feat(文件拆分): 拆分几何三维基础能力

internal/base/threed/u3d_view_render.go

@@ -0,0 +1,103 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package threed
+
+import (
+	"fmt"
+	"image"
+	"math"
+)
+
+// viewLayers 按ECMA-363第9.5.4节依次绘制背景层或覆盖层
+// 入参: layers 按后至前排列的纹理层
+// 返回: error 参数、资源、预算或取消错误
+func (r *Renderer) viewLayers(layers []U3DViewLayer) error {
+	for _, layer := range layers {
+		if err := r.ctx.Err(); err != nil {
+			return err
+		}
+		for _, value := range [...]float32{layer.Blend, layer.Rotation, layer.Location[0], layer.Location[1], layer.Scale[0], layer.Scale[1]} {
+			if !finite(float64(value)) {
+				return fmt.Errorf("invalid U3D view layer values")
+			}
+		}
+		texture, err := r.texture(layer.Texture)
+		if err != nil {
+			return err
+		}
+		blend := min(1, max(0, float64(layer.Blend)))
+		if blend == 0 || layer.Scale[0] == 0 || layer.Scale[1] == 0 {
+			continue
+		}
+		sin, cos := math.Sincos(float64(layer.Rotation))
+		x, y := float64(layer.Location[0]), float64(layer.Location[1])
+		if r.view.Attributes&1 != 0 {
+			x *= float64(r.output.Rect.Dx())
+			y *= float64(r.output.Rect.Dy())
+		}
+		sx, sy := float64(layer.Scale[0]), float64(layer.Scale[1])
+		rx, ry := float64(layer.Registration[0]), float64(layer.Registration[1])
+		m := [6]float64{cos * sx, -sin * sx, sin * sy, cos * sy, x - cos*sx*rx - sin*sy*ry, y + sin*sx*rx - cos*sy*ry}
+		bounds := viewImageBounds(texture.Bounds(), m, r.output.Bounds())
+		for py := bounds.Min.Y; py < bounds.Max.Y; py++ {
+			for px := bounds.Min.X; px < bounds.Max.X; px++ {
+				if px%4096 == 0 || px == bounds.Min.X {
+					if err := r.ctx.Err(); err != nil {
+						return err
+					}
+				}
+				cx, cy := float64(px)+.5, float64(py)+.5
+				if cx < r.viewport[0] || cy < r.viewport[1] || cx >= r.viewport[0]+r.viewport[2] || cy >= r.viewport[1]+r.viewport[3] {
+					continue
+				}
+				dx, dy := cx-x, cy-y
+				u, v := (cos*dx-sin*dy)/sx+rx, (sin*dx+cos*dy)/sy+ry
+				if u < 0 || v < 0 || u >= float64(texture.Rect.Dx()) || v >= float64(texture.Rect.Dy()) {
+					continue
+				}
+				value := u3dTextureSample(texture, u, v)
+				pixel := &r.frame[py*r.output.Rect.Dx()+px]
+				alpha := value[3] * blend
+				for i := range pixel.color {
+					pixel.color[i] = value[i]*blend + pixel.color[i]*(1-alpha)
+				}
+			}
+		}
+	}
+	return r.ctx.Err()
+}
+
+// u3dTextureSample 在像素中心进行双线性采样，使用预乘颜色避免透明边缘色晕
+// 入参: texture 纹理, x 横向像素坐标, y 纵向像素坐标
+// 返回: [4]float64 预乘颜色及透明度
+func u3dTextureSample(texture *image.NRGBA64, x, y float64) [4]float64 {
+	x, y = x-.5, y-.5
+	x0, y0 := int(math.Floor(x)), int(math.Floor(y))
+	fx, fy := x-float64(x0), y-float64(y0)
+	wx, wy := [2]float64{1 - fx, fx}, [2]float64{1 - fy, fy}
+	var result [4]float64
+	for row := range 2 {
+		for col := range 2 {
+			weight := wx[col] * wy[row]
+			c := texture.NRGBA64At(min(max(0, x0+col), texture.Rect.Max.X-1), min(max(0, y0+row), texture.Rect.Max.Y-1))
+			alpha := float64(c.A) / 65535
+			result[0] += float64(c.R) / 65535 * alpha * weight
+			result[1] += float64(c.G) / 65535 * alpha * weight
+			result[2] += float64(c.B) / 65535 * alpha * weight
+			result[3] += alpha * weight
+		}
+	}
+	return result
+}