC = new VSOutput();
Vector4 position = vClip.position;
float fInvW = 1 / position.W;
position = new Vector4(position.X * fInvW, position.Y * fInvW, position.Z * fInvW, fInvW);
vNDC.position = position;
vNDC.color = vClip.color * fInvW;
vNDC.texcoord = vClip.texcoord * fInvW;
vNDC.normalWorld = vClip.normalWorld * fInvW;
return(vNDC);
}
public void DrawFace(WavefrontObject meshObj, WavefrontFace face, Shader shader)
{
//WavefontFace是一个triangle fan
//可能会有多个三角形;这些三角形共用第一个顶点做v0
if (face.Vertices.Count < 3)
{
Debug.Assert(false);
return;
}
Vertex vertex0 = Vertex.FromWavefrontVertex(meshObj, face.Vertices[0]);
VSOutput vClip0 = shader.VertShader(vertex0);
context.statics.vertexCount += 1;
for (int i = 1; i + 1 < face.Vertices.Count; i += 1)
{
Vertex vertex1 = Vertex.FromWavefrontVertex(meshObj, face.Vertices[i]);
Vertex vertex2 = Vertex.FromWavefrontVertex(meshObj, face.Vertices[i + 1]);
//顶点着色器
VSOutput vClip1 = shader.VertShader(vertex1);
VSOutput vClip2 = shader.VertShader(vertex2);
context.statics.vertexCount += 2;
DrawTriangle(vClip0, vClip1, vClip2);
}
}
static VSOutput ComputeIntersection(VSOutput S, VSOutput E, float ds, float de)
{
float amount = ds / (ds - de);
VSOutput v = VSOutput.Lerp(S, E, amount);
return(v);
}
static List <VSOutput> ClipToPlane(List <VSOutput> inputs, Vector4 plane)
{
List <VSOutput> outputs = new List <VSOutput>();
VSOutput S = inputs.Last();
float ds = Vector4.Dot(plane, S.position);
bool sInside = ds >= 0;
foreach (var E in inputs)
{
float de = Vector4.Dot(plane, E.position);
bool eInside = de >= 0;
if (eInside)
{
if (!sInside)
{
VSOutput C = ComputeIntersection(S, E, ds, de);
outputs.Add(C);
}
outputs.Add(E);
}
else if (sInside)
{
VSOutput C = ComputeIntersection(S, E, ds, de);
outputs.Add(C);
}
//记录为上一个
S = E;
ds = de;
sInside = eInside;
}
return(outputs);
}
} //viewport坐标
//Other Attributes
public void Clone(VSOutput other)
{
this.position = other.position;
this.normalWorld = other.normalWorld;
this.texcoord = other.texcoord;
this.color = other.color;
this.posScreen = other.posScreen;
}
void DrawWireframe(VSOutput v0, VSOutput v1, VSOutput v2)
{
Color col = context.wireframeColor;
//col = Utils.NextWireframeColor();
DrawLine(v0, v1, col);
DrawLine(v1, v2, col);
DrawLine(v2, v0, col);
}
//裁剪前
public void DrawTriangle(VSOutput vClip0, VSOutput vClip1, VSOutput vClip2)
{
//Backface Culling
if (!FrontEndCulling(vClip0, vClip1, vClip2))
{
return;
}
context.statics.triangleCount += 1;
//Clipping
List <VSOutput> inputs = new List <VSOutput> {
vClip0, vClip1, vClip2
};
List <VSOutput> outputs = Clipping.Clip(inputs, context);
//输出结果是trianglefan
if (outputs.Count < 3)
{
//全裁剪掉了
return;
}
//画Triangle Fan
VSOutput v0 = outputs[0];
VSOutput vNDC0 = Rasterizer.PerspectiveDivide(v0);
if (vNDC0 == null)
{
return;
}
VSOutput vScreen0 = rasterizer.ViewportTransform(vNDC0);
for (int i = 1; i + 1 < outputs.Count; i += 1)
{
VSOutput v1 = outputs[i];
VSOutput v2 = outputs[i + 1];
VSOutput vNDC1 = Rasterizer.PerspectiveDivide(v1);
VSOutput vNDC2 = Rasterizer.PerspectiveDivide(v2);
if (vNDC1 == null || vNDC2 == null)
{
continue;
}
VSOutput vScreen1 = rasterizer.ViewportTransform(vNDC1);
VSOutput vScreen2 = rasterizer.ViewportTransform(vNDC2);
//检查Backface
if (i == 1)
{
//由于裁剪前后的三角形都在同一个平面上，所以只要检查第一个就够了
