ext/texturetransform/transform.go
package texturetransform
import (
"bytes"
"encoding/json"
"github.com/qmuntal/gltf"
)
var (
// DefaultScale defines a scaling that does not modify the size of the object.
DefaultScale = [2]float64{1, 1}
emptyScale = [2]float64{0, 0}
emptyOffset = [2]float64{0, 0}
)
const (
// ExtensionName defines the ExtTextureTransform unique key.
ExtensionName = "KHR_texture_transform"
)
// Unmarshal decodes the json data into the correct type.
func Unmarshal(data []byte) (any, error) {
t := new(TextureTranform)
err := json.Unmarshal(data, t)
return t, err
}
func init() {
gltf.RegisterExtension(ExtensionName, Unmarshal)
}
// TextureTranform can be used in textureInfo to pack many low-res texture into a single large texture atlas.
type TextureTranform struct {
Offset [2]float64 `json:"offset"`
Rotation float64 `json:"rotation,omitempty"`
Scale [2]float64 `json:"scale"`
TexCoord *uint32 `json:"texCoord,omitempty"`
}
// ScaleOrDefault returns the node scale if it represents a valid scale factor, else return the default one.
func (t *TextureTranform) ScaleOrDefault() [2]float64 {
if t.Scale == emptyScale {
return DefaultScale
}
return t.Scale
}
// UnmarshalJSON unmarshal the pbr with the correct default values.
func (t *TextureTranform) UnmarshalJSON(data []byte) error {
type alias TextureTranform
tmp := alias(TextureTranform{Scale: DefaultScale})
err := json.Unmarshal(data, &tmp)
if err == nil {
*t = TextureTranform(tmp)
}
return err
}
// MarshalJSON marshal the pbr with the correct default values.
func (t *TextureTranform) MarshalJSON() ([]byte, error) {
type alias TextureTranform
out, err := json.Marshal(&struct{ *alias }{alias: (*alias)(t)})
if err == nil {
if t.Scale == DefaultScale {
out = removeProperty([]byte(`"scale":[1,1]`), out)
} else if t.Scale == emptyScale {
out = removeProperty([]byte(`"scale":[0,0]`), out)
}
if t.Offset == emptyOffset {
out = removeProperty([]byte(`"offset":[0,0]`), out)
}
out = sanitizeJSON(out)
}
return out, err
}
func removeProperty(str []byte, b []byte) []byte {
b = bytes.Replace(b, str, []byte(""), 1)
return bytes.Replace(b, []byte(`,,`), []byte(","), 1)
}
func sanitizeJSON(b []byte) []byte {
b = bytes.Replace(b, []byte(`{,`), []byte("{"), 1)
return bytes.Replace(b, []byte(`,}`), []byte("}"), 1)
}