private void CreateShader()
{
m_BlinnPhongShader = new BlinnPhongShader();
}
private void RasterTriangle(Vertex v0, Vertex v1, Vertex v2)
{
// 模型变换:记录世界空间的坐标，计算光照时使用
Vector3 v0_world = m_Model.MultiplyPoint(v0.position);
Vector3 v1_world = m_Model.MultiplyPoint(v1.position);
Vector3 v2_world = m_Model.MultiplyPoint(v2.position);
// View变换:记录观察空间中的深度，Unity中向量和矩阵相乘直接就变换成三个分量的向量了
Vector3 v0_view = m_View.MultiplyPoint(v0_world);
Vector3 v1_view = m_View.MultiplyPoint(v1_world);
Vector3 v2_view = m_View.MultiplyPoint(v2_world);
// 投影变换
Vector3 v0_NDC = m_Projection.MultiplyPoint(v0_view);
Vector3 v1_NDC = m_Projection.MultiplyPoint(v1_view);
Vector3 v2_NDC = m_Projection.MultiplyPoint(v2_view);
// Clip
if (v0_NDC.x < -1 || v0_NDC.x > 1 || v0_NDC.y < -1 || v0_NDC.y > 1 || v0_NDC.z < -1 || v0_NDC.z > 1 ||
v1_NDC.x < -1 || v1_NDC.x > 1 || v1_NDC.y < -1 || v1_NDC.y > 1 || v1_NDC.z < -1 || v1_NDC.z > 1 ||
v2_NDC.x < -1 || v2_NDC.x > 1 || v2_NDC.y < -1 || v2_NDC.y > 1 || v2_NDC.z < -1 || v2_NDC.z > 1)
{
return;
}
// Cull,Unity中三角形顺时针为正面,向量叉乘的方向在右手坐标系中使用右手定则确定，在左手坐标系中使用左手定则确定。
// 这里需要注意不管是在右手坐标系还是左手坐标系，叉乘向量的数值结果是一样的，只不过表示的绝对向量方向不同，Unity中是左手坐标系，遵循左手定则。
if (m_CullType == CullType.Back)
{
Vector3 v0v1 = v1_NDC - v0_NDC;
Vector3 v0v2 = v2_NDC - v0_NDC;
if (Vector3.Cross(v0v1, v0v2).z > 0)
{
return;
}
}
if (m_CullType == CullType.Front)
{
Vector3 v0v1 = v1_NDC - v0_NDC;
Vector3 v0v2 = v2_NDC - v0_NDC;
if (Vector3.Cross(v0v1, v0v2).z < 0)
{
return;
}
}
// Viewport
Vector3 v0_screen = new Vector3((v0_NDC.x + 1) / 2 * width, (v0_NDC.y + 1) / 2 * height, 0);
Vector3 v1_screen = new Vector3((v1_NDC.x + 1) / 2 * width, (v1_NDC.y + 1) / 2 * height, 0);
Vector3 v2_screen = new Vector3((v2_NDC.x + 1) / 2 * width, (v2_NDC.y + 1) / 2 * height, 0);
// Triagnle Bounding Box
Vector2Int bboxMin = new Vector2Int((int)Mathf.Min(Mathf.Min(v0_screen.x, v1_screen.x), v2_screen.x),
(int)Mathf.Min(Mathf.Min(v0_screen.y, v1_screen.y), v2_screen.y));
Vector2Int bboxMax = new Vector2Int((int)(Mathf.Max(Mathf.Max(v0_screen.x, v1_screen.x), v2_screen.x) + 0.5f),
(int)(Mathf.Max(Mathf.Max(v0_screen.y, v1_screen.y), v2_screen.y) + 0.5f));
for (int i = bboxMin.x; i < bboxMax.x; i++)
{
for (int j = bboxMin.y; j < bboxMax.y; j++)
{
// Edge Function
if (IsInsideTriangle(i + 0.5f, j + 0.5f, v0_screen, v1_screen, v2_screen))
{
// 计算重心坐标
Vector3 barycentricCoordinate = BarycentricCoordinate(i + 0.5f, j + 0.5f, v0_screen, v1_screen, v2_screen);
// 计算该像素在观察空间的深度值:观察空间中的z的倒数在屏幕空间是线性的，所以用重心坐标可以插值z的倒数，再进行转换求出该像素的观察空间中的深度
float z_view = 1.0f / (barycentricCoordinate.x / v0_view.z + barycentricCoordinate.y / v1_view.z + barycentricCoordinate.z / v2_view.z);
// 插值投影后的z，首先投影后的z除以观察空间的z，用重心坐标插值后，再乘该像素观察空间的z
float z_interpolated = z_view * (v0_NDC.z / v0_view.z * barycentricCoordinate.x +
v1_NDC.z / v1_view.z * barycentricCoordinate.y +
v2_NDC.z / v2_view.z * barycentricCoordinate.z);
// Early-Z :)
// 存储到Depth Buffer，从[-1,1]变换到[0,1]
float z01 = (z_interpolated + 1) / 2f;
if (z01 > m_FrameBuffer.GetDepth(i, j))
{
continue;
}
else
{
m_FrameBuffer.SetDepth(i, j, z01);
}
// 插值顶点属性：颜色、uv、法线、副切线、世界坐标
Color color = z_view * (v0.color / v0_view.z * barycentricCoordinate.x +
v1.color / v1_view.z * barycentricCoordinate.y +
v2.color / v2_view.z * barycentricCoordinate.z);
Vector2 uv = z_view * (v0.uv / v0_view.z * barycentricCoordinate.x +
v1.uv / v1_view.z * barycentricCoordinate.y +
v2.uv / v2_view.z * barycentricCoordinate.z);
Vector3 normal = z_view * (v0.normal / v0_view.z * barycentricCoordinate.x +
v1.normal / v1_view.z * barycentricCoordinate.y +
v2.normal / v2_view.z * barycentricCoordinate.z);
Vector4 tangent = z_view * (v0.tangent / v0_view.z * barycentricCoordinate.x +
v1.tangent / v1_view.z * barycentricCoordinate.y +
v2.tangent / v2_view.z * barycentricCoordinate.z);
Vector3 worldPos = z_view * (v0_world / v0_view.z * barycentricCoordinate.x +
v1_world / v1_view.z * barycentricCoordinate.y +
v2_world / v2_view.z * barycentricCoordinate.z);
Color col = Color.black;
if (m_CurShader != null)
{
m_CurShader.modelMatrix = m_Model;
m_CurShader.vertexColor = color;
m_CurShader.uv = uv;
m_CurShader.normal = normal;
m_CurShader.tangent = tangent;
if (m_CurShader is BlinnPhongShader)
{
BlinnPhongShader blinnPhongShader = (BlinnPhongShader)m_CurShader;
blinnPhongShader.worldPos = worldPos;
foreach (var light in m_Lights)
{
blinnPhongShader.lightColor = light.color;
blinnPhongShader.lightIntensity = light.intensity;
blinnPhongShader.lightPos = light.transform.position;
col += blinnPhongShader.FragmentShade();
}
}
}
m_FrameBuffer.SetColor(i, j, col);
}
}
}
}
