Method NewGeometry

loader/obj/obj.go:312–369

NewGeometry generates and returns a geometry from the specified object

(obj *Object)

// NewGeometry generates and returns a geometry from the specified object
func (dec *Decoder) NewGeometry(obj *Object) (*geometry.Geometry, error) {

	geom := geometry.NewGeometry()

	// Create buffers
	positions := math32.NewArrayF32(0, 0)
	normals := math32.NewArrayF32(0, 0)
	uvs := math32.NewArrayF32(0, 0)
	indices := math32.NewArrayU32(0, 0)

	// copy all vertex info from the decoded Object, face and index to the geometry
	copyVertex := func(face *Face, idx int) {
		var vec3 math32.Vector3
		var vec2 math32.Vector2

		pos := positions.Size() / 3
		// Copy vertex position and append to geometry
		dec.Vertices.GetVector3(3*face.Vertices[idx], &vec3)
		positions.AppendVector3(&vec3)
		// Copy vertex normal and append to geometry
		if face.Normals[idx] != invINDEX {
			dec.Normals.GetVector3(3*face.Normals[idx], &vec3)
			normals.AppendVector3(&vec3)
		}
		// Copy vertex uv and append to geometry
		if face.Uvs[idx] != invINDEX {
			dec.Uvs.GetVector2(2*face.Uvs[idx], &vec2)
			uvs.AppendVector2(&vec2)
		}
		indices.Append(uint32(pos))
	}

	var group *geometry.Group
	matName := ""
	matIndex := 0
	for _, face := range obj.Faces {
		// If face material changed, starts a new group
		if face.Material != matName {
			group = geom.AddGroup(indices.Size(), 0, matIndex)
			matName = face.Material
			matIndex++
		}
		// Copy face vertices to geometry
		for idx := 1; idx < len(face.Vertices)-1; idx++ {
			copyVertex(&face, 0)
			copyVertex(&face, idx)
			copyVertex(&face, idx+1)
			group.Count += 3
		}
	}

	geom.SetIndices(indices)
	geom.AddVBO(gls.NewVBO(positions).AddAttrib(gls.VertexPosition))
	geom.AddVBO(gls.NewVBO(normals).AddAttrib(gls.VertexNormal))
	geom.AddVBO(gls.NewVBO(uvs).AddAttrib(gls.VertexTexcoord))

	return geom, nil
}