render: move render_world_helper, remove chunks drawn behind view

internal/world/render.go

@@ -6,6 +6,7 @@ import (
 	"unsafe"
 
 	"edgaru089.ml/go/gl01/internal/asset"
+	"edgaru089.ml/go/gl01/internal/io"
 	"edgaru089.ml/go/gl01/internal/util/itype"
 	"github.com/go-gl/gl/all-core/gl"
 )
@@ -67,14 +68,45 @@ func (c *Chunk) updateRender() {
 
 	select {
 	case vert := <-c.vertUpdate:
-		log.Printf("Chunk [%d,%d]: received len=%d", c.X, c.Z, len(vert))
 		gl.BufferData(gl.ARRAY_BUFFER, int(unsafe.Sizeof(Vertex{}))*len(vert), gl.Ptr(vert), gl.DYNAMIC_DRAW)
 		c.vbolen = len(vert)
 	default: // do nothing
 	}
 }
 
+var checkViewOffset = []itype.Vec3d{
+	{0, 0, 0},
+	{ChunkSizeX, 0, 0},
+	{0, 0, ChunkSizeZ},
+	{ChunkSizeX, 0, ChunkSizeZ},
+	{0, ChunkSizeY, 0},
+	{ChunkSizeX, ChunkSizeY, 0},
+	{0, ChunkSizeY, ChunkSizeZ},
+	{ChunkSizeX, ChunkSizeY, ChunkSizeZ},
+}
+
+// checkView checks if the chunk is in the front-facing direction of the view.
+func (c *Chunk) checkView(from, facing itype.Vec3d) bool {
+	off := itype.Vec3d{
+		float64(c.X * ChunkSizeX),
+		0,
+		float64(c.Z * ChunkSizeZ),
+	}
+
+	for _, check := range checkViewOffset {
+		ok := off.Add(check).Add(from.Negative()).Dot(facing) > 0
+		if ok {
+			return true
+		}
+	}
+	return false
+}
+
 func (c *Chunk) Render() {
+	if !c.checkView(io.ViewPos, io.ViewDir) || !c.checkView(io.RenderPos, io.RenderDir) {
+		return
+	}
+
 	c.Bind()
 	c.updateRender()
 	gl.DrawArrays(gl.TRIANGLES, 0, int32(c.vbolen))