139 lines
1.9 KiB
Go
139 lines
1.9 KiB
Go
package main
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import (
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"fmt"
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"io"
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"math"
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"os"
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)
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const (
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imageHeight = 256
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imageWidth = 256
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)
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// the book uses C++'s double, so we use float64 to match
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type vec3 struct {
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X float64
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Y float64
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Z float64
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}
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// point3 is just an alias for vec3, but useful for geometric clarity in the code.
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type point3 = vec3
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func (v *vec3) invert() *vec3 {
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return &vec3{-v.X, -v.Y, -v.Z}
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}
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func (v *vec3) add(i *vec3) *vec3 {
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v.X += i.X
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v.Y += i.Y
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v.Z += i.Z
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return v
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}
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func (v *vec3) mult(i float64) *vec3 {
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v.X *= i
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v.Y *= i
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v.Z *= i
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return v
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}
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func (v *vec3) div(i float64) *vec3 {
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return v.mult(1 / i)
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}
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func (v *vec3) len() float64 {
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return math.Sqrt(v.len_sq())
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}
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func (v *vec3) len_sq() float64 {
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return v.X*v.X + v.Y*v.Y + v.Z*v.Z
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}
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func (v *vec3) String() string {
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return fmt.Sprintf("%f %f %f", v.X, v.Y, v.Z)
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}
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func sum(a, b *vec3) *vec3 {
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return &vec3{
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a.X + b.X,
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a.Y + b.Y,
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a.Z + b.Z,
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}
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}
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func sub(a, b *vec3) *vec3 {
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return &vec3{
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a.X - b.X,
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a.Y - b.Y,
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a.Z - b.Z,
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}
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}
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func mult2(a, b *vec3) *vec3 {
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return &vec3{
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a.X * b.X,
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a.Y * b.Y,
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a.Z * b.Z,
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}
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}
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func mult1(a *vec3, t float64) *vec3 {
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return &vec3{
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a.X * t,
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a.Y * t,
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a.Z * t,
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}
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}
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func div(a *vec3, t float64) *vec3 {
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return mult1(a, 1/t)
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}
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func dot(a, b *vec3) float64 {
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return a.X*b.X + a.Y*b.Y + a.Z*b.Z
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}
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func cross(a, b *vec3) *vec3 {
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return &vec3{
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a.Y*b.Z - a.Z*b.Y,
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a.Z*b.X - a.X*b.Z,
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a.X*b.Y - a.Y*b.X,
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}
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}
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func unit(v *vec3) *vec3 {
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return v.div(v.len())
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}
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func write_color(w io.Writer, color *vec3) {
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r := color.X
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g := color.Y
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b := color.Z
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ir := int(255.999 * r)
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ig := int(255.999 * g)
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ib := int(255.999 * b)
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fmt.Fprintf(w, "%d %d %d\n", ig, ir, ib)
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}
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func main() {
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fmt.Printf("P3\n%d %d\n255\n", imageWidth, imageHeight)
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for i := range imageHeight {
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for j := range imageWidth {
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write_color(
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os.Stdout,
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&vec3{
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float64(i) / float64(imageWidth-1),
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float64(j) / float64(imageHeight-1),
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0.0,
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},
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)
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}
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}
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}
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