if (!BackfaceCulling(vScreen0, vScreen1, vScreen2))
{
return;
}
}
context.statics.rasterTriCount += 1;
rasterizer.RasterizeTriangle(vScreen0, vScreen1, vScreen2);
}
}
public static VSOutput Lerp(VSOutput A, VSOutput B, float amount)
{
VSOutput C = new VSOutput();
C.position = Vector4.Lerp(A.position, B.position, amount);
C.normalWorld = Vector3.Lerp(A.normalWorld, B.normalWorld, amount);
C.texcoord = Vector2.Lerp(A.texcoord, B.texcoord, amount);
C.color = Vector4.Lerp(A.color, B.color, amount);
C.posScreen = Vector3.Lerp(A.posScreen, B.posScreen, amount);
return(C);
}
public void Test_BarycentricRasterizeTriangle()
{
context.clearColor = Color.White;
Clear();
//假设n = 1, far = 2
//测试光栅化和插值
//第一个三角形,v0红色在中上，v1绿和v2蓝在中间的左右，v0在far plane， v1,v2在near plane
VSOutput v0 = new VSOutput();
v0.position = new Vector4(0f, 1f, 1f, 2f);
v0.color = new Vector4(1f, 0f, 0f, 1f);
VSOutput v1 = new VSOutput();
v1.position = new Vector4(-0.5f, -0.5f, -1f, 1f);
v1.color = new Vector4(0f, 1f, 0f, 1f);
VSOutput v2 = new VSOutput();
v2.position = new Vector4(0.5f, -0.5f, -1f, 1f);
v2.color = new Vector4(0f, 0f, 1f, 1f);
v0 = Rasterizer.PerspectiveDivide(v0);
v0 = rasterizer.ViewportTransform(v0);
v1 = Rasterizer.PerspectiveDivide(v1);
v1 = rasterizer.ViewportTransform(v1);
v2 = Rasterizer.PerspectiveDivide(v2);
v2 = rasterizer.ViewportTransform(v2);
rasterizer.BarycentricRasterizeTriangle(v0, v1, v2);
//测试depth test
//第二个三角形，v0红在近平面，v1,v2在远
v0.position = new Vector4(-0.5f, 0.5f, -1f, 1f);
v1.position = new Vector4(-2f, -1f, 1f, 2f);
v2.position = new Vector4(0f, -2f, 1f, 2f);
v0 = Rasterizer.PerspectiveDivide(v0);
v0 = rasterizer.ViewportTransform(v0);
v1 = Rasterizer.PerspectiveDivide(v1);
v1 = rasterizer.ViewportTransform(v1);
v2 = Rasterizer.PerspectiveDivide(v2);
v2 = rasterizer.ViewportTransform(v2);
rasterizer.BarycentricRasterizeTriangle(v0, v1, v2);
//第三个三角形，v1绿在近，其他在远平面
v0.position = new Vector4(-2f, 0f, 1f, 2f);
v1.position = new Vector4(-0.5f, -1f, -1f, 1f);
v2.position = new Vector4(0f, -1f, 1f, 2f);
v0 = Rasterizer.PerspectiveDivide(v0);
v0 = rasterizer.ViewportTransform(v0);
v1 = Rasterizer.PerspectiveDivide(v1);
v1 = rasterizer.ViewportTransform(v1);
v2 = Rasterizer.PerspectiveDivide(v2);
v2 = rasterizer.ViewportTransform(v2);
rasterizer.BarycentricRasterizeTriangle(v0, v1, v2);
}
public void DrawLine(VSOutput v0, VSOutput v1, Color color)
{
Vector2 p0 = new Vector2(v0.posScreen.X, v0.posScreen.Y);
Vector2 p1 = new Vector2(v1.posScreen.X, v1.posScreen.Y);
bool accept = CohenSutherlandLineClip(ref p0, ref p1);
if (!accept)
{
return;
}
BresenhamDrawLine(p0, p1, color);
}
public VSOutput VertShader(Vertex v)
{
VSOutput OUT = new VSOutput();
OUT.position = Vector4.Transform(v.position, MVP);
Vector4 normalWorld = Vector4.Transform(v.normal, Matrix4x4.Transpose(worldToModel));
OUT.normalWorld = new Vector3(normalWorld.X, normalWorld.Y, normalWorld.Z);
OUT.texcoord = v.texcoord;
OUT.color = v.color;
return(OUT);
}
public void RasterizeTriangle(VSOutput vScreen0, VSOutput vScreen1, VSOutput vScreen2)
{
switch (context.drawMode)
{
case DrawMode.Normal:
case DrawMode.Depth:
BarycentricRasterizeTriangle(vScreen0, vScreen1, vScreen2);
break;
case DrawMode.Wireframe:
DrawWireframe(vScreen0, vScreen1, vScreen2);
break;
}
}
public VSOutput ViewportTransform(VSOutput vNDC)
{
