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); } }