Implement renderer reset cheaper ... and this time correctly.

common/renderer.go

@@ -137,7 +137,7 @@ func NewRenderer(width, height int, transparent bool) (renderer *Renderer) {
 		tBuffer: tBuffer,
 		spans:   spans}
 
-	renderer.Reset()
+	renderer.initBuffers()
 	return
 }
 
@@ -146,16 +146,7 @@ func (r *Renderer) SetPos(xOfs, zOfs int16) {
 	r.zOfs = zOfs
 }
 
-func (r *Renderer) Reset() {
-
-	/* TODO: Figure out why this early stop results
-	   in broken renderings.
-
-	if r.IsEmpty() {
-		return
-	}
-	*/
-
+func (r *Renderer) initBuffers() {
 	yb := r.yBuffer
 	yb = yb[:len(yb)]
 	for i := range yb {
@@ -173,9 +164,20 @@ func (r *Renderer) Reset() {
 	for i := range ym {
 		ym[i] = math.MinInt32
 	}
+}
+
+func (r *Renderer) Reset() {
+
+	r.RejectedBlocks = 0
+
+	if r.SolidBlocks > 0 || r.TransparentBlocks > 0 {
+		r.SolidBlocks = 0
+		r.initBuffers()
+	}
 
 	if r.TransparentBlocks > 0 {
 		r.TransparentBlocks = 0
+
 		tb := r.tBuffer
 		for i, t := range tb {
 			if t != nil {
@@ -184,8 +186,6 @@ func (r *Renderer) Reset() {
 			}
 		}
 	}
-	r.SolidBlocks = 0
-	r.RejectedBlocks = 0
 }
 
 func (r *Renderer) IsFilled() bool {