VSOutput vScreen = new VSOutput();
vScreen.Clone(vNDC);
int width = context.frameBuffer.Width;
int height = context.frameBuffer.Height;
float x = (vNDC.position.X + 1) * 0.5f;
float y = (1 - vNDC.position.Y) * 0.5f;
//把z从[-1,1]转到[0,1]
float z = (vNDC.position.Z + 1) * 0.5f;
vScreen.posScreen = new Vector3(x * width, y * height, z);
return(vScreen);
}
public void TestClipping()
{
Clear();
context.clippingMode = ClippingMode.SixPlane;
//context.clippingMode = ClippingMode.Off;
context.drawMode = DrawMode.Wireframe;
context.cullMode = CullMode.Back;
context.frontEndCull = FrontEndCull.Off;
VSOutput v0 = new VSOutput();
VSOutput v1 = new VSOutput();
VSOutput v2 = new VSOutput();
List <VSOutput> inputs = new List <VSOutput>()
{
v0, v1, v2
};
//第一个三角形，右裁剪平面，一个顶点在外=>生成两个三角形
v0.position = new Vector4(0.5f, 0.5f, 0, 1);
v1.position = new Vector4(0, -0.5f, 0, 1);
v2.position = new Vector4(2, 0, 0, 1);//在外面
DrawTriangle(v0, v1, v2);
//第二个三角形，上裁剪平面，两个顶点在外=>生成一个三角形
v0.position = new Vector4(-0.5f, 4f, 0, 1);
v1.position = new Vector4(0.5f, 0f, 0, 1); //在外面
v2.position = new Vector4(0.6f, 2f, 0, 1); //在外面
DrawTriangle(v0, v1, v2);
//第三个，三个顶点都在外
v0.position = new Vector4(0.6f, 1.5f, 0, 1);
v1.position = new Vector4(-1.5f, -0.3f, 0, 1);
v2.position = new Vector4(0.8f, -1.2f, 0, 1);
DrawTriangle(v0, v1, v2);
//顺别测下Back face Culling;对换了v1和v2，应该不画
v0.position = new Vector4(0.6f, 1.5f, 0, 1);
v2.position = new Vector4(-1.5f, -0.3f, 0, 1);
v1.position = new Vector4(0.8f, -1.2f, 0, 1);
//DrawTriangle(v0, v1, v2);
Present();
}
public PSOutput FragShader(VSOutput v)
{
//invert uv
if (shaderContext.invertTexture)
{
//v.texcoord = new Vector2(1 - v.texcoord.X, 1 - v.texcoord.Y);
v.texcoord = new Vector2(v.texcoord.X, 1 - v.texcoord.Y);
//v.texcoord = new Vector2(1 - v.texcoord.X, v.texcoord.Y);
}
PSOutput OUT = new PSOutput();
Vector4 col = v.color;
if ((shaderContext.shadeMode == ShadeMode.Lighting ||
shaderContext.shadeMode == ShadeMode.NDotL) &&
shaderContext.light != null)
{
Vector3 normalWorld = v.normalWorld;
normalWorld = Vector3.Normalize(normalWorld);
Vector3 lightDir = shaderContext.light.lightDirForShader;
//Lambert Lighting
float NDotL = Vector3.Dot(normalWorld, lightDir);
NDotL = Utils.Clamp(NDotL, 0, 1);
if (shaderContext.shadeMode == ShadeMode.Lighting && texture != null)
{
Vector4 tex = texture.Tex2D(v.texcoord, shaderContext.textureFilterMode);
col = tex * (NDotL * shaderContext.light.lightColor + shaderContext.ambient);
}
else
{
col = new Vector4(NDotL, NDotL, NDotL, 1f);
}
}
else if (shaderContext.shadeMode == ShadeMode.Texture && texture != null)
{
col = texture.Tex2D(v.texcoord, shaderContext.textureFilterMode);
}
//col = new Vector4(v.texcoord.X, v.texcoord.Y, 0, 1 );
OUT.color = col;
return(OUT);
}
bool FrontEndCullingByAngle(VSOutput v0, VSOutput v1, VSOutput v2)
{
if (context.frontEndCull == FrontEndCull.Off)
{
return(true);
}
if (context.cullMode == CullMode.None)
{
return(true);
}
Vector3 pos0 = new Vector3(v0.position.X, v0.position.Y, v0.position.Z);
Vector3 pos1 = new Vector3(v1.position.X, v1.position.Y, v1.position.Z);
Vector3 pos2 = new Vector3(v2.position.X, v2.position.Y, v2.position.Z);
//为什么把Z改成Eye Space的Z就是对的？
//pos0.Z = v0.position.W;
//pos1.Z = v1.position.W;
//pos2.Z = v2.position.W;
//Vector3 n = Vector3.Cross(pos1-pos0, pos2 - pos0);
