Implement Home View

1 files changed, 47 insertions, 0 deletions

diff --git a/geometry.go b/geometry.go
index 04896dc..1fc516a 100644
--- a/geometry.go
+++ b/geometry.go
@@ -2,6 +2,10 @@
 
 package main
 
+import (
+	"github.com/go-gl/mathgl/mgl32"
+)
+
 // representation of a three-dimensional point in space
 type Point struct {
 	scalars [3]float32  // x = scalars[0], y = scalars[1], z = scalars[2]
@@ -17,3 +21,46 @@ type Surface struct {
 	triangles []*Triangle
 }
 
+// return a transformation to view the whole centered surface
+func (s Surface) getHomeView() mgl32.Mat4 {
+
+	// evaluating the smallest and biggest values for x,y,z of the surface
+	var min,max [3]float32
+	for _,triangle := range(s.triangles) {
+		for _,point := range(triangle.points) {
+			for index,_ := range(min) {
+				if point.scalars[index] < min[index] {
+					min[index] = point.scalars[index]
+				}
+				if point.scalars[index] > max[index] {
+					max[index] = point.scalars[index]
+				}
+			}
+		}
+	}
+
+	// calculate center point
+	var center Point
+	for index,_ := range(min) {
+		center.scalars[index] = (min[index] + max[index]) / 2
+	}
+
+	// calculate zoom
+	var zoom,zoomX,zoomY float32
+	const fillFactor float32 = 0.8
+	zoomX = (2 / (max[0] - min[0])) * fillFactor
+	zoomY = (2 / (max[1] - min[1])) * fillFactor
+	if zoomX > zoomY {
+		zoom = zoomY
+	} else {
+		zoom = zoomX
+	}
+
+	// calculate and return transformation
+	var trafo mgl32.Mat4 = mgl32.Ident4()
+	trafo = mgl32.Translate3D(-center.scalars[0], -center.scalars[1], -center.scalars[2]).Mul4(trafo)
+	trafo = mgl32.Scale3D(zoom, zoom, zoom).Mul4(trafo)
+
+	return trafo
+}
+