diff --git a/internal/atlas/image.go b/internal/atlas/image.go
index be134b5e8..97e8a9eb3 100644
--- a/internal/atlas/image.go
+++ b/internal/atlas/image.go
@@ -59,7 +59,7 @@ func temporaryPixelsByteSize(size int) int {
 // Be careful that the returned pixels might not be zero-cleared.
 func (t *temporaryPixels) alloc(size int) []byte {
 	if len(t.pixels) < t.pos+size {
-		t.pixels = make([]byte, temporaryPixelsByteSize(t.pos+size))
+		t.pixels = make([]byte, max(len(t.pixels)*2, temporaryPixelsByteSize(size)))
 		t.pos = 0
 	}
 	pix := t.pixels[t.pos : t.pos+size]
diff --git a/internal/graphics/vertex.go b/internal/graphics/vertex.go
index 8ea28fa5f..defb980d8 100644
--- a/internal/graphics/vertex.go
+++ b/internal/graphics/vertex.go
@@ -75,13 +75,20 @@ func verticesBackendFloat32Size(size int) int {
 	return l
 }
 
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
 func (v *verticesBackend) slice(n int) []float32 {
 	v.m.Lock()
 	defer v.m.Unlock()
 
 	need := n * VertexFloatNum
 	if len(v.backend) < v.pos+need {
-		v.backend = make([]float32, verticesBackendFloat32Size(v.pos+need))
+		v.backend = make([]float32, max(len(v.backend)*2, verticesBackendFloat32Size(need)))
 		v.pos = 0
 	}
 	s := v.backend[v.pos : v.pos+need]