go-opengl-pixel/pixelgl/attr.go

95 lines
1.9 KiB
Go

package pixelgl
// AttrFormat defines names and types of OpenGL attributes (vertex format, uniform format, etc.).
//
// Example:
// AttrFormat{"position": Vec2, "color": Vec4, "texCoord": Vec2}
type AttrFormat map[string]AttrType
// Contains checks whether a format contains a specific attribute.
//
// It does a little more than a hard check: e.g. if you query a Vec2 attribute, but the format contains Vec3,
// Contains returns true, because Vec2 is assignable to Vec3. Specifically, Float -> Vec2 -> Vec3 -> Vec4 (transitively).
// This however does not work for matrices or ints.
func (af AttrFormat) Contains(attr Attr) bool {
if typ, ok := af[attr.Name]; ok {
if (Float <= typ && typ <= Vec4) && (Float <= attr.Type && attr.Type <= typ) {
return true
}
return attr.Type == typ
}
return false
}
// Size returns the total size of all attributes of an attribute format.
func (af AttrFormat) Size() int {
total := 0
for _, typ := range af {
total += typ.Size()
}
return total
}
// Attr represents an arbitrary OpenGL attribute, such as a vertex attribute or a shader uniform attribute.
type Attr struct {
Name string
Type AttrType
}
// AttrType represents the type of an OpenGL attribute.
type AttrType int
// List of all possible attribute types.
const (
Int AttrType = iota
Float
Vec2
Vec3
Vec4
Mat2
Mat23
Mat24
Mat3
Mat32
Mat34
Mat4
Mat42
Mat43
)
// Size returns the size of a type in bytes.
func (at AttrType) Size() int {
switch at {
case Int:
return 4
case Float:
return 4
case Vec2:
return 2 * 4
case Vec3:
return 3 * 4
case Vec4:
return 4 * 4
case Mat2:
return 2 * 2 * 4
case Mat23:
return 2 * 3 * 4
case Mat24:
return 2 * 4 * 4
case Mat3:
return 3 * 3 * 4
case Mat32:
return 3 * 2 * 4
case Mat34:
return 3 * 4 * 4
case Mat4:
return 4 * 4 * 4
case Mat42:
return 4 * 2 * 4
case Mat43:
return 4 * 3 * 4
default:
panic("size of vertex attribute type: invalid type")
}
}