58 lines
1.1 KiB
Go
58 lines
1.1 KiB
Go
package main
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import (
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"image"
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"image/color"
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"math"
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)
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// GenerateBumpMap creates a bump map from a heightmap.
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func GenerateBumpMap(heightmap *image.RGBA, width, height int, depth float64) *image.RGBA {
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bumpMap := image.NewRGBA(image.Rect(0, 0, width, height))
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sobelX := [][]int{
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{-1, 0, 1},
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{-2, 0, 2},
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{-1, 0, 1},
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}
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sobelY := [][]int{
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{-1, -2, -1},
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{0, 0, 0},
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{1, 2, 1},
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}
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for y := 1; y < height-1; y++ {
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for x := 1; x < width-1; x++ {
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var gx, gy float64
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for i := 0; i < 3; i++ {
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for j := 0; j < 3; j++ {
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gray, _, _, _ := heightmap.At(x+i-1, y+j-1).RGBA()
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intensity := float64(gray >> 8)
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gx += intensity * float64(sobelX[j][i])
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gy += intensity * float64(sobelY[j][i])
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}
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}
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nx := gx
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ny := gy
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nz := 1.0 / depth
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length := math.Sqrt(nx*nx + ny*ny + nz*nz)
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if length > 0 {
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nx /= length
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ny /= length
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nz /= length
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}
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r := uint8((nx + 1.0) * 127.5)
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g := uint8((ny + 1.0) * 127.5)
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b := uint8(nz * 255.0)
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bumpMap.Set(x, y, color.RGBA{R: r, G: g, B: b, A: 255})
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}
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}
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return bumpMap
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}
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