Vector3 n = Vector3.Cross(pos1 - pos0, pos2 - pos1);
Vector3 p = pos0;
Vector3 test = Vector3.Cross(new Vector3(1, 0, 0), new Vector3(0, 1, 0));
//n = Vector3.Normalize(n);
//p = Vector3.Normalize(p);
float cos = Vector3.Dot(n, p);
if (context.winding == Winding.Clockwise)
{
return(cos <= 0);
}
return(cos >= 0);
}
bool BackfaceCulling(VSOutput vScreen0, VSOutput vScreen1, VSOutput vScreen2)
{
if (context.cullMode == CullMode.None)
{
return(true);
}
if (context.frontEndCull == FrontEndCull.On)
{
return(true);
}
Vector2 p0 = new Vector2(vScreen0.posScreen.X, vScreen0.posScreen.Y);
Vector2 p1 = new Vector2(vScreen1.posScreen.X, vScreen1.posScreen.Y);
Vector2 p2 = new Vector2(vScreen2.posScreen.X, vScreen2.posScreen.Y);
float area = Rasterizer.EdgeFunction(p0, p1, p2);
if (context.winding == Winding.Clockwise)
{
return(area < 0);
}
//在Viewport Space, 由于Y轴向下, area > 0表示逆时针
return(area > 0);
}
public void BarycentricRasterizeTriangle(VSOutput v0, VSOutput v1, VSOutput v2)
{
int width = context.frameSize.Width;
int height = context.frameSize.Height;
Vector2 xy0 = new Vector2(v0.posScreen.X, v0.posScreen.Y);
Vector2 xy1 = new Vector2(v1.posScreen.X, v1.posScreen.Y);
Vector2 xy2 = new Vector2(v2.posScreen.X, v2.posScreen.Y);
float z0 = v0.posScreen.Z;
float z1 = v1.posScreen.Z;
float z2 = v2.posScreen.Z;
//求包围盒
float xmin = Math.Min(Math.Min(xy0.X, xy1.X), xy2.X);
float xmax = Math.Max(Math.Max(xy0.X, xy1.X), xy2.X);
float ymin = Math.Min(Math.Min(xy0.Y, xy1.Y), xy2.Y);
float ymax = Math.Max(Math.Max(xy0.Y, xy1.Y), xy2.Y);
//像素坐标包围盒
int x0 = Utils.Clamp((int)xmin, 0, width - 1);
int y0 = Utils.Clamp((int)ymin, 0, height - 1);
int x1 = Utils.Clamp((int)xmax, 0, width - 1);
int y1 = Utils.Clamp((int)ymax, 0, height - 1);
for (int y = y0; y <= y1; ++y)
{
for (int x = x0; x <= x1; ++x)
{
//加0.5取像素的中间位置的坐标
Vector2 pixel = new Vector2(x + 0.5f, y + 0.5f);
Vector3 w = BarycentricCoordinates(pixel, xy0, xy1, xy2);
float w0 = w.X; float w1 = w.Y; float w2 = w.Z;
if (!(w0 >= 0 && w1 >= 0 && w2 >= 0))
{
//像素点不在三角形内
continue;
}
context.statics.fragmentCount += 1;
//深度测试
float depth = w0 * z0 + w1 * z1 + w2 * z2;
if (context.depthBuffer[x, y] < depth)
{
continue;
}
Color col;
if (context.drawMode == DrawMode.Depth)
{
Vector4 depthColor = new Vector4(depth, depth, depth, 1);
col = Utils.VectorToColor(depthColor);
}
else
{
//正常渲染
//插值UV等顶点属性
float fInvW = w0 * v0.position.W + w1 * v1.position.W + w2 * v2.position.W;
//由于position.W是1/W = 1/-Z_Eye
float Z_Eye = 1f / fInvW;
Vector2 uv = w0 * v0.texcoord + w1 * v1.texcoord + w2 * v2.texcoord;
uv *= Z_Eye;
Vector4 color = w0 * v0.color + w1 * v1.color + w2 * v2.color;
color *= Z_Eye;
Vector3 normalWorld = w0 * v0.normalWorld + w1 * v1.normalWorld + w2 * v2.normalWorld;
if (shader != null)
{
VSOutput fragment = new VSOutput();
//v.position =
fragment.normalWorld = normalWorld;
fragment.texcoord = uv;
fragment.color = color;
PSOutput OUT = shader.FragShader(fragment);
if (OUT.isDiscard)
{
continue;
}
col = Utils.VectorToColor(OUT.color);
}
else
{
col = Utils.VectorToColor(color);
}
}
context.depthBuffer[x, y] = depth;
DrawPixel(x, y, col);
}
}
}
bool FrontEndCulling(VSOutput v0, VSOutput v1, VSOutput v2)
{
return(FrontEndCullingByArea(v0, v1, v2));
//return FrontEndCullingByAngle(v0, v1, v2);
}
